Interindividual variability in appetitive sensations and relationships between appetitive sensations and energy intake

BACKGROUND

Appetitive sensations (AS) are signals that guide eating behaviors. Marked short-term inter-individual variability in AS has been reported but the long-term stability of individual ratings and their dietary implications are not well characterized.

OBJECTIVES

This study explored the stability of inter-individual ratings of hunger, fullness and thirst for 17 weeks; determined the relationships between these sensations, eating patterns and energy intake (EI); as well as the associations between ratings and selected individual characteristics (age, gender, BMI).

METHODS

A 17-week observational study collected hourly appetitive ratings and dietary intake data from 97 (90 completers, 7 partial completers) healthy adults at weeks 1, 9, and 17.

RESULTS

There were marked and stable inter-individual differences over the 17 weeks for hunger (week 1 vs. week 9, r = 0.72 (p < 0.001); week 1 vs. week 17, r = 0.67 (p < 0.001); week 9 vs. week 17, r = 0.77 (p < 0.001)); fullness (week 1 vs. week 9 r = 0.74 (p < 0.001); week 1 vs. week 17, r = 0.71 (p < 0.001); week 9 vs. week 17, r = 0.81 (p < 0.001)); and thirst (week 1 vs. week 9 r = 0.82 (p < 0.001); week 1 vs. week 17, r = 0.81 (p < 0.001); week 9 vs. week 17, r = 0.88 (p < 0.001)). Cross-correlation functions revealed EI and eating pattern exerted stronger effects on AS than the reverse. However, the absolute effect sizes were small. Path analyses also indicated that there were weak relationships between AS and EI. No robust effects of the studied individual characteristics were observed.

CONCLUSION

This study found that acute and chronic sensations of hunger, fullness and thirst are relatively stable within individuals but vary markedly between individuals. In addition, the present data indicate AS are poorly associated with dietary patterns or with EI under conditions of relatively stable energy balance.

Perspective: A Research Roadmap about Ultra-Processed Foods and Human Health for the United States Food System: Proceedings from an Interdisciplinary, Multi-Stakeholder Workshop

Our objective was to convene interdisciplinary experts from government, academia, and industry to develop a Research Roadmap to identify research priorities about processed food intake and risk for obesity and cardiometabolic diseases (CMD) among United States populations. We convened attendees at various career stages with diverse viewpoints in the field. We held a "Food Processing Primer" to build foundational knowledge of how and why foods are processed, followed by presentations about how processed foods may affect energy intake, obesity, and CMD risk. Breakout groups discussed potential mechanistic and confounding explanations for associations between processed foods and obesity and CMD risk. Facilitators created research questions (RQs) based on key themes from discussions. Different breakout groups convened to discuss what is known and unknown for each RQ and to develop sub-RQs to address gaps. Workshop attendees focused on ultra-processed foods (UPFs; Nova Group 4) because the preponderance of evidence is based on this classification system. Yet, heterogeneity and subjectivity in UPF classification was a challenge for RQ development. The 6 RQs were: 1) What objective methods or measures could further categorize UPFs, considering food processing, formulation, and the interaction of the two? 2) How can exposure assessment of UPF intake be improved? 3) Does UPF intake influence risk for obesity or CMDs, independent of diet quality? 4) What, if any, attributes of UPFs influence ingestive behavior and contribute to excess energy intake? 5) What, if any, attributes of UPFs contribute to clinically meaningful metabolic responses? 6) What, if any, external environmental factors lead people to consume high amounts of UPFs? Uncertainty and complexity around UPF intake warrant further complementary and interdisciplinary causal, mechanistic, and methodological research related to obesity and CMD risk to understand the utility of applying classification by degree of processing to foods in the United States.

