Validation of predictive equations to estimate resting metabolic rate of females and males across different activity levels

OBJECTIVES

Using equations to predict resting metabolic rate (RMR) has yielded different degrees of validity, particularly when sex and different physical activity levels were considered. Therefore, the purpose of the present study was to determine the validity of several different predictive equations to estimate RMR in female and male adults with varying physical activity levels.

METHOD

We measured the RMR of 50 adults (26 females and 24 males) evenly distributed through activity levels varying from sedentary to ultra-endurance. Body composition was measured by dual X-ray absorptiometry and physical activity was monitored by accelerometry. Ten equations to predict RMR were applied (using Body Mass [BM]: Harris & Benedict, 1919; Mifflin et al., 1990 [MifflinBM]; Pontzer et al., 2021 [PontzerBM]; Schofield, 1985; FAO/WHO/UNU, 2004; and using Fat-Free Mass (FFM): Cunningham, 1991; Johnstone et al., 2006; Mifflin et al., 1990 [MifflinFFM]; Nelson et al. 1992; Pontzer et al., 2021 [PontzerFFM]). The accuracy of these equations was analyzed, and the effect of sex and physical activity was evaluated using different accuracy metrics.

RESULTS

Equations using BM were less accurate for females, and their accuracy was influenced by physical activity and body composition. FFM equations were slightly less accurate for males but there was no obvious effect of physical activity or other sample parameters. PontzerFFM provides higher accuracy than other models independent of the magnitude of RMR, sex, activity levels, and sample characteristics.

CONCLUSION

Equations using FFM were more accurate than BM equations in our sample. Future studies are needed to test the accuracy of RMR prediction equations in diverse samples.

Ultra-processed food intake, gut microbiome, and glucose homeostasis in mid-life adults: Background, design, and methods of a controlled feeding trial

BACKGROUND

Aging is associated with gut dysbiosis, low-grade inflammation, and increased risk of type 2 diabetes (T2D). Prediabetes, which increases T2D and cardiovascular disease risk, is present in 45-50% of mid-life adults. The gut microbiota may link ultra-processed food (UPF) with inflammation and T2D risk.

METHODS

Following a 2-week standardized lead-in diet (59% UPF), adults aged 40-65 years will be randomly assigned to a 6-week diet emphasizing either UPF (81% total energy) or non-UPF (0% total energy). Measurements of insulin sensitivity, 24-h and postprandial glycemic control, gut microbiota composition/function, fecal short chain fatty acids, intestinal inflammation, inflammatory cytokines, and vascular function will be made before and following the 6-week intervention period. Prior to recruitment, menus were developed in order to match UPF and non-UPF conditions based upon relevant dietary factors. Menus were evaluated for palatability and costs, and the commercial additive content of study diets was quantified to explore potential links with outcomes.

RESULTS

Overall diet palatability ratings were similar (UPF = 7.6 ± 1.0; Non-UPF = 6.8 ± 1.5; Like Moderately = 7, Like Very Much = 8). Cost analysis (food + labor) of the 2000 kcal menu (7-d average) revealed lower costs for UPF compared to non-UPF diets ($20.97/d and $40.23/d, respectively). Additive exposure assessment of the 2000 kcal UPF diet indicated that soy lecithin (16×/week), citric acid (13×/week), sorbic acid (13×/week), and sodium citrate (12×/week) were the most frequently consumed additives.

CONCLUSIONS

Whether UPF consumption impairs glucose homeostasis in mid-life adults is unknown. Findings will address this research gap and contribute information on how UPF consumption may influence T2D development.

The Impact of Weight Bias and Stigma on the 24 h Dietary Recall Process in Adults with Overweight and Obesity: A Pilot Study

People with overweight and obesity tend to both underreport dietary energy intake and experience weight stigma. This exploratory pilot study aimed to determine the relationship between weight bias and weight stigma and energy intake reporting accuracy. Thirty-nine weight-stable adults with BMI ≥ 25 completed three 24 h dietary recalls; indirect calorimetry to measure resting metabolic rate; a survey measuring weight stigma, psychosocial constructs, and physical activity; and a semi-structured qualitative interview. Multiple linear regression was used to determine if weight bias internalization, weight bias toward others, and experiences of weight stigma were predictive of the accuracy of energy reporting. A thematic analysis was conducted for the qualitative interviews. Weight stigma was reported by 64.1% of the sample. Weight stigma constructs did not predict the accuracy of energy intake reporting. People with obesity underreported by a mean of 477 kcals (p = 0.02). People classified as overweight overreported by a mean of 144 kcals, but this was not significant (p = 0.18). Participants reported a desire to report accurate data despite concerns about reporting socially undesirable foods. Future research should quantify the impact of weight stigma on energy reporting in 24 h recalls using a larger, more diverse sample size and objective measures like doubly labeled water for validation.

The influence of ultra-processed food consumption on reward processing and energy intake: Background, design, and methods of a controlled feeding trial in adolescents and young adults

BACKGROUND

The greatest age-related weight gain occurs in the early/mid-20s. Overall dietary quality among adolescents and emerging adults (age 18-25) is poor, with ultra-processed foods (UPF) representing more than two-thirds of adolescents' total energy intake (i.e., 68%). UPF consumption may impact cognitive and neurobiological factors that influence dietary decision-making and energy intake (EI). To date, no research has addressed this in this population.

METHODS

Participants aged 18-25 will undergo two 14-day controlled feeding periods (81% UPF, 0% UPF) using a randomly assigned crossover design, with a 4-week washout between conditions. Brain response to a UPF-rich milkshake, as well as behavioral measures of executive function, will be evaluated before and after each diet. Following each diet, measurements include ad libitum buffet meal EI, food selection, eating rate, and eating in the absence of hunger (EAH). Prior to initiating recruitment, controlled diet menus, buffet, and EAH snacks were developed and evaluated for palatability. Sensory and texture attributes of buffet and EAH snack foods were also evaluated.

RESULTS

Overall diet palatability was rated "like very much" (8)/"like moderately"(7) (UPF: 7.6 ± 1.0; Non-UPF: 6.8 ± 1.5). Subjective hardness rating (range = 1-9 [1 = soft, 9 = hard] was similar between UPF and Non-UPF buffet and snack items (UPF:4.22 ± 2.19, Non-UPF: 4.70 ± 2.03), as was the objective measure of hardness (UPF: 2874.33 ± 2497.06 g, Non-UPF: 2243.32 ± 1700.51 g).

CONCLUSIONS

Findings could contribute to an emerging neurobiological understanding of the effects of UPF consumption including energy overconsumption and weight gain among individuals at a critical developmental stage.

Multisectoral Strategies Needed to Establish Healthy Portion Size Norms That Disincentivize Hyperpalatable, Energy-Dense Foods and Sugary Beverages in Food Environments Linked to Obesity and Diet-Related Chronic Diseases in the United States

Over 40 y, Americans have consumed larger portions of hyperpalatable, energy-dense foods, sugary beverages, and meals prepared at home and away from home, which have contributed to obesity and diet-related chronic diseases in the United States (US). This perspective article explores synergies between the portion size and food matrix effects, and their associated biological, physiological, environmental, and cultural susceptibilities for populations. Thereafter, we describe evidence of US public- and private-sector initiatives to reduce, standardize, and incentivize portion size norms to align with recommended servings to promote a healthy weight for children, adolescents, and adults. Practitioners could use the Individual plus Policy, System, and Environment (I + PSE) Framework to implement multisectoral strategies for the US government, businesses, and civil society organizations to establish healthy portion size norms aligned with servings recommended by the Dietary Guidelines for Americans 2020-2025, and to disincentivize overconsumption of hyperpalatable products to reduce obesity and chronic disease risks.

A randomized controlled trial to test the effectiveness of two technology-enhanced diabetes prevention programs in primary care: The DiaBEAT-it study

Objective

To evaluate the effectiveness of two technology-enhanced interventions for diabetes prevention among adults at risk for developing diabetes in a primary care setting.

Methods

The DiaBEAT-it study employed a hybrid 2-group preference (Choice) and 3-group randomized controlled (RCT) design. This paper presents weight related primary outcomes of the RCT arm. Patients from Southwest Virginia were identified through the Carilion Clinic electronic health records. Eligible participants (18 and older, BMI ≥ 25, no Type 2 Diabetes) were randomized to either Choice (n = 264) or RCT (n = 334). RCT individuals were further randomized to one of three groups: (1) a 2-h small group class to help patients develop a personal action plan to prevent diabetes (SC, n = 117); (2) a 2-h small group class plus automated telephone calls using an interactive voice response system (IVR) to help participants initiate weight loss through a healthful diet and regular physical activity (Class/IVR, n = 110); or (3) a DVD with same content as the class plus the same IVR calls over a period of 12 months (DVD/IVR, n = 107).

Results

Of the 334 participants that were randomized, 232 (69%) had study measured weights at 6 months, 221 (66%) at 12 months, and 208 (62%) at 18 months. Class/IVR participants were less likely to complete weight measures than SC or DVD/IVR. Intention to treat analyses, controlling for gender, race, age and baseline BMI, showed that DVD/IVR and Class/IVR led to reductions in BMI at 6 (DVD/IVR -0.94, p < 0.001; Class/IVR -0.70, p < 0.01), 12 (DVD/IVR -0.88, p < 0.001; Class/IVR-0.82, p < 0.001) and 18 (DVD/IVR -0.78, p < 0.001; Class/IVR -0.58, p < 0.01) months. All three groups showed a significant number of participants losing at least 5% of their body weight at 12 months (DVD/IVR 26.87%; Class/IVR 21.62%; SC 16.85%). When comparing groups, DVD/IVR were significantly more likely to decrease BMI at 6 months (p < 0.05) and maintain the reduction at 18 months (p < 0.05) when compared to SC. There were no differences between the other groups.

