Insulin resistance before type 2 diabetes onset is associated with increased risk of albuminuria after diabetes onset: A prospective cohort study

AIM

Reduced renal insulin signalling is implicated in the pathogenesis of albuminuria. We sought to investigate whether insulin action and secretion, measured before diabetes onset, are associated with the development of albuminuria after diabetes onset.

MATERIALS AND METHODS

Baseline body composition, insulin sensitivity by hyperinsulinaemic-euglycaemic clamp at submaximal and maximal insulin stimulation (240 and 2400 pmol/m2/min; M-low and M-high), and insulin secretion by intravenous glucose tolerance test [acute insulin response (AIR)] were measured in 170 Southwestern Indigenous American adults who subsequently developed diabetes. After diabetes onset and during the median follow-up of 13.6 years, 81 participants (48%) developed albuminuria (urine albumin-to-creatinine ratio ≥30 mg/g). Separate associations of M-low, M-high and AIR (per 1-SD change) with the risk of albuminuria were assessed by Cox regression models adjusted for age, sex and body fat (%).

RESULTS

Participants who developed albuminuria were of similar age (26.4 ± 5.4 vs. 27.5 ± 6.1 years), sex (46% vs. 48% male), body fat (36.4 ± 7.5 vs. 35.7 ± 7.9%) and AIR [2.3 ± 0.3 vs. 2.3 ± 0.3, pmol/L (log)] as those who did not develop albuminuria but had lower insulin sensitivity [M-low: 0.33 ± 0.08 vs. 0.36 ± 0.12, p = .03; M-high: 0.87 ± 0.11 vs. 0.91 ± 0.12, p = .02; mg/kg-metabolic body size/min (log)]. In separate adjusted models, lower M-low and M-high were both associated with an increased risk for albuminuria [hazard ratio (HR) 1.51, 95% confidence interval (CI) 1.14, 2.00, p = .004; HR 1.31, 95% CI 1.06, 1.63, p = .01), whereas AIR was not (HR 1.15, 95% CI 0.87, 1.56, p = .3).

CONCLUSIONS

Lower insulin sensitivity is associated with the development of albuminuria, suggesting a role for insulin signalling in the pathogenesis of proteinuria.

Impaired metabolic flexibility to fasting is associated with increased ad libitum energy intake in healthy adults

OBJECTIVE

We investigated how changes in 24-h respiratory exchange ratio (RER) and substrate oxidation during fasting versus an energy balance condition influence subsequent ad libitum food intake.

METHODS

Forty-four healthy, weight-stable volunteers (30 male and 14 female; mean [SD], age 39.3 [11.0] years; BMI 31.7 [8.3] kg/m2) underwent 24-h energy expenditure measurements in a respiratory chamber during energy balance (50% carbohydrate, 30% fat, and 20% protein) and 24-h fasting. Immediately after each chamber stay, participants were allowed 24-h ad libitum food intake from computerized vending machines.

RESULTS

Twenty-four-hour RER decreased by 9.4% (95% CI: -10.4% to -8.5%; p < 0.0001) during fasting compared to energy balance, reflecting a decrease in carbohydrate oxidation (mean [SD], -2.6 [0.8] MJ/day; p < 0.0001) and an increase in lipid oxidation (2.3 [0.9] MJ/day; p < 0.0001). Changes in 24-h RER and carbohydrate oxidation in response to fasting were correlated with the subsequent energy intake such that smaller decreases in fasting 24-h RER and carbohydrate oxidation, but not lipid oxidation, were associated with greater energy intake after fasting (r = 0.31, p = 0.04; r = 0.40, p = 0.007; and r = -0.27, p = 0.07, respectively).

CONCLUSIONS

Impaired metabolic flexibility to fasting, reflected by an inability to transition away from carbohydrate oxidation, is linked with increased energy intake.

An algorithm to simulate missing data for mixed meal tolerance test response curves

BACKGROUND

Response curves formed by analyte concentrations measured at sampled time points after consuming a mixed meal are increasingly being used to characterize responses to differing diets. Unfortunately, owing to a variety of reasons, analyte concentrations for some of the time points may be missing.

OBJECTIVES

This study aimed to develop an algorithm to estimate the missing values at sampled time points in the analyte response curve to a mixed meal tolerance test (MMTT).

METHODS

We developed an algorithm to simulate the missing postprandial concentration values for an MMTT. The algorithm was developed to handle any number of missing values for 2 or less consecutive missing values. The algorithm was tested on MMTT response curve data for glucose and triglyceride measurements in data from 3 different studies with 2119 postprandial MMTT response curves. The algorithm was validated by removing concentration values that were not missing and replacing them with the algorithm simulated values. The AUC error between the actual curve and simulated curves were also calculated. A web-based application was developed to automatically simulate missing values for an uploaded MMTT data set.

RESULTS

The algorithm was programmed in Python and the resulting web-based application and a video tutorial were provided. The validation indicated good agreement between actual and simulated values with error increasing for less frequently sampled time points. The study with the average minimum error of glucose concentrations was 6.2 ± 2.1 mg/dL and study with the average maximum error of glucose concentrations was 11.3 ± 4.7 mg/dL. Triglycerides had 16.1 ± 6.2 mg/dL average error. The AUC error was small ranging between 0.01% and 0.28%.