Ultraprocessed Foods and Obesity Risk: A Critical Review of Reported Mechanisms

Epidemiologic evidence supports a positive association between ultraprocessed food (UPF) consumption and body mass index. This has led to recommendations to avoid UPFs despite very limited evidence establishing causality. Many mechanisms have been proposed, and this review critically aimed to evaluate selected possibilities for specificity, clarity, and consistency related to food choice (i.e., low cost, shelf-life, food packaging, hyperpalatability, and stimulation of hunger/suppression of fullness); food composition (i.e., macronutrients, food texture, added sugar, fat and salt, energy density, low-calorie sweeteners, and additives); and digestive processes (i.e., oral processing/eating rate, gastric emptying time, gastrointestinal transit time, and microbiome). For some purported mechanisms (e.g., fiber content, texture, gastric emptying, and intestinal transit time), data directly contrasting the effects of UPF and non-UPF intake on the indices of appetite, food intake, and adiposity are available and do not support a unique contribution of UPFs. In other instances, data are not available (e.g., microbiome and food additives) or are insufficient (e.g., packaging, food cost, shelf-life, macronutrient intake, and appetite stimulation) to judge the benefits versus the risks of UPF avoidance. There are yet other evoked mechanisms in which the preponderance of evidence indicates ingredients in UPFs actually moderate body weight (e.g., low-calorie sweetener use for weight management; beverage consumption as it dilutes energy density; and higher fat content because it reduces glycemic responses). Because avoidance of UPFs holds potential adverse effects (e.g., reduced diet quality, increased risk of food poisoning, and food wastage), it is imprudent to make recommendations regarding their role in diets before causality and plausible mechanisms have been verified.

Effect of almond consumption on insulin sensitivity and serum lipids among Asian Indian adults with overweight and obesity- A randomized controlled trial

Background

Asian Indians have an increased susceptibility to type 2 diabetes and premature coronary artery disease. Nuts, like almonds, are rich in unsaturated fat and micronutrients with known health benefits.

Objectives

This study aimed to assess the efficacy of almonds for reduction of insulin resistance and improving lipid profile in overweight Asian Indian adults.

Methods

This parallel-arm, randomized, controlled trial was conducted in Chennai, India on 400 participants aged 25-65 years with a body mass index ≥ 23 kg/m². The intervention group received 43 g of almonds/day for 12 weeks, while the control group was advised to consume a customary diet but to avoid nuts. Anthropometric, clinical, and dietary data were assessed at periodic intervals. Glucose tolerance, serum insulin, glycated hemoglobin, C-peptide and lipid profile were assessed at baseline and end of the study. Insulin resistance (homeostasis assessment model-HOMA IR) and oral insulin disposition index (DIo) were calculated.

Results

A total of 352 participants completed the study. Significant improvement was seen in DIo [mean (95% CI) = + 0.7 mmol/L (0.1, 1.3); p = 0.03], HOMA IR (-0.4 (-0.7, -0.04; p = 0.03) and total cholesterol (-5.4 mg/dl (-10.2, -0.6); p = 0.03) in the intervention group compared to the control group. Incremental area under the curve (IAUC) and mean amplitude of glycemic excursion (MAGE) assessed using continuous glucose monitoring systems were also significantly lower in the intervention group. Dietary 24-h recalls showed a higher significant reduction in carbohydrate and increase in mono unsaturated fatty acid (MUFA) and polyunsaturated fatty acids (PUFA) intake in the intervention group compared to the control group.

Conclusion

Daily consumption of almonds increased the intake of MUFA with decrease in carbohydrate calories and decreases insulin resistance, improves insulin sensitivity and lowers serum cholesterol in Asian Indians with overweight/obesity. These effects in the long run could aid in reducing the risk of diabetes and other cardiometabolic disease.

Frequency of Eating in the US Population: A Narrative Review of the 2020 Dietary Guidelines Advisory Committee Report

Background

A person's daily nutrient intake and overall nutritional status are determined by a complex interplay of the types and amounts of foods ingested in combination with the timing and frequency of eating.

Objectives

The aim was to summarize frequency of eating occasion data examined by the 2020 Dietary Guidelines Advisory Committee, the macronutrient contributions they provide, and meal frequency relative to dietary quality among the US population (≥2 y), with a focus on sex, age, race/Hispanic origin, and income.