Conclusions

The DiaBEAT-it interventions show promise in responding to the need for scalable, effective methods to manage obesity and prevent diabetes in primary care settings that do not over burden primary care clinics and providers.

Registration

https://clinicaltrials.gov/ct2/show/NCT02162901, identifier: NCT02162901.

Current Knowledge Base of Beverage Health Impacts, Trends, and Intake Recommendations for Children and Adolescents: Implications for Public Health

PURPOSE OF REVIEW

Improving beverage patterns is important for promoting the health of children and adolescents. Food preferences can begin developing at a young age; thus, children and adolescents should be provided healthy beverages in accordance with current recommendations. The purpose of this review is to identify and summarize existing beverage recommendations for children and adolescents. This review also discusses the health impacts of beverages and how beverage consumption has changed among children and adolescents over time.

RECENT FINDINGS

The mean number of calories that children and adolescents are consuming from beverages on a given day has declined in recent years. However, sugar-sweetened beverages (SSB) are the primary source of added sugars in this population. Therefore, SSB consumption remains a concern, and reducing the intake of SSB is still considered a top priority for helping to improve dietary quality. This review uniquely compiles recommendations into one convenient table for the entire age range of 0-19 years and includes recommendations that can be more adequately individualized. Beverage categories where beverage recommendations from authoritative sources are lacking have also been identified. Potential methods that can be implemented to improve beverage patterns and current public policy recommendations have been discussed to provide actionable steps that public health professionals can utilize in practice. The comprehensive table of beverage recommendations could be useful for professionals promoting the health of children and adolescents in research, clinical, and public health settings.

A Single-Carbon Stable Isotope Ratio Model Prediction Equation Can Estimate Self-Reported Added Sugars Intake in an Adult Population Living in Southwest Virginia

The δ13C value of blood is a novel proposed biomarker of added sugars (AS) intake. AS prediction equations using either a single- (δ13C) or dual-isotope model (δ13C and δ15N) were previously developed in an adult population with high AS intake living in southwest Virginia (reference group). The purpose of this investigation was to test the δ13C single- and δ13C and δ15N dual-isotope prediction equations for AS intake in adults with a lower mean AS intake and different demographic characteristics (test group). The blood samples for the reference (n = 257 for single-isotope, n = 115 for dual-isotope) and test groups (n = 56) were analyzed for δ13C and δ15N values using natural abundance stable isotope mass spectrometry and were compared to reported dietary AS intake. When the δ13C single-isotope equation was applied to the test group, predicted AS intake was not significantly different from reported AS intake (mean difference ± standard error = -3.6 ± 5.5 g, Z = -0.55, p = 0.51). When testing the dual-isotope equation, predicted AS was different from reported AS intake (mean difference ± SEM = 13.0 ± 5.4 g, Z = -2.95, p = 0.003). δ13C value was able to predict AS intake using a blood sample within this population subset. The single-isotope prediction equation may be an alternative method to assess AS intake and is more objective, cost-feasible, and efficient than traditional dietary assessment methods. However, more research is needed to assess this biomarker with rigorous study designs such as controlled feeding.

Prebiotic Inulin Supplementation and Peripheral Insulin Sensitivity in adults at Elevated Risk for Type 2 Diabetes: A Pilot Randomized Controlled Trial

Prediabetes affects 84.1 million adults, and many will progress to type 2 diabetes (T2D). The objective of this proof-of-concept trial was to determine the efficacy of inulin supplementation to improve glucose metabolism and reduce T2D risk. Adults (n = 24; BMI: 31.3 ± 2.9 kg/m²; age: 54.4 ± 8.3 years) at risk for T2D were enrolled in this controlled feeding trial and consumed either inulin (10 g/day) or placebo (maltodextrin, 10 g/day) for six weeks. Assessments included peripheral insulin sensitivity, fasting glucose, and insulin, HOMA-IR, in vivo skeletal muscle substrate preference, Bifidobacteria copy number, intestinal permeability, and endotoxin concentrations. Participant retention was 92%. There were no baseline group differences except for fasting insulin (p = 0.003). The magnitude of reduction in fasting insulin concentrations with inulin (p = 0.003, inulin = Δ-2.9, placebo = Δ2.3) was attenuated after adjustment for baseline concentrations (p = 0.04). After adjusting for baseline values, reduction in HOMA-IR with inulin (inulin = Δ-0.40, placebo=Δ0.27; p = 0.004) remained significant. Bifidobacteria 16s increased (p = 0.04; inulin = Δ3.1e⁹, placebo = Δ-8.9e⁸) with inulin supplementation. Despite increases in gut Bifidobacteria, inulin supplementation did not improve peripheral insulin sensitivity. These findings question the need for larger investigations of inulin and insulin sensitivity in this population.

Preliminary assessment of the Healthy Beverage Index for U.S. Children and Adolescents: a tool to quantify the overall beverage intake quality of 2- to 19-year-olds

BACKGROUND

Improving beverage patterns of children and adolescents is recommended for combatting obesity and reducing disease risk. Therefore, it is important to assess beverage intake quality in this population. For adults, the Healthy Beverage Index (HBI) was created to assess beverage intake quality, but a similar tool did not exist for children and adolescents.

OBJECTIVE

The objective was to develop an HBI for U.S. Children and Adolescents (HBI-CA), and then assess the validity and reliability of this tool.

DESIGN

Modeled after the adult HBI, age-specific, evidence-based beverage recommendations were compiled. Ten components were included to assess beverage intake quality. Validity and reliability were assessed using cross-sectional data and methods similar to those used for the evaluation of the Healthy Eating Index.

PARTICIPANTS

The 2015-2016 National Health and Nutrition Examination Survey provided 24-hour dietary recall data for 2,874 children and adolescents aged 2-19 years.

MAIN OUTCOME MEASURES

HBI-CA scores were the main outcome measure.

STATISTICAL ANALYSES PERFORMED

To assess validity, independent t-tests were used to determine differences in HBI-CA component and total scores among groups, and principal component analysis (PCA) was completed to examine multidimensionality of the HBI-CA. Pearson's bivariate correlations were used to assess reliability.

RESULTS

The HBI-CA produced a (mean±standard error) total score of 69.2±0.8, which is similar to the adult HBI mean total score of 63. PCA identified six factors, indicating the multidimensionality of the HBI-CA, with more than one combination of components contributing to variation in total scores. Most HBI-CA components were significantly correlated to the total score, with met fluid requirements, total beverage energy, sugar-sweetened beverage, and water components demonstrating the strongest correlations (r ranged 0.335-0.735, P-value ≤0.01).

CONCLUSIONS

The results provide preliminary evidence to support the validity and reliability of the HBI-CA. If future research establishes the predictive validity and sensitivity of the HBI-CA, this tool could be useful to quantify the beverage intake quality of children and adolescents.

Fasting and postprandial trimethylamine N-oxide in sedentary and endurance-trained males following a short-term high-fat diet

Gut bacteria release trimethylamine (TMA) from dietary substrates. TMA is absorbed and is subsequently oxidized in the liver to produce trimethylamine N-oxide (TMAO). Plasma TMAO levels are positively correlated with risk for type 2 diabetes (T2D) and cardiovascular disease (CVD). High-fat diet (HFD) consumption has been reported to increase fasting and postprandial TMAO in sedentary individuals. However, whether the increase in TMAO with consumption of an HFD is observed in endurance-trained males is unknown. Healthy, sedentary (n = 17), and endurance-trained (n = 7) males consumed a 10-day eucaloric diet comprised of 55% carbohydrate, 30% total fat, and <10% saturated fat prior to baseline testing. Blood samples were obtained in a fasted state and for a 4-hour high-fat challenge (HFC) meal at baseline and then again following 5-day HFD (30% carbohydrate, 55% total fat, and 25% saturated fat). Plasma TMAO and TMA-moiety (choline, betaine, L-carnitine) concentrations were measured using isocratic ultraperformance liquid chromatography-tandem mass spectrometry. Age (23 ±3 vs. 22 ± 2 years) and body mass index (23.0 ± 3.0 vs. 23.5 ± 2.1 kg/m2 ) were similar (both p > 0.05) in the sedentary and endurance-trained group, respectively. VO2max was significantly higher in the endurance-trained compared with sedentary males (56.7 ± 8.2 vs. 39.9 ± 6.0 ml/kg/min). Neither the HFC nor the HFD evoked a detectable change in plasma TMAO (p > 0.05) in either group. Future studies are needed to identify the effects of endurance training on TMAO production.

The Validity of Urine Color as a Hydration Biomarker within the General Adult Population and Athletes: A Systematic Review

Frequent monitoring of hydration status may help to avoid the adverse effects of dehydration. Other than urine color assessment, hydration assessment methods are largely impractical for the general population and athletes to implement on a routine basis. Despite its widespread use, the validity of urine color as an indicator of hydration status has not been systematically evaluated. The objective of this systematic review is to determine the validity of urine color evaluation as a hydration status assessment method in the general adult population, older adults, and athletes. Using the PRISMA guidelines, electronic databases were searched to identify original research articles of all study design types for inclusion. Of the 424 articles screened, 10 met inclusion criteria. Most studies compared urine color to either urinary specific gravity or urine osmolality, and reported significant associations (r) ranging from 0.40 to 0.93. Lower correlations were noted in studies of adults aged >60 years. Studies generally reported a high sensitivity of urine color as a diagnostic tool for detecting dehydration and supported the ability of this method to distinguish across categories of hydration status. Research is needed to determine if clinicians, patients, and clients can accurately utilize this method in clinical and real-world settings. Future research is also needed to extend these findings to other populations, such as children.Key teaching pointsInadequate hydration can lead to impairments in physical performance and cognitive function.Methods used to assess hydration status include plasma/serum osmolality, urinary specific gravity (USG), urine osmolality (Uosm), change in body weight, urine volume, and urine color.Urine color assessment is a practical method that is routinely used in clinical, athletic, and other settings. The validity of this method has not been systemically evaluated.Available research was limited to 10 articles.Validity of this method was generally supported; however, research has not investigated the validity of this method by clinicians, patients and clients.