CONCLUSIONS

The presented algorithm reconstructs postprandial response curves with estimations of values that are missing.

Higher glucose and insulin responses to a mixed meal are associated with increased risk of diabetic retinopathy in Indigenous Americans

PURPOSE

Prior research has focused on glucose/insulin responses to meal challenges to create personalized diets to improve health, though it is unclear if these responses predict chronic diseases. We aimed to identify glucose and insulin responses to a mixed meal tolerance test (MMTT) that predict the development of diabetic retinopathy (DR) and compare the predictive abilities with the oral glucose tolerance test (OGTT).

METHODS

Indigenous American adults without diabetes (n = 168) underwent a 4-h MMTT, body composition assessment, and a 3-h OGTT at baseline. During follow-up (median 13.4 years), DR was diagnosed by direct ophthalmoscopy (n = 28) after onset of type 2 diabetes. Total and incremental area under the curve (AUC and iAUC) were calculated from glucose/insulin responses after the MMTT and OGTT.

RESULTS

In separate Cox proportional hazards models adjusted for age, sex, and body fat (%), MMTT glucose AUCs (180-min and 240-min) and iAUC (180-min) predicted DR (HR 1.50, 95% CI 1.06, 2.12; HR 1.50, 95% CI 1.05, 2.14; HR 1.58, 95% CI 1.01, 2.46). The predictive abilities were better than the fasting OGTT glucose (p < 0.01) but similar to the 120-min OGTT glucose (p = 0.53). MMTT insulin AUCs (180-min and 240-min) and iAUC (180-min) also predicted DR (HR 1.65, 95% CI 1.09, 2.51; HR 1.58, 95% CI 1.00, 2.35; HR 1.53 95% CI 1.06, 2.22) while insulin AUC and iAUC from the OGTT did not (p > 0.05).

CONCLUSIONS

Higher MMTT glucose and insulin responses predicted DR and were comparable to the OGTT, supporting the use of a meal challenge for precision nutrition.

TRIAL REGISTRATIONS

Clinical Trial Registry: ClinicalTrials.gov identifier: NCT00340132, NCT00339482.

Twenty-Four-Hour Urinary Sugars Biomarker in a Vending Machine Intake Paradigm in a Diverse Population

Accurately measuring dietary sugars intake in large-scale epidemiological studies is necessary to understand dietary sugars' true impact on health. Researchers have developed a biomarker that can be used to assess total sugars intake. Our objective is to test this biomarker in diverse populations using an ad libitum intake protocol. Healthy adult participants (n = 63; 58% Indigenous Americans/Alaska Natives; 60% male; BMI (mean ± SD) = 30.6 ± 7.6 kg.m2) were admitted for a 10-day inpatient stay. On day 2, body composition was measured by DXA, and over the last 3 days, ad libitum dietary intake was measured using a validated vending machine paradigm. Over the same days, participants collected daily 24 h urine used to measure sucrose and fructose. The 24 h urinary sucrose and fructose biomarker (24hruSF) (mg/d) represents the sum of 24 h urinary sucrose and fructose excretion levels. The association between the 3-day mean total sugars intake and log 24uSF level was assessed using the Pearson correlation. A linear mixed model regressing log-biomarker on total sugars intake was used to investigate further the association between biomarker, diet, and other covariates. Mean (S.D.) total sugars intake for the group was 197.7 g/d (78.9). Log 24uSF biomarker was moderately correlated with total sugars intake (r = 0.33, p = 0.01). In stratified analyses, the correlation was strongest in females (r = 0.45, p = 0.028), the 18-30 age group (r = 0.44, p = 0.079), Indigenous Americans (r = 0.51, p = 0.0023), and the normal BMI category (r = 0.66, p = 0.027). The model adjusted for sex, age, body fat percent, and race/ethnicity demonstrated a statistically significant association between 24uSF and total sugars intake (β = 0.0027, p < 0.0001) and explained 31% of 24uSF variance (marginal R2 = 0.31). Our results demonstrated a significant relationship between total sugars intake and the 24uSF biomarker in this diverse population. However, the results were not as strong as those of controlled feeding studies that investigated this biomarker.

Dietary Adherence Is Associated with Perceived Stress, Anhedonia, and Food Insecurity Independent of Adiposity

We examined whether perceived stress, anhedonia, and food insecurity were associated with dietary adherence during a 6-week intervention. Sixty participants (23 m; 53 ± 14 y) completed psychosocial measures and were provided with full meals. Individuals with obesity were randomized to a weight-maintaining energy needs (WMENs) (n = 18; BMI 33 ± 4) or a 35% calorie-reduced diet (n = 19; BMI 38 ± 9); normal-weight individuals (n = 23; BMI 23 ± 2) were assigned to a WMENs diet. Adherence scores were determined via weekly assessments and daily ecological momentary assessments (EMAs) of real-time behavior in a natural environment. Perceived stress and anhedonia were associated with % body fat (all r-values > 0.25, all p-values < 0.05), but food insecurity and adherence were not. Higher perceived stress (r = -0.31, p = 0.02), anhedonia (r = -0.34, p = 0.01), and food insecurity (r = -0.27, p = 0.04) were associated with lower adherence scores, even after adjusting for age, sex, and % body fat. In all adjusted models, % body fat was not associated with adherence. Higher measures of stress, anhedonia, and food insecurity predicted lower adherence independently of body fat, indicating that psychosocial factors are important targets for successful adherence to dietary interventions, regardless of body size.