Methods

Demographic and 24-h recall data from the 2013-2016 NHANES were examined. An eating occasion was defined as "any ingestive event (e.g., solid food, beverage, water) that is either energy yielding or non-energy yielding"; all eating occasions were further divided into discrete meals and snacks. Frequency of meals and snacks was defined as "the number of daily EOs [eating occasions]," respectively. Diet quality was assessed via the Healthy Eating Index (HEI)-2015.

Results

Most Americans consume 2 (28%) to 3 (64%) meals on a given day and >90% consume 2 to 3 snacks on that day. Adult, Hispanic, and non-Hispanic Black and lower-income (<131% family poverty-to-income ratio) Americans had a lower frequency of eating than children or adolescents, non-Hispanic White, and non-Hispanic Asian Americans and higher-income Americans, respectively. Americans who reported 3 meals on a given day consumed a diet higher in dietary quality than Americans who consumed 2 meals on a given day (HEI-2015: 61.0 vs. 55.0), regardless of population subgroup.

Conclusions

The frequency of the types of eating occasions differs according to age, race and Hispanic origin, and income. Dietary quality is associated with the number of meals consumed. Healthy dietary patterns can be constructed in a variety of ways to suit different life stages, cultural practices, and income levels; improved diet quality and careful consideration of nutrient density when planning meals are warranted.

Valuing the Diversity of Research Methods to Advance Nutrition Science

The ASN Board of Directors appointed the Nutrition Research Task Force to develop a report on scientific methods used in nutrition science to advance discovery, interpretation, and application of knowledge in the field. The genesis of this report was growing concern about the tone of discourse among nutrition professionals and the implications of acrimony on the productive study and translation of nutrition science. Too often, honest differences of opinion are cast as conflicts instead of areas of needed collaboration. Recognition of the value (and limitations) of contributions from well-executed nutrition science derived from the various approaches used in the discipline, as well as appreciation of how their layering will yield the strongest evidence base, will provide a basis for greater productivity and impact. Greater collaborative efforts within the field of nutrition science will require an understanding that each method or approach has a place and function that should be valued and used together to create the nutrition evidence base. Precision nutrition was identified as an important emerging nutrition topic by the preponderance of task force members, and this theme was adopted for the report because it lent itself to integration of many approaches in nutrition science. Although the primary audience for this report is nutrition researchers and other nutrition professionals, a secondary aim is to develop a document useful for the various audiences that translate nutrition research, including journalists, clinicians, and policymakers. The intent is to promote accurate, transparent, verifiable evidence-based communication about nutrition science. This will facilitate reasoned interpretation and application of emerging findings and, thereby, improve understanding and trust in nutrition science and appropriate characterization, development, and adoption of recommendations.

No apparent effects of a viscous, superabsorbent hydrogel on appetite, energy intake, or fecal excretion in overweight adults

As the obesity epidemic continues, there is a great need for safe and effective weight loss aids. A superabsorbent hydrogel device administered as a capsule demonstrates potential for weight loss, but its mechanism of action remains unclear. The present study's goal was to determine the mechanisms of action of the hydrogel through the investigation of its effects on appetitive sensations, eating behavior, energy intake, and fecal excretion of energy. Overweight and obese adults (n = 18) participated in a double-blind, randomized, crossover-design study in which they were provided all meals for a week in a supervised setting (i.e., controlled-feeding) and were required to either consume the hydrogel or a placebo with 16-oz of water 20 min before lunch and dinner. No differences in appetite (all, p > 0.05), total fecal nitrogen excretion (p = 0.74), total fecal fat excretion (p = 0.54), or total fecal energy excretion (p = 0.76) were identified when comparing the hydrogel to a placebo. Affect towards food (i.e., mood, emotions) was more positive in the hydrogel group compared with the placebo group. A subset of the controlled-feeding group (n = 10) then participated in another double-blind, randomized, crossover-design study in which they provided their own food for a week (i.e., free-feeding) and were required to either consume the hydrogel or a placebo with 16-oz of water 20 min before lunch and dinner. No differences in appetite (all, p > 0.05), energy intake (p = 0.95), diet quality (all, p > 0.05), or eating behavior (all, p > 0.05) were determined when comparing the hydrogel to the placebo. Future studies with greater statistical power should confirm these findings and investigate other potential mechanisms of action of the hydrogel.