Update of the BEVQ-15, a beverage intake questionnaire for habitual beverage intake for adults: determining comparative validity and reproducibility

INTRODUCTION

The BEVQ-15 is a beverage intake questionnaire that estimates the habitual average daily intake of 15 beverage categories (kcal and fl oz), as well as total sugar-sweetened beverages (SSB) and total beverages. However, subsequent to its initial validation in 2010, it has not been updated. The present study aimed to assess the convergent validity and reproducibility of the updated form of the BEVQ-15 to better reflect current beverage consumption trends.

METHODS

The study population included adults (n = 50) aged ≥18 years, recruited from a local university community. Participation consisted of three laboratory visits within a 4-week period in which the updated BEVQ-15 was administered during the first and last visit and four 24-h dietary recalls were collected. BEVQ-15 modifications included removing limits of 60 fl oz per beverage, adding a nut milk category, and providing creamer and sweetener preferences for coffee/tea categories. Convergent validity was assessed by comparing reported beverage intake between the BEVQ-15 and dietary recalls. Reproducibility was assessed by comparing both BEVQ-15 administrations. Analyses included descriptive statistics, Wilcoxon signed rank tests, Bland-Altman plots and Spearman's correlations.

RESULTS

For validity, Bland-Altman plot agreement between the BEVQ-15 and recalls was in the range 92-96% for total SSB and total beverage intake. For reproducibility, all beverage categories, total SSB, and total beverage intake were significantly correlated between the two BEVQ-15 administrations (r = 0.41-0.85; P ≤ 0.01).

CONCLUSIONS

This updated version of the BEVQ-15 demonstrated moderate convergent validity and reproducibility for total beverage consumption among well-educated southwest Virginia adults.

Postprandial skeletal muscle metabolism following a high-fat diet in sedentary and endurance-trained males

Our objective was to determine the influence of a high-fat diet (HFD) on fasting and postprandial skeletal muscle substrate metabolism in endurance-trained (ET) compared with sedentary (SED) humans. SED (n = 17) and ET (n = 7) males were control-fed a 10-day moderate-fat diet followed by a 5-day isocaloric HFD (55% fat, 30% carbohydrate). Skeletal muscle biopsies were taken in the fasted condition and 4 h after a high-fat meal (820 kcals; 63% fat and 25% carbohydrate). Palmitate-induced suppression of pyruvate oxidation, an indication of substrate preference, and oxidation of fat and glucose were measured in homogenized skeletal muscle in fasted and fed states. Postprandial responses were calculated as percent changes from fasting to fed states. Postprandial suppression of pyruvate oxidation was maintained after the HFD in ET, but not SED skeletal muscle, suggesting greater adaptability to dietary intake changes in the former. Fasting total fat oxidation increased due to the HFD in ET skeletal muscle (P = 0.006), which was driven by incomplete fat oxidation (P = 0.008). Fasting fat oxidation remained unchanged in skeletal muscle of SED individuals. Yet, postprandial fat oxidation was similar between groups. Fasting glucose oxidation was elevated after the HFD in ET (P = 0.036), but not SED, skeletal muscle. Postprandial glucose oxidation was reduced due to the HFD in SED (P = 0.002), but not ET, skeletal muscle. These findings provide insight into differing substrate metabolism responses between SED and ET individuals and highlight the role that the prevailing diet may play in modulating fasting and postprandial metabolic responses in skeletal muscle.NEW & NOTEWORTHY The relationship between high dietary fat intake and physical activity level and their combined effect on skeletal muscle substrate metabolism remains unclear. We assessed the influence of the prevailing diet in modulating substrate oxidation in skeletal muscle of endurance-trained compared with sedentary humans during a high-fat challenge meal. Collectively, our findings demonstrate the adaptability of skeletal muscle in endurance-trained individuals to high dietary fat intake.

Serum endotoxin, gut permeability and skeletal muscle metabolic adaptations following a short term high fat diet in humans

BACKGROUND

Our previous work demonstrated that a short-term high fat diet (HFD) increased fasting serum endotoxin, altered postprandial excursions of serum endotoxin, and led to metabolic and transcriptional responses in skeletal muscle in young, healthy male humans.

PURPOSE

The purpose of the present study was to determine if a short-term high fat diet: 1) increases intestinal permeability and, in turn, fasting endotoxin concentrations and 2) decreases postprandial skeletal muscle fat oxidation.

METHODS

Thirteen normal weight young adult males (BMI 23.1 ± 0.8 kg/m², age 22.2 ± 0.4 years) were fed a control diet (55% carbohydrate, 30% fat, 9% of which was saturated, 15% protein) for two weeks, followed by 5 days of an isocaloric HFD (30% carbohydrate, 55% fat, 25% of which was saturated, 15% protein, isocaloric to the control diet). Intestinal permeability (via four sugar probe test) was assessed in the fasting state. Both before and after the HFD, a high fat meal challenge (HFM, 820 kcal, 25% carbohydrate, 63% fat, 26% of which was saturated, and 12% protein) was administered. After an overnight fast, blood samples were collected before and every hour for 4 h after the HFM to assess endotoxin, and other serum blood measures. Muscle biopsies were obtained from the vastus lateralis before and 4 h after the HFM in order to assess substrate oxidation (glucose, fatty acid and pyruvate) using radiolabeled techniques. Insulin sensitivity was assessed via intravenous glucose tolerance test. Intestinal permeability, blood samples and muscle biopsies were assessed in the same manner before and following the HFD.

MAIN FINDINGS

Intestinal permeability was not affected by HFD (p > 0.05), but fasting endotoxin increased two fold following the HFD (p = 0.04). Glucose oxidation and fatty acid oxidation in skeletal muscle homogenates significantly increased after the HFM before the HFD (+97%, and +106% respectively) but declined after the HFM following 5 days of the HFD (-24% and +16% respectively). Fatty acid suppressibility of pyruvate oxidation increased significantly after the HFM (+32%) but this physiological effect was abolished following 5 days of the HFD (+7%). Insulin sensitivity did not change following the HFD.

CONCLUSION

These findings demonstrate that in healthy young men, consuming an isocaloric HFD for 5 days increases fasting endotoxin, independent of changes in gut permeability. These changes in endotoxin are accompanied by a broad effect on skeletal muscle substrate metabolism including increases in postprandial fat oxidation. Importantly, the latter occurs independent of changes in body weight and whole-body insulin sensitivity.

Advances in Nutrition Science and Integrative Physiology: Insights From Controlled Feeding Studies

Nutrition science is a highly impactful but contentious area of biomedical science. Establishing cause and effect relationships between the nutrients and/or diets we consume and the avoidance of or risk of disease is extremely challenging. As such, evidence-based nutrition is best served by considering the totality of evidence across multiple study types including nutritional epidemiological studies, randomized controlled trials of behavioral interventions, and controlled feeding studies. The purpose of the present review is to provide an overview for those conducting research outside of clinical nutrition on how controlled feeding studies can be used to gain insight into integrative physiology/metabolism as well as to inform dietary guidelines. We discuss the rationale, basic elements, and complexities of conducting controlled feeding studies and provide examples of contributions of controlled feeding studies to advances in nutrition science and integrative physiology. Our goal is to provide a resource for those wishing to leverage the experimental advantage provided by controlled feeding studies in their own research programs.

Short-term changes in added sugar consumption by adolescents reflected in the carbon isotope ratio of fingerstick blood

BACKGROUND

Consumption of added sugars (AS) and sugar-sweetened beverages (SSB) may adversely affect adolescents' weight and cardiovascular disease risk. Reliance on self-reported dietary assessment methods is a common research limitation, which could be overcome by dietary intake biomarkers.

AIM

The investigation was a proof-of-concept study to evaluate the proposed carbon isotope ratio (δ¹³C) biomarker of AS intake in adolescents, using a controlled feeding design.

METHODS

Participants (n = 33, age 15.3 years, 53% female) underwent two seven-day controlled feeding periods in a randomly assigned order. Diets were matched in composition except for AS content (5% or 25% of total energy). Fasting fingerstick blood samples were collected daily during each diet period.

RESULTS

Fingerstick δ¹³C values changed from day 1 to 8 by -0.05 ± 0.071‰ on 5% AS, and +0.03 ± 0.083‰ on 25% AS (p ≤ 0.001). Reliability was demonstrated between day 7 and 8 δ¹³C values on the 5% (ICC = 0.996, p ≤ 0.001) and 25% (ICC = 0.997, p ≤ 0.001) AS diets.

CONCLUSIONS

Larger scale investigations are warranted to determine if this technique could be applied to population-level research in order to help assess the effectiveness of interventions aimed at reducing the consumption of AS or SSB intake.