Investigation of seasonality of human spontaneous physical activity and energy expenditure in respiratory chamber in Phoenix, Arizona

OBJECTIVE

The existence of seasonal changes in energy metabolism is uncertain. We investigated the relationship between the seasons and spontaneous physical activity (SPA), energy expenditure (EE), and other components measured in a respiratory chamber.

METHODS

Between 1985-2005, 671 healthy adults (aged 28.8 ± 7.1 years; 403 men) in Phoenix, Arizona had a 24-hour stay in the respiratory chamber equipped with radar sensors; SPA (expressed as a percentage over the time interval), the energy cost of SPA, EE, and respiratory exchange ratio (RER) were measured.

RESULTS

In models adjusted for known covariates, SPA (%) was lower during summer (7.2 ± 2.9, p = 0.0002), spring (7.5 ± 2.9, p = 0.025), and fall (7.6 ± 3, p = 0.038) compared to winter (8.3 ± 3.5, reference). Conversely, energy cost of SPA (kcal/h/%) was higher during summer (2.18 ± 0.83, p = 0.0008), spring (2.186 ± 0.83, p = 0.017), and fall (2.146 ± 0.75, p = 0.038) compared to winter (2.006 ± 0.76). Protein (292 ± 117 kcal/day, β = -21.2, p = 0.08) oxidation rates was lower in the summer compared to winter. Carbohydrate and lipid oxidation rates (kcal/day) did not differ across seasons. RER and 24-h EE did not differ by season.

CONCLUSION

SPA, representing fidgeting-like behavior in the chamber, demonstrated a winter peak and summer nadir in humans living in a desert climate. These findings indicate that the physiological propensity for movement may be affected by seasonal factors.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identifiers: NCT00340132, NCT00342732.

Greater anhedonia scores in healthy individuals are associated with less decline in 24-hour energy expenditure with fasting: Evidence for a link between behavioral traits and spendthrift phenotype

Obesity rates are increasing and affecting mental health. It is important to understand how behavioral traits such as anhedonia are associated with physiologic traits that may predict weight-change in clinical and non-clinical populations. We studied whether 24-hour energy expenditure (24hEE) changes with fasting and overfeeding are associated with anhedonia in a healthy cohort. We performed behavioral assessments (physical anhedonia scale (PAS) and inventory for depressive symptoms (IDS)) followed by measures of 24hEE and urinary catecholamines in a whole-room indirect calorimeter (respiratory chamber) during energy balance, and then randomly during fasting and 2 different overfeeding diets. Participants (n=98) were medically healthy, between 18 and 55 years of age, with normal glucose regulation and weight-stable 6 months before admission. Women were premenopausal and not pregnant. Higher PAS was significantly associated with lesser decrease in 24hEE with fasting and higher urinary catecholamine excretion rates - consistent with spendthrift metabolism. As IDS increased, the association between anhedonia and the change in 24hEE from energy balance to fasting decreased (B-values were lower for change in EE). Here, higher PAS scores may reflect the ability to respond with appropriate homeostatic reactions which balance energy needs. IDS scores blunting this response may explain how anhedonia and depression can lead to weight gain.

Validation of Total Water Intake from the Automated Self-Administered 24-h Recall, 4-d Food Records, and a Food Frequency Questionnaire Using Doubly Labeled Water

BACKGROUND

Although prior evidence indicates that water intake is important for health, the ability to accurately measure community-dwelling intake is limited. Only a few studies have evaluated self-reported water intake against an objective recovery biomarker.

OBJECTIVES

The aim was to compare preformed water intakes (all sources including food) by multiple Automated Self-Administered 24-h recalls (ASA24s), food frequency questionnaires (FFQs), and 4-d food records (4DFRs) against a recovery biomarker, doubly labeled water (DLW), to assess measurement error.

METHODS

Over 1 y, 1082 women and men (50%), aged 50 to 74 y, were asked to complete 6 ASA24s, 2 FFQs, 2 unweighted 4DFRs, and an administration of DLW (n = 686). Geometric means of water intake by self-report tools were compared with DLW. Attenuation factors and correlation coefficients between self-reported and the recovery biomarker (DLW) were estimated.

RESULTS

Mean water intakes by DLW were 2777 mL/d (interquartile range, 2350 to 3331) in women and 3243 mL/d (interquartile range, 2720 to 3838) in men. Compared with DLW, water intake was underestimated by 18% to 31% on ASA24s and 43% to 44% on 4DFRs. Estimated geometric means from FFQs differed from DLW by -1% to +13%. For a single ASA24, FFQ, and 4DFR, attenuation factors were 0.28, 0.27, and 0.32 and correlation coefficients were 0.46, 0.48, and 0.49, respectively. Repeated use of 6 ASA24s, 2 FFQs, and 2 4DFRs improved attenuation factors to 0.43, 0.32, and 0.39 and correlation coefficients to 0.58, 0.53, and 0.54, respectively.