Finding the Sweet Spot: Measurement, Modification, and Application of Sweet Hedonics in Humans

Sweetness is a sensation that contributes to the palatability of foods, which is the primary driver of food choice. Thus, understanding how to measure the appeal (hedonics) of sweetness and how to modify it are key to effecting dietary change for health. Sweet hedonics is multidimensional so can only be captured by multiple approaches including assessment of elements such as liking, preference, and consumption intent. There are both innate and learned components to the appeal of sweet foods and beverages. These are responsive to various behavioral and biological factors, suggesting the opportunity to modify intake. Given the high amount of added sugar intake in the United States and recommendations from many groups to reduce this, further exploration of current hypothesized approaches to moderate sugar intake (e.g., induced hedonic shift, use of low-calorie sweeteners) is warranted.

Effects of Concord grape juice flavor intensity and phenolic compound content on glycemia, appetite and cognitive function in adults with excess body weight: a randomized double-blind crossover trial

Background & aims: Concord grape (Vitis lambrusca) juice (CGJ) contains a unique combination of polyphenolic compounds with diverse effects on human health. It also has an intense sensory profile that may modify food choice. Daily consumption of CGJ over 8 weeks reduced fasting blood glucose. However, the impact on 24h-postprandial glucose response from CGJ is still not clear. The purpose of this study was to assess the effect of CGJ flavor intensity and phenolic content on 24 h postprandial glucose concentrations, appetitive sensations, and cognitive function in adults with excess body weight when consumed alone or with a meal. Methods: In a randomized, double-blind, crossover design study, participants consumed three types of beverages: 100% CGJ, a polyphenol-free grape flavored drink with the same flavor essence (LP) or a polyphenol-free grape flavored drink with reduced flavor essence (LPF) either without (trial I) or with (trial II) a meal. 24 h glucose was measured through continuous glucose monitoring. Phenolic metabolite excretion was assessed in 24 h urine samples. Appetite (hunger, thirst, fullness, desire to eat, and prospective consumption) and cognitive function (alertness, energetic, strength, calmness, and relaxation) were assessed hourly through visual analog scales. Results: Thirty-four adults completed trial I and 34 adults completed trial II. When consumed with a meal, beverages with customary flavor essence (CGJ and LP) reduced hunger, desire to eat, and prospective consumption and consumption of the polyphenol-free reduced flavor essence beverage was associated with higher 24 h glucose _tAUC. No consistent effects were observed for cognitive outcomes. When consumed alone, CGJ was related to lower glycemic responses by those excreting a higher concentration of the phenolic metabolite iso/ferulic-3'-O-glucuronide, but in beverages without CG phenolics and reduced flavor essence, glycemia was higher among those excreting higher concentrations of caffeic acid-O-sulfate. Conclusions: Both natural phenolics and flavor essence of CGJ may help to moderate appetite and glycemia. Clinical Trials registered at http://www.clinicaltrials.gov: NCT03409484 (trial I) and NCT03409497 (trial II).

Systematic Review and Meta-Analysis on the Effect of Portion Size and Ingestive Frequency on Energy Intake and Body Weight among Adults in Randomized Controlled Feeding Trials