Supporting maintenance of sugar-sweetened beverage reduction using automated versus live telephone support: findings from a randomized control trial

Background

Although reducing sugar-sweetened beverage (SSB) intake is an important behavioral strategy to improve health, no known SSB-focused behavioral trial has examined maintenance of SSB behaviors after an initial reduction. Guided by the RE-AIM framework, this study examines 6–18 month and 0–18 month individual-level maintenance outcomes from an SSB reduction trial conducted in a medically-underserved, rural Appalachia region of Virginia. Reach and implementation indicators are also reported.

Methods

Following completion of a 6-month, multi-component, behavioral RCT to reduce SSB intake (SIPsmartER condition vs. comparison condition), participants were further randomized to one of three 12-month maintenance conditions. Each condition included monthly telephone calls, but varied in mode and content: 1) interactive voice response (IVR) behavior support, 2) human-delivered behavior support, or 3) IVR control condition. Assessments included the Beverage Intake Questionnaire (BEVQ-15), weight, BMI, and quality of life. Call completion rates and costs were tracked. Analysis included descriptive statistics and multilevel mixed-effects linear regression models using intent-to-treat procedures.

Results

Of 301 subjects enrolled in the 6-month RCT, 242 (80%) were randomized into the maintenance phase and 235 (78%) included in the analyses. SIPsmartER participants maintained significant 0–18 month decreases in SSB. For SSB, weight, BMI and quality of life, there were no significant 6–18 month changes among SIPsmartER participants, indicating post-program maintenance. The IVR-behavior participants reported greater reductions in SSB kcals/day during the 6–18 month maintenance phase, compared to the IVR control participants (− 98 SSB kcals/day, 95% CI = − 196, − 0.55, p < 0.05); yet the human-delivered behavior condition was not significantly different from either the IVR-behavior condition (27 SSB kcals/day, 95% CI = − 69, 125) or IVR control condition (− 70 SSB kcals/day, 95% CI = − 209, 64). Call completion rates were similar across maintenance conditions (4.2–4.6 out of 11 calls); however, loss to follow-up was greatest in the IVR control condition. Approximated costs of IVR and human-delivered calls were remarkably similar (i.e., $3.15/participant/month or $38/participant total for the 12-month maintenance phase), yet implications for scalability and sustainability differ.

Conclusion

Overall, SIPsmartER participants maintained improvements in SSB behaviors. Using IVR to support SSB behaviors is effective and may offer advantages as a scalable maintenance strategy for real-world systems in rural regions to address excessive SSB consumption.

Trial registry

Clinicaltrials.gov; NCT02193009; Registered 11 July 2014. Retrospectively registered.

Adolescents perceive a low added sugar adequate fiber diet to be more satiating and equally palatable compared to a high added sugar low fiber diet in a randomized-crossover design controlled feeding pilot trial

BACKGROUND

High added sugar (AS) intake is associated with obesity and poor diet quality. Guidelines recommended limiting AS to 5-10% of total energy intake, but palatability and feasibility of this AS intake level is uncertain.

OBJECTIVE

To compare adolescents' perceptions of hunger, fullness, and palatability in response to a low AS adequate fiber (LASAF; 5% total energy from AS and 13.5 g fiber/1000 kcal) and a high AS low fiber (HASLF; 25% total energy form AS and 8.2 g/1000 kcal) diet.

DESIGN

Adolescents (n = 32, age: 15.3 ± 1.6 yrs., BMI percentile: 47 ± 4, 15 male) completed a randomized, crossover, controlled feeding study. Participants consumed calorie-matched LASAF and HASLF diets for 7 days, separated by a 4 week washout. Body weight was monitored daily on each diet. Hunger, fullness, and palatability were assessed via 100 mm visual analogue scales at the end of each feeding period. Differences were assessed with paired sample t-tests. Data are expressed as mean ± SD.

RESULTS

Participants remained weight stable, and no difference in weight change between diet conditions was detected (LASAF: -0.06 ± 0.7 vs. HASLF: -0.02 ± 0.6 kg, p = 0.751). Less hunger (LASAF: 24.1 ± 14.6 vs. HASLF: 32.1 ± 17.6 mm, p = 0.024) and greater fullness (LASAF: 70.2 ± 12.3 vs. HASLF: 61.3 ± 18.1 mm, p = 0.006) were reported on the LASAF compared to the HASLF. Participants reported the diets to be equally palatable (LASAF: 39.6 ± 12.9 vs. HASLF: 37.2 ± 17.8 mm, p = 0.440).

CONCLUSIONS

Adolescents perceive a LASAF diet to be as palatable as a HASLF diet, but more satiating. LASAF diets should be investigated as a strategy for weight control in adolescents.

The δ13C Value of Fingerstick Blood Is a Valid, Reliable, and Sensitive Biomarker of Sugar-Sweetened Beverage Intake in Children and Adolescents

Background

Reliance on self-reported dietary intake methods is a commonly cited research limitation, and dietary misreporting is a particular problem in children and adolescents. Objective indicators of dietary intake, such as dietary biomarkers, are needed to overcome this research limitation. The added sugar (AS) biomarker δ13C, which measures the relative abundance of 13C to 12C, has demonstrated preliminary validity in adults.

Objective

The purpose of this investigation was to determine the comparative validity, test-retest reliability, and sensitivity of the δ13C biomarker to detect AS and sugar-sweetened beverage (SSB) intake using fingerstick blood samples in children and adolescents.

Methods

Children (aged 6-11 y, n = 126, 56% male, mean ± SD age: 9 ± 2 y) and adolescents (aged 12-18 y, n = 200, 44% male, mean ± SD age: 15 ± 2 y) completed 4 testing sessions within a 3-wk period. Participants' height, weight, demographic characteristics, and health history were determined at the first session; 24-h recalls were obtained at each visit and fingerstick blood samples were collected at visits 1 and 3. Samples were analyzed for δ13C value using natural abundance stable isotope mass spectrometry. δ13C value was compared with dietary outcomes in the full sample, and in child and adolescent subgroups. t Tests and correlational analyses were used to assess biomarker validity and reliability, whereas logistic regression and area under the receiver-operator characteristic curve (AUC) were used to evaluate sensitivity.

Results

Reported mean ± SD AS consumption was 82.2 ± 35.8 g/d and 329 ± 143 kcal/d, and SSB consumption was 222 ± 243 mL/d and 98 ± 103 kcal/d. Mean δ13C value was -19.65 ± 0.69‰, and was lower in children than in adolescents (-19.80 ± 0.67‰ compared with -19.56 ± 0.67‰, P = 0.002). δ13C values were similar across sessions (visit 1: -19.66 ± 0.68‰; visit 3: -19.64 ± 0.68‰; r = 0.99, P < 0.001) and were associated (P < 0.001) with intake of total AS (grams, kilocalories: r = 0.29) and SSB (milliliters, kilocalories: r = 0.35). The biomarker was able to better discriminate between high and low SSB consumers than high and low AS consumers, as demonstrated by the AUC (0.75 and 0.62, respectively).

Conclusions

The δ13C biomarker is a promising, minimally invasive, objective biomarker of SSB intake in children and adolescents. Further evaluation using controlled feeding designs is warranted. Registered at clinicaltrials.gov as NCT02455388.

Size and mineral composition of airborne particles generated by an ultrasonic humidifier

This study describes the size distribution and concentration of particles expelled by a portable, 3-L ultrasonic humidifier. The ultrasonic humidifier was filled with waters of varying mineral content and hardness. Aerosol size distributions were measured during 8 hours of humidifier operation in a typical bedroom. Humidifiers produced approximately 1.22 × 10¹⁰ -2.50 × 10¹⁰ airborne particles per milliliter of water consumed, resulting in airborne particle concentrations of 3.01-5.91 × 10⁴  #/cm³ , with modes ranging between 109 and 322 nm in diameter. The emission rate of particles varied by water type from 1.02 × 10⁹ to 2.27 × 10⁹  #/s. Lower mineral waters produced fewer, smaller particles when compared to higher mineral waters. Chemical analyses of particles collected with a cascade impactor indicated that the minerals in emitted particles had the same relative mineral concentrations as the fill water. Our results demonstrate that ultrasonic humidifiers should be considered a source of inhalation exposure to minerals dissolved in water, and that the magnitude of exposure to inhalable particles will vary with water quality.

Urinary Excretion of Sodium, Nitrogen, and Sugar Amounts Are Valid Biomarkers of Dietary Sodium, Protein, and High Sugar Intake in Nonobese Adolescents

Background: Objective indicators of dietary intake (e.g., biomarkers) are needed to overcome the limitations of self-reported dietary intake assessment methods in adolescents. To our knowledge, no controlled feeding studies to date have evaluated the validity of urinary sodium, nitrogen, or sugar excretion as dietary biomarkers in adolescents.Objective: This investigation aimed to evaluate the validity of urinary sodium, nitrogen, and total sugars (TS) excretion as biomarkers for sodium, protein, and added sugars (AS) intake in nonobese adolescents.Methods: In a crossover controlled feeding study design, 33 adolescents [12-18 y of age, 47 ± 25th percentile (mean ± SD) of body mass index (BMI; in kg/m²) for age] consumed 5% AS [low added sugars (LAS)] and 25% AS [high added sugars (HAS)] isocaloric, macronutrient-matched (55% carbohydrate, 30% fat, and 15% protein) diets for 7 d each, in a randomly assigned order, with a 4-wk washout period between diets. On the final 2 d of each diet period, 24-h urine samples were collected. Thirty-two adolescents completed all measurements (97% retention).Results: Urinary sodium was not different from the expected 90% recovery (mean ± SD: 88% ± 18%, P = 0.50). Urinary nitrogen was correlated with protein intake (r = 0.69, P < 0.001), although it was below the 80% expected recovery (62% ± 7%, P < 0.001). Urinary TS values were correlated with AS intake during the HAS diet (r = 0.77, P < 0.001) and had a higher R² value of 0.28 than did AS intake (R² = 0.36). TS excretion differed between LAS (0.226 ± 0.09 mg/d) and HAS (0.365 ± 0.16 mg/d) feeding periods (P < 0.001).Conclusions: Urinary sodium appears to be a valid biomarker for sodium intake in nonobese adolescents. Urinary nitrogen is associated with protein intake, but nitrogen excretion rates were less than previously reported for adults, possibly owing to adolescent growth rates. TS excretion reflects AS at 25% AS intake and was responsive to the change in AS intake. Thus, urinary biomarkers are promising objective indicators of dietary intake in adolescents, although larger-scale feeding trials are needed to confirm these findings. This trial was registered at clinicaltrials.gov as NCT02455388.