CONCLUSIONS

FFQs may better estimate population means for usual water intake compared with ASA24 and 4DFR. Similar attenuation factors and correlation coefficients across all self-report tools indicate that researchers have 3 feasible options if the goal is understanding intake-disease relationships. The findings are useful for planning future nutrition studies that set policy priorities for populations and to understand the health impact of water. This trial was registered at clinicaltrials.gov as NCT03268577.

Disinhibition augments thirst perception from two dehydrating stimuli in men

Physiological systems controlling water and energy ingestion are coordinated. Whether maladaptive eating behavior and appetite for water are linked is unknown. Thus, we sought to investigate the association between maladaptive eating and both thirst and water drinking behavior with two dehydrating conditions. Twenty-two lean men and 20 men with obesity (mean age 32.3 ± 8.4 years and 30.0 ± 11.1 years, respectively) completed the Three-Factor Eating Questionnaire (TFEQ) and Gormally Binge Eating Scale. On separate days, volunteers were dehydrated by a 2-h hypertonic saline infusion and a 24-h water deprivation, and thirst was measured on a 100-mm visual analogue scale (VAS) during each procedure. After each dehydrating condition, ad libitum water intake was measured. In the saline infusion, higher Disinhibition on the TFEQ was associated with thirst in the lean group (β = 4.2 mm VAS, p = 0.03) but not in the group with obesity (p = 0.51). In the water-deprivation condition, higher Disinhibition was also associated with thirst in the lean group (β = 5.6 mm VAS, p = 0.01) with the strength of relationship being 3.5-fold stronger than that observed in the group with obesity (β = 1.6 mm VAS, p = 0.0003). Hunger, Restraint, and binge-eating scores were not associated with thirst in either dehydrating condition (all p > 0.05). Maladaptive eating behaviors were not associated with ad libitum water intake (all p > 0.05). Disinhibition is associated with higher thirst perception in healthy weight individuals and may be attenuated in obesity. The characteristics of disinhibition which typically includes a heightened readiness to eat, may reflect a more general phenotype that also reflects a readiness to drink.

Reproducibility and determinants of the metabolic responses during a mixed-meal tolerance test

OBJECTIVE

The aim of this study was to assess the reproducibility and physiological determinants of mixed-meal tolerance tests (MMTTs) on glucose and insulin responses.

METHODS

While inpatients on a weight-maintaining diet, 894 individuals (574 with normal and 267 with impaired glucose regulation and 53 with type 2 diabetes [T2D]) underwent 9-hour MMTTs (breakfast and lunch; 30% weight-maintaining diet each; 40% carbohydrate, 40% fat, and 20% protein). Total/incremental areas under the curve (AUC/iAUC) were calculated from MMTT plasma glucose/insulin concentrations. Acute insulin response (AIR) was quantified by intravenous glucose tolerance test and insulin action (M) via hyperinsulinemic-euglycemic clamp. A subset had repeat MMTTs (median follow-up = 1.4 years).

RESULTS

In individuals without T2D, for breakfast-versus-lunch reproducibility of glucose, AUCs were moderate (intraclass correlation coefficients [ICCs]: 0.44-0.61), and iAUCs were poor (ICCs < 0.15). For repeated MMTTs, reproducibility of AUC/iAUCs was low (ICCs: 0.11-0.36). For insulin, AUC reproducibility was high (ICCs > 0.70), and iAUCs were moderate (ICCs: 0.64-0.71). For repeated MMTTs, ICC AUC/iAUCs were 0.34 to 0.54. In those with T2D, ICC glucose AUC/iAUCs were >0.80 and >0.50, respectively, and for insulin were <0.40. For repeated MMTTs, ICC glucose/insulin AUC/iAUCs were moderate. Glucose AUCs associated with M/AIR (partial Rs < -0.25), and insulin AUCs negatively/positively associated with M/AIR (partial Rs = -0.51/0.24).

CONCLUSIONS

Reproducibility of glucose/insulin responses to MMTTs varied by subtraction of fasting values, glucose status, and time. Insulin secretion and action explained ~20% of MMTT responses. The substantial variability in MMTT response requires consideration in studies using MMTT outcomes.

Improved food Go/No-Go scores after transcranial direct current stimulation (tDCS) to prefrontal cortex in a randomized trial

OBJECTIVE

Reduced dorsolateral prefrontal cortex (dlPFC) activity and inhibitory control may contribute to obesity. The study objective was to assess effects of repeated transcranial direct current stimulation (tDCS) on food Go/No-Go (GNG), food Stroop performance, and snack food intake.

METHODS

Twenty-nine individuals with obesity (12 male; mean [SD], age 42 [11] years; BMI 39 [8]) participated in a combined inpatient/outpatient randomized parallel-design trial and received 15 sessions of anodal or sham tDCS to the left dlPFC. Food-related inhibitory control (GNG), attentional bias (Stroop), and snack food intake were assessed at baseline, completion of inpatient sessions (day 7), and follow-up (day 31).

RESULTS

GNG performance improved in the anodal group by day 31, compared with sham (p = 0.01), but Stroop scores did not differ by intervention. Greater snack food intake was associated with lower GNG scores (p = 0.01), driven by the sham group (p < 0.001) and higher food and palatable bias scores on the Stroop (all p = 0.02) across both groups. Changes on tasks were not associated with changes in intake.