Energy intake is the product of portion size (PS)-the energy content of an ingestive event-and ingestive frequency (IF)-the number of ingestive events per unit time. An uncompensated alteration in either PS or IF would result in a change in energy intake and body weight if maintained over time. The objective of this meta-analysis was to assess the independent effects of PS and IF on energy intake and body weight among healthy adults in randomized controlled trials (RCTs). A total of 9708 articles were identified in PubMed, Web of Science, Cochrane, and CINAHL databases. The articles were divided among 10 researchers; each article was screened for eligibility by 2-3 independent reviewers. Exclusion criteria included: populations <19 y and >65 y, unhealthy populations (i.e. participants with an acute or chronic disease), assessments <24 h and <4 wk in duration for trials investigating energy intake or body weight, respectively. Controlled feeding trials (i.e. fixed energy intake) that manipulated IF and PS in the same study intervention (IF/PS) were evaluated separately and for the body weight outcome only. Twenty-two studies (IF = 4, PS = 14, IF/PS = 4) met the inclusion criteria. There was an insufficient number of studies to assess the effect of IF, PS, or IF/PS on body weight. There was heterogeneity in the effect sizes among all comparisons (I2 ≥75%). Consuming larger portion sizes was associated with higher daily energy intake [295 kcal (202, 388), n = 24; weighted mean differences (WMD) (95% CI), n = comparisons], and increased frequency of ingestive events was associated with higher energy intake [203 kcal (76, 330), n = 10]. Results from RCTs support that larger PS and greater IF are both associated with higher energy consumption. However, there is insufficient information to determine chronic effects on body weight. This protocol was registered at the International Prospective Register of Systematic Reviews (PROSPERO) as CRD42018104757.

Evaluation of Dietary Patterns and All-Cause Mortality: A Systematic Review

Importance

The 2020 Dietary Guidelines Advisory Committee conducted a systematic review of existing research on diet and health to inform the current Dietary Guidelines for Americans. The committee answered this public health question: what is the association between dietary patterns consumed and all-cause mortality (ACM)?

Objective

To ascertain the association between dietary patterns consumed and ACM.

Evidence Review

Guided by an analytical framework and predefined inclusion and exclusion criteria developed by the committee, the US Department of Agriculture's Nutrition Evidence Systematic Review (NESR) team searched PubMed, the Cochrane Central Register of Controlled Trials, and Embase and dual-screened the results to identify articles that were published between January 1, 2000, and October 4, 2019. These studies evaluated dietary patterns and ACM in participants aged 2 years and older. The NESR team extracted data from and assessed risk of bias in included studies. Committee members synthesized the evidence, developed conclusion statements, and graded the strength of the evidence supporting the conclusion statements.

Findings

A total of 1 randomized clinical trial and 152 observational studies were included in the review. Studies enrolled adults and older adults (aged 17-84 years at baseline) from 28 countries with high or very high Human Development Index; 53 studies originated from the US. Most studies were well designed, used rigorous methods, and had low or moderate risks of bias. Precision, directness, and generalizability were demonstrated across the body of evidence. Results across studies were highly consistent. Evidence suggested that dietary patterns in adults and older adults that involved higher consumption of vegetables, fruits, legumes, nuts, whole grains, unsaturated vegetable oils, fish, and lean meat or poultry (when meat was included) were associated with a decreased risk of ACM. These healthy patterns were also relatively low in red and processed meat, high-fat dairy, and refined carbohydrates or sweets. Some of these dietary patterns also included intake of alcoholic beverages in moderation. Results based on additional analyses with confounding factors generally confirmed the robustness of main findings.

Conclusions and Relevance

In this systematic review, consuming a nutrient-dense dietary pattern was associated with reduced risk of death from all causes.

Perceptual Quality of Nonesterified Fatty Acids Varies with Fatty Acid Chain Length

Nonesterified fatty acids (NEFA) are effective taste stimuli. The quality they impart has not been well characterized. Sourness, and "fattiness" have been reported, but an irritation component has also been described and how these transition with gradations of aliphatic chain length has not been systematically studied. This study examined intensity and quality ratings of NEFA ranging from C2 to C18. Oral sites and the time course of sensations were also monitored. Given all NEFA contain carboxylic acid moieties capable of donating hydrogen ions, the primary stimulus for sour taste, testing was conducted with and without sour adaptation to explore the contribution of sour taste across the range of NEFA. Short-chain NEFA (C2-C6) were rated as predominantly sour, and this was diminished in C2 and C4 by sour adaptation. Medium-chain NEFA (C8-C12) were rated as mainly irritating with long-chain NEFA (C18) described mostly as bitter. The latter may reflect the lack of "fatty" lexicon to describe the sensation. Short-chain NEFA were mostly localized to the anterior tongue and were of rapid onset. The sensation from medium-chain NEFA was attributed to the lateral tongue, whereas medium- and long-chain NEFA sensations were predominantly localized to the back of the tongue and throat and had a longer lag time. The findings indicate there is a systematic transition of NEFA taste quality and irritation with increments in chain length and this is consistent with multiple modes of transduction.