Skeletal muscle autophagy and mitophagy in endurance-trained runners before and after a high-fat meal

Objective

We tested the hypothesis that skeletal muscle of endurance-trained male runners would exhibit elevated autophagy and mitophagy markers, which would be associated with greater metabolic flexibility following a high-fat meal (HFM).

Methods

Muscle biopsies were collected to determine differences in autophagy and mitophagy protein markers and metabolic flexibility under fasting conditions and 4 h following a HFM between endurance-trained male runners (n = 10) and sedentary, non-obese controls (n = 9).

Results

Maximal oxygen consumption (ml·kg·min⁻¹) was approximately 50% higher (p < 0.05) in endurance-trained runners compared with sedentary controls (65.8 ± 2.3 and 43.1 ± 3.4, respectively). Autophagy markers were similar between groups. Mitophagy and mitochondrial dynamics protein markers were significantly higher in skeletal muscle of endurance-trained runners compared with sedentary controls in the fasted state, although unaffected by the HFM. Skeletal muscle metabolic flexibility was similar between groups when fasted (p > 0.05), but increased in response to the HFM in endurance-trained athletes only (p < 0.005). Key mitophagy markers, phospho-Pink1^Thr257 and phospho-Parkin^S65 (r = 0.64, p < 0.005), and phospo-Parkin^Ser65 and phospho-Drp1^Ser616 (r = 0.70, p < 0.05) were correlated only within the endurance-trained group. Autophagy and mitophagy markers were not correlated with metabolic flexibility.

Conclusion

In summary, mitophagy may be enhanced in endurance-trained runners based on elevated markers of mitophagy and mitochondrial dynamics. The HFM did not alter autophagy or mitophagy in either group. The absence of a relationship between mitophagy markers and metabolic flexibility suggests that mitophagy is not a key determinant of metabolic flexibility in a healthy population, but further investigation is warranted.

•

Basal autophagy is similar in skeletal muscle of endurance-trained and sedentary males.

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Trained and sedentary skeletal muscle autophagy is unaltered following high-fat meal.

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Mitophagy activity is greater in endurance-trained than sedentary skeletal muscle.

•

Greater mitophagy is related to increased metabolic flexibility after high-fat meal.

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Trained and sedentary skeletal muscle mitophagy is unaltered following high-fat meal.

Pre-meal inulin consumption does not affect acute energy intake in overweight and obese middle-aged and older adults: A randomized controlled crossover pilot trial

BACKGROUND

Three-fourths of adults older than 55 years in the United States are overweight or obese. Prebiotics including inulin-type fructans may benefit with weight management.

AIM

We aimed to investigate the acute effects of pre-meal inulin consumption on energy intake (EI) and appetite in older adults.

METHODS

Sedentary, overweight or obese middle-aged and older adults ( n = 7, 60.9 ± 4.4 years, BMI 32.9 ± 4.3 kg/m²) ingested inulin (10 g) or a water preload before each test period in a randomly assigned order. EI, appetite and gastrointestinal symptoms were monitored during the following 24 h.

RESULTS

No differences in EI were noted between conditions (inulin: 14744 ± 5552 kJ, control: 13924 ± 4904 kJ, p > 0.05). Rumbling was increased with inulin consumption ( p < 0.05).

CONCLUSION

Pre-meal inulin consumption does not acutely decrease EI or suppress appetite in older adults. Further research should address individual differences among diets, eating behaviors, and microbiota profiles.

Resistance training is associated with spontaneous changes in aerobic physical activity but not overall diet quality in adults with prediabetes

BACKGROUND

Aerobic exercise interventions have been shown to result in alterations to dietary intake and non-exercise physical activity (PA). To date, the ability for resistance training (RT) to influence other health-related behaviors has not been examined. This study aimed to determine if initiation and maintenance of RT is associated with spontaneous changes in dietary quality and non-RT PA in adults with prediabetes.

METHODS

Overweight/obese adults (n=170, BMI=32.9±3.8kg·m², age=59.5±5.5years, 73% female) with prediabetes were enrolled in the 15-month Resist Diabetes trial. Participants completed a supervised 3-month RT initiation phase followed by a 6-month maintenance phase and a 6-month no-contact phase. Participants were not encouraged to change eating or non-RT PA behaviors. At baseline, and months 3, 9, and 15, three 24-hour diet recalls were collected to evaluate dietary intake and quality, the Aerobics Institute Longitudinal Study Questionnaire was completed to evaluate non-RT PA, and body mass, body composition (DXA), and muscular strength were measured. At months 3, 9, and 15 social cognitive theory (SCT) constructs were assessed with a RT Health Beliefs Questionnaire. Mixed effects models were used to assess changes in dietary intake and non-RT PA over the 15-month study period.

RESULTS

Energy and carbohydrate intake decreased with RT initiation and maintenance phases (baseline to month 9: β=-87.9, p=0.015 and β=-16.3, p<0.001, respectively). No change in overall dietary quality (Healthy Eating Index [HEI]-2010 score: β=-0.13, p=0.722) occurred, but alterations in HEI-2010 sub-scores were detected. Maintenance of RT was accompanied by an increase in MET-min/week of total non-RT PA (month 3 to month 9: β=146.2, p=0.01), which was predicted by increased self-regulation and decreased negative outcome expectancies for RT (β=83.7, p=0.014 and β=-70.0, p=0.038, respectively).

CONCLUSIONS

Initiation and maintenance of RT may be a gateway behavior leading to improvements in other health-related behaviors. These results provide rationale for single-component lifestyle interventions as an alternative to multi-component interventions, when resources are limited.

Dietary quality changes in response to a sugar-sweetened beverage-reduction intervention: results from the Talking Health randomized controlled clinical trial

Background: The reduction of sugar-sweetened beverage (SSB) intake may be beneficial for weight management and other related health conditions; however, to our knowledge, no data exist regarding the spontaneous changes in other dietary components or the overall dietary quality after an SSB-reduction intervention.Objectives: We explored longitudinal changes within and between an SSB-reduction intervention (SIPsmartER) and a physical activity intervention (MoveMore) with respect to spontaneous changes in 1) energy intake and macronutrients and micronutrients, 2) dietary quality [Healthy Eating Index-2010 (HEI)], and 3) beverage categories.Design: Participants were enrolled in a 6-mo, community-based behavioral trial and randomly assigned into either the SIPsmartER (n = 149) intervention group or the MoveMore (n = 143) matched-contact comparison group. Dietary intake was assessed through a mean of three 24-h dietary recalls at baseline and 6 mo. Dietary recalls were analyzed with the use of nutritional analysis software. A multilevel, mixed-effects linear regression with intention-to-treat analyses is presented.Results: SIPsmartER participants showed a significant reduction in total SSBs (mean decrease: -366 mL; P ≤ 0.001). Several spontaneous changes occurred within the SIPsmartER group and, compared with the MoveMore group, included significant HEI improvements for empty calorie, total vegetable, and total HEI scores (mean increases: 2.6, 0.3, and 2.6, respectively; all P ≤ 0.01). Additional positive changes were shown, including significant decreases in total energy intake, trans fat, added sugars, and total beverage energy (all P ≤ 0.05). Few dietary changes were noted in the MoveMore group over the 6-mo intervention.Conclusions: Intervention of the single dietary component SSB resulted in additional spontaneous and beneficial dietary changes. Interventions that target a single dietary change, such as limiting SSB intake to <240 mL/d (<8 fl oz/d), may improve the overall dietary quality health and provide motivation to make additional dietary changes. This trial was registered at clinicaltrials.gov as NCT02193009.

Dietary Intake, Body Composition, and Menstrual Cycle Changes during Competition Preparation and Recovery in a Drug-Free Figure Competitor: A Case Study

Physique competitions are events in which competitors are judged on muscular appearance and symmetry. The purpose of this retrospective case study was to describe changes in dietary intake, body mass/composition, and the menstrual cycle during the 20-week competition preparation (PREP) and 20-week post competition recovery (REC) periods of a drug-free amateur female figure competitor (age = 26–27, BMI = 19.5 kg/m²). Dietary intake (via weighed food records) and body mass were assessed daily and averaged weekly. Body composition was estimated via Dual-energy X-ray absorptiometry (DXA) and 7-site skinfold measurements. Energy intake, body mass and composition, and energy availability decreased during the 20-week PREP period (changes of ~298 kcals, 5.1 kg, 6.5% body fat, and 5.4 kcal/kg fat free mass, respectively) and returned to baseline values by end of the 20-week REC period. Menstrual cycle irregularity was reported within the first month of PREP and the last menstruation was reported at week 11 of PREP. Given the potentially adverse health outcomes associated with caloric restriction, future, prospective cohort studies on the physiological response to PREP and REC are warranted in drug-free, female physique competitors.