CONCLUSIONS

Anodal tDCS to the left dlPFC improved performance on a food-related inhibitory control task, providing evidence of potential for therapeutic benefit of neuromodulation in areas controlling executive function. Results showed that tDCS to the dlPFC reduced snack food intake and hunger; however, underlying neurocognitive mechanisms remain uncertain.

Energy expenditure measurements are reproducible in different whole-room indirect calorimeters in humans

OBJECTIVE

This study aimed to evaluate the agreement of commonly reported energy metabolism measurements obtained from two different whole-room indirect calorimeters (WRICs).

METHODS

Nine healthy adult volunteers were evaluated over four separate 24-hour periods in a crossover design, twice in two different WRICs of different sizes, each operated according to the Room Indirect Calorimetry Operating and Reporting Standards published in 2020. The reproducibility of repeated measurements was quantified by the coefficient of variation (CV) and intraclass correlation coefficient (ICC).

RESULTS

The CVs between and within each WRIC for average 24-hour carbon dioxide production rate (VCO₂ ) and oxygen consumption rate (VO₂ ), 24-hour energy expenditure (EE), and respiratory exchange ratio ranged from 1.5% to 3.6%, whereas sleep EE ranged from 3.1% to 5.5%. CVs for macronutrient oxidation rates and spontaneous physical activity were higher, ranging from 9.2% to 38.1%. ICCs of VCO₂ , VO₂ , 24-hour EE, and energy expenditure at zero activity were >0.95, indicating excellent reproducibility, whereas ICCs for lipid oxidation, awake and fed thermogenesis, and sleep EE ranged from 0.55 to 0.92, indicating moderate to high reproducibility. ICCs for respiratory exchange ratio and carbohydrate and protein oxidation rates were lower (<0.70). Spontaneous physical activity showed high reproducibility within chambers (ICC = 0.88) but differed substantially between chambers (ICC = 0.23).

CONCLUSIONS

Cross-chamber reproducibility is high for common outcome measures assessed in the respiratory chamber. The results support efforts to promote standardization across WRICs to allow multicenter studies.

Water intake, thirst, and copeptin responses to two dehydrating stimuli in lean men and men with obesity

OBJECTIVE

Physiological systems responsible for water homeostasis and energy metabolism are interconnected. This study hypothesized altered responses to dehydration including thirst, ad libitum water intake, and copeptin in men with obesity.

METHODS

Forty-two men (22 lean and 20 with obesity) were stimulated by a 2-hour hypertonic saline infusion and a 24-hour water deprivation. In each dehydrating condition, thirst, ad libitum water intake after dehydration, and urinary and hormonal responses including copeptin were assessed.

RESULTS

After each dehydration condition, ad libitum water intake was similar between both groups (p > 0.05); however, those with obesity reported feeling less thirsty (p < 0.05) and had decreased copeptin response and higher urinary sodium concentrations when stressed (p < 0.05). Angiotensin II, aldosterone, atrial and brain natriuretic peptides, and apelin concentrations did not differ by adiposity group and did not explain the different thirst or copeptin responses in men with obesity. However, leptin was associated with copeptin response in lean individuals during the hypertonic saline infusion (p < 0.05), but the relationship was diminished in those with obesity.

CONCLUSIONS

Diminished thirst and copeptin responses are part of the obesity phenotype and may be influenced by leptin. Adiposity may impact pathways regulating thirst and vasopressin release, warranting further investigation.

Food insecurity is associated with higher respiratory quotient and lower glucagon-like peptide 1

OBJECTIVE

Food insecurity is known to be associated with obesity, but its association with physiological measures is unclear. Therefore, it was hypothesized that, compared with food-secure individuals, those with food insecurity would have higher 24-hour energy expenditure (EE [kilocalories per day]) and 24-hour respiratory quotient (RQ [ratio]). Subsequently, hormones involved in appetite regulation, substrate oxidation, and EE were explored.

METHODS

A total of 113 healthy participants without diabetes (75 men; mean [SD], age 40 [12] years; BMI 30 [8] kg/m² ) were included in this analysis. Participants completed the Food Security Short Form, underwent a dual-energy x-ray absorptiometry scan, and spent 24 hours in a human respiratory chamber following a weight-maintaining diet.

RESULTS

Compared with individuals with food security, participants with food insecurity had no difference in 24-hour EE. However, they had higher carbohydrate oxidation rates (p = 0.03) and lower lipid oxidation rates (p = 0.02), resulting in higher 24-hour RQ (p < 0.01). They also had lower fasting glucagon-like peptide 1 (p = 0.03) concentrations.

CONCLUSIONS

Food insecurity is associated with higher 24-hour RQ and lower fasting glucagon-like peptide 1 concentrations, metabolic and hormonal differences previously shown to drive greater calorie intake in the setting of unrestricted food availability. These findings therefore provide new insight into the paradoxical link between restricted food access and increased adiposity.

Trends in spontaneous physical activity and energy expenditure among adults in a respiratory chamber, 1985 to 2005

OBJECTIVE

Fidgeting, a type of spontaneous physical activity (SPA), has substantial thermogenic potential. This research aims to examine secular trends in SPA and energy expenditure (EE) inside a respiratory chamber.