Perspective: US Documentation and Regulation of Human Nutrition Randomized Controlled Trials

Training to ensure good documentation practices and adherence to regulatory requirements in human nutrition randomized controlled trials has not been given sufficient attention. Furthermore, it is difficult to find this information conveniently organized or in a form relevant to nutrition protocols. Current gaps in training and research surveillance exist in clinical nutrition research because training modules emphasize drugs and devices, promote reliance on monitoring boards, and lack nutrition expertise on human nutrition research teams. Additionally, because eating is essential, ongoing, and highly individualized, it is difficult to distinguish risks associated with interventions from eating under free-living conditions. Controlled-feeding trials provide an option to gain more experimental control over food consumed, but at a price of less external validity, and may pose human behavior issues that are unrelated to the intervention. This paper covers many of the expected practices for documentation and regulation that may be encountered in planning and conducting nutrition intervention trials with examples and references that should be useful to clinical nutrition researchers, funders of research, and research institutions. Included are definitions and guidance on clinical nutrition research oversight (institutional review boards, data safety and monitoring boards, US FDA); participant safety; standard operating procedures; training of investigators, staff, and students; and local culture and reporting requirements relevant to diet-related clinical research conduct and documentation.

NIH Workshop Report: sensory nutrition and disease

In November 2019, the NIH held the "Sensory Nutrition and Disease" workshop to challenge multidisciplinary researchers working at the interface of sensory science, food science, psychology, neuroscience, nutrition, and health sciences to explore how chemosensation influences dietary choice and health. This report summarizes deliberations of the workshop, as well as follow-up discussion in the wake of the current pandemic. Three topics were addressed: A) the need to optimize human chemosensory testing and assessment, B) the plasticity of chemosensory systems, and C) the interplay of chemosensory signals, cognitive signals, dietary intake, and metabolism. Several ways to advance sensory nutrition research emerged from the workshop: 1) refining methods to measure chemosensation in large cohort studies and validating measures that reflect perception of complex chemosensations relevant to dietary choice; 2) characterizing interindividual differences in chemosensory function and how they affect ingestive behaviors, health, and disease risk; 3) defining circuit-level organization and function that link and interact with gustatory, olfactory, homeostatic, visceral, and cognitive systems; and 4) discovering new ligands for chemosensory receptors (e.g., those produced by the microbiome) and cataloging cell types expressing these receptors. Several of these priorities were made more urgent by the current pandemic because infection with sudden acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the ensuing coronavirus disease of 2019 has direct short- and perhaps long-term effects on flavor perception. There is increasing evidence of functional interactions between the chemosensory and nutritional sciences. Better characterization of this interface is expected to yield insights to promote health, mitigate disease risk, and guide nutrition policy.

Perspective: Measuring Sweetness in Foods, Beverages, and Diets: Toward Understanding the Role of Sweetness in Health

Various global public health agencies recommend minimizing exposure to sweet-tasting foods or beverages. The underlying rationale is that reducing exposure to the perception of sweet tastes, without regard to the source of sweetness, may reduce preferences for sweetness, added sugar intake, caloric intake, and body weight. However, the veracity of this sequence of outcomes has yet to be documented, as revealed by findings from recent systematic reviews on the topic. Efforts to examine and document the effects of sweetness exposure are needed to support evidence-based recommendations. They require a generally agreed-upon methodology for measuring sweetness in foods, beverages, and the overall diet. Although well-established sensory evaluation techniques exist for individual foods in laboratory settings, they are expensive and time-consuming, and agreement on the optimal approach for measuring the sweetness of the total diet is lacking. If such a measure could be developed, it would permit researchers to combine data from different studies and populations and facilitate the design and conduct of new studies to address unresolved research questions about dietary sweetness. This narrative review includes an overview of available sensory techniques, their strengths and limitations, recent efforts to measure the sweetness of foods and diets across countries and cultures, and a proposed future direction for improving methods for measuring sweetness toward developing the data required to support evidence-based recommendations around dietary sweetness.