Resistance exercise training and in vitro skeletal muscle oxidative capacity in older adults

Whether resistance exercise training (RET) improves skeletal muscle substrate oxidative capacity and reduces mitochondrial production of reactive oxygen species in older adults remains unclear. To address this, 19 older males (≥60 years) were randomized to a RET (n = 11) or to a waitlist control group (n = 8) that remained sedentary for 12 weeks. RET was comprised of three upper body and four lower body movements on resistance machines. One set of 8-12 repetitions to failure of each movement was performed on three nonconsecutive days/week. Improvements in chest press and leg press strength were assessed using a three-repetition maximum (3 RM). Body composition was assessed via dual energy X-ray absorptiometry. Muscle biopsies were obtained from the vastus lateralis muscle at baseline and at both 3 weeks and 12 weeks. Palmitate and pyruvate oxidation rates were measured from the (14)CO2 produced from [1-(14)C] palmitic acid and [U-(14)C] pyruvate, respectively, during incubation of muscle homogenates. PGC-1α, TFAM, and PPARδ levels were quantified using qRT-PCR Citrate synthase (CS) and β-HAD activities were determined spectrophotometrically. Mitochondrial production of reactive oxygen species (ROS) were assessed using the Amplex Red Hydrogen Peroxide/Peroxidase assay. There were no significant changes in body weight or body composition following the intervention. Chest press and leg press strength (3RM) increased ~34% (both P < 0.01) with RET There were no significant changes in pyruvate or fatty acid oxidation or in the expression of target genes with the intervention. There was a modest increase (P < 0.05) in βHAD activity with RET at 12 weeks but the change in CS enzyme activity was not significant. In addition, there were no significant changes in ROS production in either group following RET Taken together, the findings of this study suggest that 12 weeks of low volume RET does not increase skeletal muscle oxidative capacity or reduce ROS production in older adults.

Psychosocial mediators of a theory-based resistance training maintenance intervention for prediabetic adults

OBJECTIVE

Examine psychosocial mediators of the effects of high vs. low-dose resistance training (RT) maintenance interventions among older (ages 50-69), overweight and pre-diabetic adults.

DESIGN

Participants (N = 123) completed a three-month supervised RT initiation phase and were subsequently randomised (time 1) to high or low-dose six-month unsupervised RT maintenance interventions (time 2), followed by a six-month no-contact phase (time 3).

MAIN OUTCOME MEASURES

Online measures of putative mediators and RT behaviour.

RESULTS

RT intervention condition (high vs. low dose) had significant effects on change from time 1 to time 2 in behavioural expectation, self-regulation and perceived satisfaction (f(2) = .04-.08), but not outcome expectancies, RT strategies or behavioural intentions (f(2) ≤ .02). Change in each of the putative mediators, except for outcome expectancies (f(2) ≤ .02), had significant effects on RT behaviour at times 2 (f(2) = .12-.27) and 3 (f(2) = .23-.40). In a multiple mediation model, behavioural expectation (f(2) = .11) and self-regulation (f(2) = .06) mediated the effects of RT intervention condition on time 2 RT behaviour, whereas perceived satisfaction did not (f(2) = .01). Self-regulation was a significant mediator of intervention effects on time 3 RT behaviour (f(2) = .11), but behavioural expectation and perceived satisfaction were not (f(2) = .04).

CONCLUSIONS

Findings suggest that behavioural expectation and self-regulation are appropriate targets for RT maintenance interventions among at-risk older adults.

Assessing clarity of message communication for mandated USEPA drinking water quality reports

The United States Environmental Protection Agency mandates that community water systems (CWSs), or drinking water utilities, provide annual consumer confidence reports (CCRs) reporting on water quality, compliance with regulations, source water, and consumer education. While certain report formats are prescribed, there are no criteria ensuring that consumers understand messages in these reports. To assess clarity of message, trained raters evaluated a national sample of 30 CCRs using the Centers for Disease Control Clear Communication Index (Index) indices: (1) Main Message/Call to Action; (2) Language; (3) Information Design; (4) State of the Science; (5) Behavioral Recommendations; (6) Numbers; and (7) Risk. Communication materials are considered qualifying if they achieve a 90% Index score. Overall mean score across CCRs was 50 ± 14% and none scored 90% or higher. CCRs did not differ significantly by water system size. State of the Science (3 ± 15%) and Behavioral Recommendations (77 ± 36%) indices were the lowest and highest, respectively. Only 63% of CCRs explicitly stated if the water was safe to drink according to federal and state standards and regulations. None of the CCRs had passing Index scores, signaling that CWSs are not effectively communicating with their consumers; thus, the Index can serve as an evaluation tool for CCR effectiveness and a guide to improve water quality communications.

Effects of a behavioral and health literacy intervention to reduce sugar-sweetened beverages: a randomized-controlled trial

Background

Despite excessive consumption of sugar-sweetened beverages (SSB), little is known about behavioral interventions to reduce SSB intake among adults, particularly in medically-underserved rural communities. This type 1 effectiveness-implementation hybrid RCT, conducted in 2012–2014, applied the RE-AIM framework and was designed to assess the effectiveness of a behavioral intervention targeting SSB consumption (SIPsmartER) when compared to an intervention targeting physical activity (MoveMore) and to determine if health literacy influenced retention, engagement or outcomes.

Methods

Guided by the Theory of Planned Behavior and health literacy strategies, the 6 month multi-component intervention for both conditions included three small-group classes, one live teach-back call, and 11 interactive voice response calls. Validated measures were used to assess SSB consumption (primary outcome) and all secondary outcomes including physical activity behaviors, theory-based constructs, quality of life, media literacy, anthropometric, and biological outcomes.

Results

Targeting a medically-underserved rural region in southwest Virginia, 1056 adult participants were screened, 620 (59 %) eligible, 301 (49 %) enrolled and randomized, and 296 included in these 2015 analyses. Participants were 93 % Caucasian, 81 % female, 31 % ≤ high-school educated, 43 % < $14,999 household income, and 33 % low health literate. Retention rates (74 %) and program engagement was not statistically different between conditions. Compared to MoveMore, SIPsmartER participants significantly decreased SSB kcals and BMI at 6 months. SIPsmartER participants significantly decreased SSB intake by 227 (95 % CI = −326,−127, p < 0.001) kcals/day from baseline to 6 months when compared to the decrease of 53 (95 % CI = −88,−17, p < 0.01) kcals/day among MoveMore participants (p < 0.001). SIPsmartER participants decreased BMI by 0.21 (95 % CI = −0.35,−0.06; p < 0.01) kg/m² from baseline to 6 months when compared to the non-significant 0.10 (95 % CI = −0.23, 0.43; NS) kg/m² gain among MoveMore participants (p < 0.05). Significant 0–6 month effects were observed for about half of the theory-based constructs, but for no biological outcomes. Health literacy status did not influence retention rates, engagement or outcomes.

Conclusions

SIPsmartER is an effective intervention to decrease SSB consumption among adults and is promising for translation into practice settings. SIPsmartER also yielded small, yet significant, improvements in BMI. By using health literacy-focused strategies, the intervention was robust in achieving reductions for participants of varying health literacy status.

Trial registration

Clinicaltrials.gov; ID: NCT02193009.

Prediabetes Phenotype Influences Improvements in Glucose Homeostasis with Resistance Training

Purpose

To determine if prediabetes phenotype influences improvements in glucose homeostasis with resistance training (RT).

Methods

Older, overweight individuals with prediabetes (n = 159; aged 60±5 yrs; BMI 33±4 kg/m²) completed a supervised RT program twice per week for 12 weeks. Body weight and composition, strength, fasting plasma glucose, 2-hr oral glucose tolerance, and Matsuda-Defronza estimated insulin sensitivity index (ISI) were assessed before and after the intervention. Participants were categorized according to their baseline prediabetes phenotype as impaired fasting glucose only (IFG) (n = 73), impaired glucose tolerance only (IGT) (n = 21), or combined IFG and IGT (IFG/IGT) (n = 65).

Results

Chest press and leg press strength increased 27% and 18%, respectively, following the 12-week RT program (both p<0.05). Waist circumference (-1.0%; pre 109.3±10.3 cm, post 108.2±10.6 cm) and body fat (-0.6%; pre 43.7±6.8%, post 43.1±6.8%) declined, and lean body mass (+1.3%; pre 52.0±10.4 kg, post 52.7±10.7 kg) increased following the intervention. Fasting glucose concentrations did not change (p>0.05) following the intervention. However, 2-hr oral glucose tolerance improved in those with IGT (pre 8.94±0.72 mmol/l, post 7.83±1.11 mmol/l, p<0.05) and IFG/IGT (pre 9.66±1.11mmol/l, post 8.60±2.00 mmol/l) but not in those with IFG (pre 6.27±1.28mmol/l, post 6.33± 1.55 mmol/l). There were no significant changes in ISI or glucose area under the curve following the RT program.

Conclusions

RT without dietary intervention improves 2-hr oral glucose tolerance in individuals with prediabetes. However, the improvements in glucose homeostasis with RT appear limited to those with IGT or combined IFG and IGT.

Trial Registration

ClinicalTrials.gov: NCT01112709

Beverage Choices of Adolescents and Their Parents Using the Theory of Planned Behavior: A Mixed Methods Analysis

BACKGROUND

Added sugar intake in the form of sugar-sweetened beverages (SSBs) has been considered a contributor to weight gain and cardiometabolic dysfunction in adults and youth. Adolescents are some of the highest consumers of added sugars, taking in ∼16% of their total calories from added sugars with ∼40% of these calories coming from SSBs. Food preferences and self-regulation of dietary intake by youth can be influenced by parents.