METHODS

From 1985 to 2005, healthy adults (n = 678; mean age: 28.8 years; men: 60%; 522 Indigenous American, 129 White, and 27 Black) had a 24-hour stay in the respiratory chamber equipped with radar sensors. Body composition, glucose tolerance, fasting insulin, insulin action (hyperinsulinemic-euglycemic clamp), and insulin secretion (intravenous glucose tolerance test) were measured as covariates.

RESULTS

SPA, adjusted for age, sex, race, and body composition, declined (r = -0.30, p < 0.0001), with a concomitant rise in the energy cost of SPA (r = 0.30, p < 0.0001). The 24-hour EE adjusted for covariates increased (r = 0.31, p < 0.0001), which was reflected in increases in EE during sleep (r = 0.18, p < 0.0001) and during the awake, fed condition (r = 0.28, p < 0.0001). The secular trends in SPA or 24-hour EE were unchanged with adjustment for measures related to glucose metabolism.

CONCLUSIONS

Secular trend analyses showed a decline in fidgeting. However, this decline in SPA was partially counterbalanced by an increase in energy cost of this activity and a rise in EE. Nevertheless, our results support public health efforts to promote small but sustained changes in these behaviors.

Food insecurity moderates the relationship between momentary affect and adherence in a dietary intervention study

OBJECTIVE

Negative affect and food insecurity have been proposed to impede adherence to weight loss interventions. Therefore, this study examined the role of these variables on dietary adherence using Ecological Momentary Assessment.

METHODS

A total of 50 participants (19 male participants; age = 49 [SD 14] years) participated in an outpatient dietary study. Lean participants (n = 22; BMI ≤ 25 kg/m² ) received a weight-maintaining energy needs (WMEN) diet, and participants with obesity (BMI ≥ 30) were randomized to receive either a WMEN diet (n = 14) or a 35% calorie-reduced diet (n = 14). Food insecurity was measured, and, twice daily, Ecological Momentary Assessment captured real-time affect ratings and adherence. Between-person (trait-level) and lagged within-person (state-level) scores were calculated.

RESULTS

Greater food insecurity and trait-level negative affect were associated with reduced adherence (p = 0.0015, p = 0.0002, respectively), whereas higher trait-level positive affect was associated with greater adherence (p < 0.0001). Significant interactions between affect and food insecurity revealed an association between higher trait positive affect and increased adherence at lower levels of food insecurity. Higher trait negative affect was more strongly associated with decreased adherence in participants with greater levels of food insecurity (-1 SD: B = -0.21, p = 0.22; mean: B = -0.46, SE = 0.13, p = 0.0004; +1 SD: B = -0.71, SE = 0.17, p < 0.0001).

CONCLUSIONS

Trait-level affect may be crucial in predicting dietary adherence, especially in those with greater food insecurity.

Is Dietary Nonadherence Unique to Obesity and Weight Loss? Results From a Randomized Clinical Trial

OBJECTIVE

Weight stigma is associated with poor dietary adherence, yet adherence is essential for weight loss and maintenance. This study aimed to determine differences in dietary adherence and perceived hunger between lean individuals and two groups of individuals with obesity.

METHODS

In a 6-week outpatient dietary intervention (23 males; aged 48  [SD 14] years), lean participants (n = 23; BMI 23  [SD 2] kg/m² ) received a weight-maintaining energy needs (WMEN) diet, and participants with obesity (BMI 36  [SD 7]) were randomized to either WMEN (n = 18) or a 35% calorie-reduced (CR) diet (n = 19). All food was provided, and multiple adherence and hunger ratings were assessed daily and weekly on an outpatient basis and in person at twice-weekly visits (e.g., 24-hour recall, diaries).

RESULTS

Weight decreased more in the group of CR individuals with obesity (β = -0.301 kg/wk, P = 0.02) compared with the group of lean individuals and the group of WMEN individuals with obesity. However, total percent adherence did not differ between groups (P = 0.60), and hunger scores did not change across groups over time (P = 0.08).

CONCLUSIONS

Results indicate that there are no differences in dietary adherence between lean individuals and individuals with obesity and adherence is not associated with adiposity or hunger. Thus, the belief that nonadherence (e.g., lack of willpower) is unique to obesity is untrue and may perpetuate weight bias and stigma.

Assessing established BMI variants for a role in nighttime eating behavior in robustly phenotyped Southwestern American Indians

BACKGROUND/OBJECTIVES

Nighttime eating (NE) behavior has a genetic component and predicts weight gain. We hypothesized that some genetic variants, which affect NE would also show an effect on body mass index (BMI). We aimed to determine which known BMI variants associate with NE in Southwestern American Indians (SWAIs), who are at elevated risk for obesity.

METHODS

Known BMI variants from the GIANT-UK Biobank meta-analysis (N = 700,000) were analysed in SWAIs characterized for NE during an inpatient 3-day protocol. Variants were analysed for association with NE using whole-genome sequence data from 50 SWAIs (23 cases and 27 controls) and selected variants were genotyped in an additional 32 SWAIs (13 NE cases and 19 controls). Variants associated with NE in a meta-analysis of the two SWAI samples were further analysed for association with nightly caloric intake and functionality in hypothalamus, pituitary, and adrenal tissues.