Examination of different definitions of snacking frequency and associations with weight status among U.S. adults

Snacks, while widely consumed in the United States (U.S.), do not have a standard definition, complicating research to understand associations, if any, with weight status. Therefore, the purpose of this study was to examine the association between snacking frequency and weight status using various snacking definitions that exist in the scientific literature among U.S. adults (NHANES 2013–2016; ≥20y n = 9,711). Four event-based snacking definitions were operationalized including participant-defined snacks, eating events outside of meals, and operationally defined snacks based on absolute thresholds of energy consumed (>50 kcal). Weight status was examined using body mass index (BMI), waist circumference, and sagittal abdominal diameter risk. Logistic regression models examined snacking frequency and associations with weight status. Outcomes varied by the definition of a snack employed, but the majority of findings were null. Mean energy from snacks was significantly higher among women with obesity compared to women with normal weight when a snack was defined as any event outside of a typical mealtime (i.e. other than breakfast, lunch, dinner, super, brunch), regardless of whether or not it contributed ≥50 kcal. Further investigation into ingestive behaviors that may influence the relationship between snacking frequency and weight status is needed.

Low Calorie Sweeteners Differ in Their Physiological Effects in Humans

Low calorie sweeteners (LCS) are prevalent in the food supply for their primary functional property of providing sweetness with little or no energy. Though tested for safety individually, there has been extremely limited work on the efficacy of each LCS. It is commonly assumed all LCS act similarly in their behavioral and physiological effects. However, each LCS has its own chemical structure that influences its metabolism, making each LCS unique in its potential effects on body weight, energy intake, and appetite. LCS may have different behavioral and physiological effects mediated at the sweet taste receptor, in brain activation, with gut hormones, at the microbiota and on appetitive responses. Further elucidation of the unique effects of the different commercially available LCS may hold important implications for recommendations about their use for different health outcomes.

A randomized controlled trial contrasting the effects of 4 low-calorie sweeteners and sucrose on body weight in adults with overweight or obesity

BACKGROUND

Low-calorie sweeteners (LCSs) provide sweetness with little or no energy. However, each LCS's unique chemical structure has potential to elicit different sensory, physiological, and behavioral responses that affect body weight.

OBJECTIVE

The purpose of this trial was to compare the effects of consumption of 4 LCSs and sucrose on body weight, ingestive behaviors, and glucose tolerance over a 12-wk intervention in adults (18-60 y old) with overweight or obesity (body mass index 25-40 kg/m2).

METHODS

In a parallel-arm design, 154 participants were randomly assigned to consume 1.25-1.75 L of beverage sweetened with sucrose (n = 39), aspartame (n = 30), saccharin (n = 29), sucralose (n = 28), or rebaudioside A (rebA) (n = 28) daily for 12 wk. The beverages contained 400-560 kcal/d (sucrose treatments) or <5 kcal/d (LCS treatments). Anthropometric indexes, energy intake, energy expenditure, appetite, and glucose tolerance were measured at baseline. Body weight was measured every 2 wk with energy intake, expenditure, and appetite assessed every 4 wk. Twenty-four-hour urine collections were completed every 4 wk to determine study compliance via para-aminobenzoic acid excretion.

RESULTS

Of the participants enrolled in the trial, 123 completed the 12-wk intervention. Sucrose and saccharin consumption led to increased body weight across the 12-wk intervention (Δweight = +1.85 ± 0.36 kg and +1.18 ± 0.36 kg, respectively; P ≤ 0.02) and did not differ from each other. There was no significant change in body weight with consumption of the other LCS treatments compared with baseline, but change in body weight for sucralose was negative and significantly lower compared with all other LCSs at week 12 (weight difference ≥ 1.37 ± 0.52 kg, P ≤ 0.008). Energy intake decreased with sucralose consumption (P = 0.02) and ingestive frequency was lower for sucralose than for saccharin (P = 0.045). Glucose tolerance was not significantly affected by any of the sweetener treatments.