OBJECTIVE

To evaluate the effectiveness of the Theory of Planned Behavior (TPB) in understanding and predicting adolescents' SSB consumption, identify which constructs are the most important when evaluating SSB consumption in adolescents, and determine whether and how adolescents' beverage choices are influenced by parents' reactions to their beverage choices.

DESIGN

Measurements for this cross-sectional study included four record-assisted 24-hour dietary recalls and responses to an SSB-specific TPB questionnaire from 100 adolescents. Consenting parents completed a beverage intake questionnaire, a TPB questionnaire, and the Parent Response to Beverage Choice Questionnaire.

RESULTS

The TPB explained 34% of the variance in adolescents' and parents' intention to limit SSBs to <1cup/day. Parents' perceived behavioral control (b=1.35; P=0.002) and adolescents' subjective norms (b=0.57; P=0.001) were the strongest predictors of intention, and intention was the strongest predictor of SSB consumption in both adolescents and parents (b=-37 [P=0.026] and b=-49 [P=0.003], respectively). The TPB explained more variance in parent SSB consumption (R(2)=0.38) than adolescents (R(2)=0.22). Parents did more discouraging of SSBs and encouraging of non-SSBs. Adolescents' intention to limit SSB consumption moderated the relationship between parents' reactions encouraging SSBs and adolescents' predicted SSB consumption (P=0.021).

CONCLUSIONS

The TPB explained a small but significant amount of variance in adolescents' SSB consumption. When addressing adolescent SSB intake, people in addition to parents may influence their intentions and SSB consumption.

Probiotic supplementation and trimethylamine-N-oxide production following a high-fat diet

OBJECTIVE

The objective of this study was to test the hypothesis that the multi-strain probiotic VSL#3 would attenuate the increase in fasting plasma concentrations of trimethylamine-N-oxide (TMAO) following a high-fat diet.

METHODS

Nineteen healthy, non-obese males (18-30 years) participated in the present study. Following a 2-week eucaloric control diet, subjects were randomized to either VSL#3 (900 billion live bacteria) or placebo (cornstarch) during the consumption of a hypercaloric (+1,000 kcal day(-1) ), high-fat diet (55% fat) for 4 weeks. Plasma TMAO, L-carnitine, choline, and betaine (UPLC-MS/MS) were measured at baseline and following a high-fat diet.

RESULTS

Plasma TMAO significantly increased 89% ± 66% vs. 115% ± 61% in both the VSL#3 and placebo groups, respectively; however, the magnitude of change in plasma TMAO was not different (P > 0.05) between them. Plasma L-carnitine, choline, and betaine concentrations did not increase following the high-fat diet in either group.

CONCLUSIONS

A high-fat diet increases plasma TMAO in healthy, normal-weight, young males. However, VSL#3 treatment does not appear to influence plasma TMAO concentrations following a high-fat diet. Future studies are needed to determine whether other therapeutic strategies can attenuate the production of TMAO.

Probiotic supplementation attenuates increases in body mass and fat mass during high-fat diet in healthy young adults

OBJECTIVE

The objective was to determine the effects of the probiotic, VSL#3, on body and fat mass, insulin sensitivity, and skeletal muscle substrate oxidation following 4 weeks of a high-fat diet.

METHODS

Twenty non-obese males (18-30 years) participated in the study. Following a 2-week eucaloric control diet, participants underwent dual X-ray absorptiometry to determine body composition, an intravenous glucose tolerance test to determine insulin sensitivity, and a skeletal muscle biopsy for measurement of in vitro substrate oxidation. Subsequently, participants were randomized to receive either VSL#3 or placebo daily during 4 weeks of consuming a High-fat (55% fat), hypercaloric diet (+1,000 kcal day(-1) ). Participants repeated all measurements following the intervention.

RESULTS

Body mass (1.42 ± 0.42 kg vs. 2.30 ± 0.28 kg) and fat mass (0.63 ± 0.09 kg vs. 1.29 ± 0.27 kg) increased less following the High-fat diet in the VSL#3 group compared with placebo. However, there were no significant changes in insulin sensitivity or in vitro skeletal muscle pyruvate and fat oxidation with the High-fat diet or VSL#3.

CONCLUSIONS

VSL#3 supplementation appears to have provided some protection from body mass gain and fat accumulation in healthy young men consuming a High-fat and high-energy diet.

The effect of prebiotic supplementation with inulin on cardiometabolic health: Rationale, design, and methods of a controlled feeding efficacy trial in adults at risk of type 2 diabetes

Prediabetes is associated with low-grade chronic inflammation that increases the risk for developing type 2 diabetes (T2D) and cardiovascular disease (CVD). An elevated lipopolysaccharide concentration, associated with dysbiosis of the intestinal microbiota, has been implicated in the development of both T2D and CVD. Selective modulation of the intestinal microbiota with prebiotics reduces intestinal permeability and endotoxin concentrations, inflammation, and metabolic dysfunction in rodents. The effect of prebiotic supplementation on cardio-metabolic function in humans at risk for T2D is not known. The primary aim of this trial is to determine the influence of prebiotic supplementation with inulin on insulin sensitivity and skeletal muscle metabolic flexibility in adults at risk for T2D. We hypothesize that prebiotic supplementation with inulin will improve insulin sensitivity and skeletal muscle metabolic flexibility. We will randomize 48 adults (40-75 yrs) with prediabetes or a score ≥ 5 on the American Diabetes Association (ADA) risk screener to 6 weeks of prebiotic supplementation with inulin (10 g/day) or placebo. Subjects will be provided with all food for the duration of the study, to avoid potential confounding through differences in dietary intake between individuals. Intestinal permeability, serum endotoxin concentrations, insulin sensitivity, skeletal muscle metabolic flexibility, endothelial function, arterial stiffness, and fecal bacterial composition will be measured at baseline and following treatment. The identification of prebiotic supplementation with inulin as an efficacious strategy for reducing cardio-metabolic risk in individuals at risk of T2D could impact clinical practice by informing dietary recommendations and increasing acceptance of prebiotics by the scientific and medical community.

An evaluation of the readability of drinking water quality reports: a national assessment

The United States Environmental Protection Agency mandates that community water systems (or water utilities) provide annual consumer confidence reports (CCRs)--water quality reports--to their consumers. These reports encapsulate information regarding sources of water, detected contaminants, regulatory compliance, and educational material. These reports have excellent potential for providing the public with accurate information on the safety of tap water, but there is a lack of research on the degree to which the information can be understood by a large proportion of the population. This study evaluated the readability of a nationally representative sample of 30 CCRs, released between 2011 and 2013. Readability (or 'comprehension difficulty') was evaluated using Flesch-Kincaid readability tests. The analysis revealed that CCRs were written at the 11th-14th grade level, which is well above the recommended 6th-7th grade level for public health communications. The CCR readability ease was found to be equivalent to that of the Harvard Law Review journal. These findings expose a wide chasm that exists between current water quality reports and their effectiveness toward being understandable to US residents. Suggestions for reorienting language and scientific information in CCRs to be easily comprehensible to the public are offered.

A systematic literature review and meta-analysis: The Theory of Planned Behavior's application to understand and predict nutrition-related behaviors in youth

BACKGROUND

Efforts to reduce unhealthy dietary intake behaviors in youth are urgently needed. Theory-based interventions can be effective in promoting behavior change; one promising model is the Theory of Planned Behavior (TPB).

PURPOSE

The aim of this study was to determine, using a systematic literature review, how the TPB has been applied to investigate dietary behaviors, and to evaluate which constructs are associated with dietary behavioral intentions and behaviors in youth.

METHODS

Publications were identified by searching electronic databases, contacting experts in the field, and examining an evolving Internet-based TPB-specific bibliography. Studies including participants aged 2-18years, all TPB constructs discernible and measured with a description of how the variables were assessed and analyzed, were published in English and peer-reviewed journals, and focused on nutrition-related behaviors in youth were identified. Accompanying a descriptive statistical analysis was the calculation of effect sizes where possible, a two-stage meta-analysis, and a quality assessment using tenants from the Consolidated Standards of Reporting Trials (CONSORT) and Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statements.

RESULTS

Thirty-four articles, including three intervention studies, were reviewed. The TPB was most often used to evaluate healthy eating and sugary snack and beverage consumption. Attitude had the strongest relationship with dietary behavioral intention (mean r=0.52), while intention was the most common predictor of behavior performance (mean r=0.38; both p<0.001). All three interventions revealed beneficial outcomes when using the TPB (e.g. η(2)=0.51 and ds=0.91, 0.89, and 0.79); extending the Theory with implementation intentions may enhance its effectiveness (e.g. η(2)=0.76).

CONCLUSIONS

Overall, the TPB may be an effective framework to identify and understand child and adolescent nutrition-related behaviors, allowing for the development of tailored initiatives targeting poor dietary practices in youth. However, support from the literature is primarily from observational studies and a greater effort towards examining these relationships within intervention studies is needed.