RESULTS

Variants were identified where the allele that associated with increased BMI in the GIANT-UK Biobank meta-analysis (P ≤ 1 × 10^-8) also had a P < 0.01 for increased NE in the SWAI meta-analysis. These variants were captured by six tagSNPs. Comparison of the nightly calorie intake by genotype and eQTL data from relevant tissues highlighted rs3753612 upstream of HCRTR1.

CONCLUSIONS

Our strategy led to the HCRTR1 locus, which has previously been linked to sleep regulation and feeding. Although this is an intriguing candidate gene for NE, further studies in larger samples and different populations are required to validate the role of HCRTR1 in NE.

Brain Stimulation to Modulate Food Intake and Eating Behavior

PURPOSE OF REVIEW

Appetitive behaviors are mediated through homeostatic and reward signaling of brain circuits. There has been increasing interest in the use of neuromodulation techniques aimed at targeting brain regions such as the lateral prefrontal and subcortical regions associated with dysregulation of eating behaviors.

RECENT FINDINGS

Invasive brain stimulation techniques have demonstrated promising results in treating severe and enduring anorexia nervosa and morbid obesity. In addition, non-invasive techniques have been shown to successfully reduce food craving, hunger ratings, and calorie intake as well as binge/purge symptoms in eating disorders. Brain stimulation offers promising results for treating symptoms associated with eating disorders and modifying appetitive behaviors including craving and caloric consumption. Future research should focus on identifying optimal frequency and duration of stimulation and employ longitudinal studies to assess long-term effectiveness on clinical outcomes such as eating disorder symptomatology, weight loss, and sustained improvements in eating behaviors over time.

Fasting glucagon-like peptide 1 concentration is associated with lower carbohydrate intake and increases with overeating

PURPOSE

Glucagon-like peptide 1 (GLP-1) is an incretin hormone that appears to play a major role in the control of food intake. The aim of this investigation was to evaluate and quantify the association of circulating GLP-1 concentration with ad libitum total calorie and macronutrient intake.

METHODS

One-hundred and fifteen individuals (72 men) aged 35 ± 10 years were admitted for an inpatient study investigating the determinants of energy intake. Ad libitum food intake was assessed during 3 days using a reproducible vending machine paradigm. Fasting plasma GLP-1 concentrations were measured on the morning of the first day and on the morning of the fourth day after ad libitum feeding.

RESULTS

Plasma GLP-1 concentrations increased by 14% after 3 days of ad libitum food intake. Individuals overate on average 139 ± 45% of weight-maintaining energy needs. Fasting plasma GLP-1 on day 1 was negatively associated with carbohydrate intake (r = - 0.2, p = 0.03) and with daily energy intake from low fat-high simple sugar (r = - 0.22, p = 0.016).

CONCLUSION

Higher plasma GLP-1 concentrations prior to ad libitum food intake were associated with lower carbohydrate intake and lower simple sugar ingestion, indicating a possible role of the GLP-1 in the reward pathway regulating simple sugar intake.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00342732.

Food Insecurity is Associated with Maladaptive Eating Behaviors and Objectively Measured Overeating

OBJECTIVE

The association between food insecurity and obesity may be partially explained by overeating in response to unpredictable food availability cycles. The aim of this study was to measure objective food intake in food-insecure individuals.

METHODS

Eighty-two volunteers (53 m; BMI 29 ± 7; 38 ± 12 years) were admitted to our inpatient Clinical Research Unit and completed the Food Security Short Form, Three-Factor Eating Questionnaire, Gormally Binge Eating Scale, and body composition assessment (dual-energy x-ray absorptiometry). After 5 days of a weight-maintaining diet, participants self-selected food from an ad libitum vending machine paradigm for 3 days. Mean daily intake (kilocalories), macronutrient intake, and percentage of weight-maintaining energy needs (%WMEN) were calculated.

RESULTS

Based on Food Security Short Form cutoffs, food-insecure participants (n = 46; 56%) had higher body weight (P = 0.04), fat-free mass (P = 0.05), disinhibition (P = 0.008), hunger (P = 0.02), and binge-eating scores (P = 0.02) but not cognitive restraint (P = 0.37) compared with food-secure individuals. They overate more kilocalories (P = 0.001), %WMEN (P = 0.003), fat (P = 0.003), and carbohydrates (P = 0.004) during the vending machine paradigm, continued to increase their hourly rate of kilocalories (group × time; β = 37.7 cumulative kcal/h; P < 0.0001), and ate more total kilocalories across the 72 hours (β = 47.09 kcal/h; P = 0.003).

CONCLUSIONS

Food insecurity may amplify susceptibility to weight gain via overeating during times of unlimited food access.

The association between program credibility, expectancy, and acceptability with baseline pathology and outcome for a body acceptance prevention program

OBJECTIVE

The current study sought to investigate whether credibility, expectancy, and acceptability of the Body Project is impacted by level of disordered eating pathology and whether perceived credibility, expectancy, and acceptability impacts treatment outcomes.

METHODS

The sample included 170 undergraduate women from a large public university. Participants completed self-report questionnaires on perceived credibility, expectancy, treatment acceptability, and disordered eating measures. A random subset of 51 participants provided 3-month follow-up measurements.

RESULTS

Analyses revealed that post-prevention credibility, expectancy, and treatment acceptability scores were negatively associated with baseline thin-ideal internalization, baseline weight, and shape concerns, and positively associated with baseline body satisfaction and the baseline restraint subscale of the EDEQ. Perceived credibility, expectancy, and treatment acceptability were not associated with session attendance or 3-month follow-up disordered eating scores.