Short-term high-fat diet increases postprandial trimethylamine-N-oxide in humans

The gut microbiota plays an obligatory role in the metabolism of nutrients containing trimethylamine moieties, such as L-carnitine and choline, leading to the production of the proatherogenic trimethylamine-N-oxide (TMAO). We hypothesized that a short-term, high-fat diet would increase fasting and postprandial plasma concentrations of TMAO in response to a high-fat meal challenge. Following a 2-week eucaloric control diet, 10 nonobese men (18-30 years) consumed a eucaloric, high-fat diet (55% fat) for 5 days. Plasma TMAO was measured after a 12-hour fast and each hour after for 4 hours following a high-fat meal (63% fat) at baseline and after the high-fat diet using ultraperformance liquid chromatography/ tandem mass spectrometry. Fasting plasma TMAO did not increase significantly following the high-fat diet (1.83 ± 0.21 vs 1.6 ± 0.24 μmol/L). However, plasma TMAO was higher at hour 1 (2.15 ± 0.28 vs 1.7 ± 0.30 μmol/L), hour 2 (2.3 ± 0.29 vs 1.8 ± 0.32 μmol/L), hour 3 (2.4 ± 0.34 vs 1.58 ± 0.19 μmol/L), and hour 4 (2.51 ± 0.33 vs 1.5 ± 0.12 μmol/L) (all P < .05) following the high-fat diet as compared with the baseline postprandial response. In conclusion, a short-term, high-fat diet does not increase fasting plasma TMAO concentrations but appears to increase postprandial TMAO concentrations in healthy, nonobese, young men. Future studies are needed to determine the mechanisms responsible for these observations.

The Healthy Beverage Index Is Associated with Reduced Cardiometabolic Risk in US Adults: A Preliminary Analysis

BACKGROUND AND OBJECTIVE

Beverage recommendations exist, but few evaluate overall beverage intake quality. Our objective was to develop a scoring algorithm for assessing beverage intake quality among US adults (aged ≥19 years), and to examine the association between overall beverage quality and cardiometabolic risk.

DESIGN

We developed a scoring algorithm, similar to the Healthy Eating Index-2010, using recommendations for total beverage energy, meeting fluid requirements, and consuming within recommended limits for beverage subgroups (eg, low-fat milk, fruit juice). Multiple scoring systems were evaluated. The final scoring system, which consisted of 10 components, was applied to the average of 2 days of 24-hour dietary intake data for adults (aged ≥19 years) from the National Health and Nutrition Examination Survey (NHANES), 2005-2010.

STATISTICAL ANALYSES PERFORMED

Poisson regression models stratified by sex and body mass index multivariables were used to examine the cross-sectional association between the Healthy Beverage Index (HBI) score and cardiometabolic outcomes.

RESULTS

The 10-item index had a mean±standard deviation score of 63±16 from a possible 100 points. Each 10-point higher HBI score was associated with lower odds ratios for hypertension (men and women); high fasting insulin level, high fasting glucose level, and high low-density lipoprotein cholesterol level (women and overweight/obese men), low high-density lipoprotein cholesterol level (women), and high C-reactive protein level (men).

CONCLUSIONS

We found positive associations between higher HBI scores and more favorable lipid profiles; hypertension risk; and, among men, C-reactive protein levels. These preliminary results suggest that the HBI could be a valuable tool to evaluate overall beverage intake quality in adults. More research is needed to understand whether improvements in beverage quality and, thus, HBI score, are associated with beneficial changes in health.

A Dual-Carbon-and-Nitrogen Stable Isotope Ratio Model Is Not Superior to a Single-Carbon Stable Isotope Ratio Model for Predicting Added Sugar Intake in Southwest Virginian Adults

BACKGROUND

An objective measure of added sugar (AS) and sugar-sweetened beverage (SSB) intake is needed. The δ(13)C value of finger-stick blood is a novel validated biomarker of AS/SSB intake; however, nonsweetener corn products and animal protein also carry a δ(13)C value similar to AS sources, which may affect blood δ(13)C values. The δ(15)N value of blood has been proposed as a "correction factor" for animal protein intake.

OBJECTIVES

The objectives were to 1) identify foods associated with δ(13)C and δ(15)N blood values, 2) determine the contribution of nonsweetener corn to the diet relative to AS intake, and 3) determine if the dual-isotope model (δ(13)C and δ(15)N) is a better predictor of AS/SSB intake than δ(13)C alone.

METHODS

A cross-sectional sample of southwest Virginian adults (n = 257; aged 42 ± 15 y; 74% overweight/obese) underwent dietary intake assessments and provided finger-stick blood samples, which were analyzed for δ(13)C and δ(15)N values by using natural abundance stable isotope mass spectrometry. Statistical analyses included ANOVAs, paired-samples t tests, and multiple linear regressions.

RESULTS

The mean ± SD daily AS intake was 88 ± 59 g and nonsweetener corn intake was 13 ± 13 g. The mean δ(13)C value was -19.1 ± 0.9‰, which was significantly correlated with AS and SSB intakes (r = 0.32 and 0.39, respectively; P ≤ 0.01). The δ(13)C value and nonsweetener corn intake and the δ(15)N value and animal protein intake were not correlated. AS intake was significantly greater than nonsweetener corn intake (mean difference = 76.2 ± 57.2 g; P ≤ 0.001). The δ(13)C value was predictive of AS/SSB intake (β range: 0.28-0.35; P ≤ 0.01); however, δ(15)N was not predictive and minimal increases in R(2) values were observed when the δ(15)N value was added to the model.

CONCLUSIONS

The data do not provide evidence that the dual-isotope method is superior for predicting AS/SSB intakes within a southwest Virginian population. Our results support the potential of the δ(13)C value of finger-stick blood to serve as an objective measure of AS/SSB intake. This trial was registered at clinicaltrials.gov as NCT02193009.

Theory-based approach for maintaining resistance training in older adults with prediabetes: adherence, barriers, self-regulation strategies, treatment fidelity, costs

Effectively preventing and treating chronic diseases through health behavior changes often require intensive theory- and evidence-based intervention including long-term maintenance components. We assessed the efficacy of theory-based maintenance approaches varying by dose for persistently performing resistance training (RT) with the hypothesis that a higher-dose social cognitive theory (SCT) approach would produce greater RT adherence than lower-dose Standard. The Resist-Diabetes study first established 2×/week resistance training (RT) in a 3-month supervised intervention in older (50-69 years, N = 170), overweight to obese (BMI 25-39.9 kg/m(2)) previously inactive adults who fit prediabetes criteria (fasting glucose concentration = 95-125 mg/dl; oral glucose tolerance test 2-h glucose concentration = 140-199 mg/dl or both). After the supervised phase, participants (N = 159) were then randomly assigned to one of two conditions for transition (3 weeks) and then RT alone in community settings for extended contact, maintenance (6 months), and then no contact (6 months). SCT featured continued tailored, interactive personal, and web-based check-ups focused on RT, self-regulation, and a barrier/strategies approach. Standard involved low-dose, generic personal, and web-based check-ups within the same theoretical approach. SCT and Standard both resulted in similar RT, 2×/week adherence during maintenance (74.4 %) and no-contact phases (53.1 %). Cost analysis indicated the Standard intervention for transition and maintenance was inexpensive ($160). Standard can be translated into practice with the potential for continuous contact and persistence in RT beyond the typical program maintenance phase.

Associations among chronic disease status, participation in federal nutrition programs, food insecurity, and sugar-sweetened beverage and water intake among residents of a health-disparate region

OBJECTIVE

To determine whether sociodemographic characteristics, food security status, participation in federal nutrition programs (Supplemental Nutrition Assistance Program [SNAP] or Special Supplemental Nutrition Program for Women, Infants, and Children [WIC]), and chronic disease status were associated with adherence to water and sugar-sweetened beverage (SSB) intake recommendations.

DESIGN

Cross-sectional, random-digit phone survey with questions from the Behavioral Risk Factor Surveillance System and beverage intake questionnaire.

PARTICIPANTS

Residents of a medically underserved, rural area.

MAIN OUTCOME MEASURES

Water and SSB intake.

ANALYSIS

Descriptive statistics, chi-square and 1-way ANOVA, and linear and logistic regression.

RESULTS

The sample consisted of 930 respondents (aged 56 ± 17 years; 35% non-white); reported food insecurity and SNAP and WIC participation were 37%, 29%, and 8%, respectively. Prevalent health conditions included overweight/obesity (69%), diabetes (19%), and hypertension (45%). Water recommendations were more likely to be met (72%; mean intake, 31 ± 19 fluid oz) than SSB (41%; mean intake, 246 ± 297 kcal). Food insecurity and SNAP/WIC participation were not associated with meeting recommendations, but those reporting ≥ 1 chronic disease were more likely to meet SSB recommendations (odds ratio, 2.42; P = .02).

CONCLUSIONS AND IMPLICATIONS

Odds of achieving SSB but not water recommendations were greater among individuals with a chronic disease. Efforts to communicate beverage recommendations to at-risk groups are needed.

Early skeletal muscle adaptations to short-term high-fat diet in humans before changes in insulin sensitivity

OBJECTIVE

The purpose of this investigation was to understand the metabolic adaptations to a short-term (5 days), isocaloric, high-fat diet (HFD) in healthy, young males.

METHODS

Two studies were undertaken with 12 subjects. Study 1 investigated the effect of the HFD on skeletal muscle substrate metabolism and insulin sensitivity. Study 2 assessed the metabolic and transcriptional responses in skeletal muscle to the transition from a fasted to fed state using a high-fat meal challenge before and after 5 days of the HFD.

RESULTS

Study 1 showed no effect of a HFD on skeletal muscle metabolism or insulin sensitivity in fasting samples. Study 2 showed that a HFD elicits significant increases in fasting serum endotoxin and disrupts the normal postprandial excursions of serum endotoxin, as well as metabolic and transcriptional responses in skeletal muscle. These effects after 5 days of the HFD were accompanied by an altered fasting and postprandial response in the ratio of phosphorylated- to total-p38 protein. These changes all occurred in the absence of alterations in insulin sensitivity.

CONCLUSIONS

Our findings provide evidence for early biological adaptations to high-fat feeding that proceed and possibly lead to insulin resistance.