DISCUSSION

The Body Project is effective at reducing disordered eating regardless of whether participants liked the program or not.

High Fat and Sugar Consumption During Ad Libitum Intake Predicts Weight Gain

OBJECTIVE

To determine how macronutrients accompanying foods with high energy density (EnDen) affect energy intake and weight gain.

METHODS

A total of 214 subjects (130 males, BMI: 32 ± 7 kg/m² ) ate ad libitum for 3 days. Food intake was expressed as the mean daily intake (in kilocalories) and the percentage of weight-maintaining energy needs (%WMEN). EnDen was expressed as the ratio of intake (in kilocalories) to food weight (in grams). Food choices were expressed as absolute and percent intake (kilocalories), categorized as high in fat (HF; ≥ 45% kcal) or low in fat (LF; < 20% kcal), and further categorized as high in complex carbohydrates (≥ 30% kcal), high in simple sugars (HSS; ≥ 30% kcal), or high in protein (HP; ≥ 13% kcal). Follow-up weights were available from 99 subjects (65 males, range: 6 months to 11 years).

RESULTS

EnDen was associated with BMI (r = 0.28, P < 0.0001), percent body fat (r = 0.18, P = 0.007), and percent intake from HF/HP (r = 0.34, P < 0.0001), HF/HSS (r = 0.31, P < 0.0001), LF/HP (r = -0.37, P < 0.0001) and LF/HSS (r = -0.68, P < 0.0001). The %WMEN was associated with EnDen (r = 0.16, P = 0.01), HF/HSS (r = 0.33, P < 0.0001), and LF/HP intake (r = -0.25, P = 0.0002). In a multivariate model, only HF/HSS intake remained a significant predictor of %WMEN (β = 1.4% per 1% change, P < 0.0001). The percent intake from HF/HSS (r = 0.23, P = 0.02), not EnDen (P = 0.54), was associated with weight gain, even after adjusting for follow-up time (in years) and covariates.

CONCLUSIONS

Relatively greater consumption of HF/HSS foods independently predicted overeating and weight gain. Nutrient compositions of high-EnDen foods may be important for weight management.

Obesity, Appetite, and the Prefrontal Cortex

PURPOSE OF REVIEW

Obesity is a chronic illness and its prevalence is growing worldwide and numerous factors play a role in the regulation of food intake. The prefrontal cortex (PFC) is involved in high-order executive function, regulation of limbic reward regions, and the inhibition of impulsive behaviors. Understanding the role of the PFC in the control of appetite regulation may contribute to a greater understanding of the etiology of obesity and could improve weight loss outcomes.

RECENT FINDINGS

Neuroimaging studies have identified lower activation in the left dorsolateral PFC (DLPFC) in obese compared to lean individuals and others have focused on efforts to improve cognitive control in this area of the brain. The DLPFC is a critical brain area associated with appetitive control, food craving, and executive functioning, indicating a candidate target area for treatment. Further studies are needed to advance our understanding of the relationship between obesity, appetite, and the DLPFC and provide validation for the effectiveness of novel treatments in clinical populations.

Neuromodulation directed at the prefrontal cortex of subjects with obesity reduces snack food intake and hunger in a randomized trial

Background: Obesity is associated with reduced activation in the left dorsolateral prefrontal cortex (DLPFC), a region of the brain that plays a key role in the support of self-regulatory aspects of eating behavior and inhibitory control. Transcranial direct current stimulation (tDCS) is a noninvasive technique used to modulate brain activity.Objectives: We tested whether repeated anodal tDCS targeted at the left DLPFC (compared with sham tDCS) has an immediate effect on eating behavior during ad libitum food intake, resulting in weight change, and whether it might influence longer-term food intake-related appetite ratings in individuals with obesity.Design: In a randomized parallel-design study combining inpatient and outpatient assessments over 31 d, 23 individuals with obesity [12 men; mean ± SD body mass index (BMI; in kg/m²): 39.3 ± 8.42] received 15 sessions of anodal (i.e., enhancing cortical activity) or sham tDCS aimed at the left DLPFC. Ad libitum food intake was assessed through the use of a vending machine paradigm and snack food taste tests (SFTTs). Appetite was evaluated with a visual analog scale (VAS). Body weight was measured. We examined the effect of short-term (i.e., 3 sessions) and long-term (i.e., 15 sessions) tDCS on these variables.Results: Relative to sham tDCS, short-term anodal tDCS did not influence ad libitum intake of food from the vending machines. Accordingly, no effect on short-term or 4-wk weight change was observed. In the anodal tDCS group, compared with the sham group, VAS ratings for hunger and the urge to eat declined significantly more (P = 0.01 and P = 0.05, respectively), and total energy intake during an SFTT was relatively lower in satiated individuals (P = 0.01), after long-term tDCS.Conclusions: Short-term anodal tDCS of the left DLPFC did not have an immediate effect on ad libitum food intake or thereby weight change, relative to sham tDCS. Hunger and snack food intake were reduced only after a longer period of anodal tDCS in individuals with obesity. This trial was registered at clinicaltrials.gov as NCT00739362.