CONCLUSIONS

Sucrose and saccharin consumption significantly increase body weight compared with aspartame, rebA, and sucralose, whereas weight change was directionally negative and lower for sucralose compared with saccharin, aspartame, and rebA consumption. LCSs should be categorized as distinct entities because of their differing effects on body weight. This trial was registered at clinicaltrials.gov as NCT02928653.

Aspartame Consumption for 12 Weeks Does Not Affect Glycemia, Appetite, or Body Weight of Healthy, Lean Adults in a Randomized Controlled Trial

Background

Low-calorie sweeteners are often used to moderate energy intake and postprandial glycemia, but some evidence indicates that they may exacerbate these aims.

Objective

The trial's primary aim was to assess the effect of daily aspartame ingestion for 12 wk on glycemia. Effects on appetite and body weight were secondary aims.

Methods

One hundred lean [body mass index (kg/m2): 18-25] adults aged 18-60 y were randomly assigned to consume 0, 350, or 1050 mg aspartame/d (ASP groups) in a beverage for 12 wk in a parallel-arm design. At baseline, body weight and composition were determined, a 240-min oral-glucose-tolerance test (OGTT) was administered, and measurements were made of appetite and selected hormones. Participants also collected a 24-h urine sample. During the intervention, the 0-mg/d ASP group consumed capsules containing 680 mg dextrose and 80 mg para-amino benzoic acid. For the 350-mg/d ASP group, the beverage contained 350 mg aspartame and the 1050-mg/d ASP group consumed the same beverage plus capsules containing 680 mg dextrose and 700 mg aspartame. Body weight, blood pressure, heart rate, and waist circumference were measured weekly. At weeks 4, 8, and 12, participants collected 24-h urine samples and kept appetite logs. Baseline measurements were repeated at week 12.

Results

With the exception of the baseline OGTT glucose concentration at 60 min (and resulting area under the curve value), there were no group differences for glucose, insulin, resting leptin, glucagon-like peptide 1, or gastric inhibitory peptide at baseline or week 12. There also were no effects of aspartame ingestion on appetite, body weight, or body composition. Compliance with the beverage intervention was ∼95%.

Conclusions

Aspartame ingested at 2 doses for 12 wk had no effect on glycemia, appetite, or body weight among healthy, lean adults. These data do not support the view that aspartame is problematic for the management of glycemia, appetite, or body weight. This trial was registered at www.clinicaltrials.gov as NCT02999321.

Nutrition and taste and smell dysfunction

Food selection plays a pivotal role in maintaining adequate nutrient intake, thus elucidating drivers of food choice is a meaningful strategy to maintain health and manage disease. Taste and smell are key determinants of food choice and warrant careful consideration. In this review, we first discuss how sensory stimulation influences food selection and metabolism. We then review the evidence regarding the relationship between taste and smell dysfunction and food preferences and selection, with attention given to contexts of certain chronic diseases. We conclude with brief recommendations for the management of chemosensory disorders. While sensory abilities influence food selection, the effect of taste and smell dysfunction on long-term consumption patterns and health status must be considered in light of environment, exposure, and culture.

Taste Responses to Linoleic Acid: A Crowdsourced Population Study

Dietary fats serve multiple essential roles in human health but may also contribute to acute and chronic health complications. Thus, understanding mechanisms that influence fat ingestion are critical. All sensory systems may contribute relevant cues to fat detection, with the most recent evidence supporting a role for the sense of taste. Taste detection thresholds for fat vary markedly between individuals and responses are not normally distributed. Genetics may contribute to these observations. Using crowdsourced data obtained from families visiting the Denver Museum of Nature & Science, our objective was to estimate the heritability of fat taste (oleogustus). A pedigree analysis was conducted with 106 families (643 individuals) who rated the fat taste intensity of graded concentrations of linoleic acid (LA) embedded in taste strips. The findings estimate that 19% (P = 0.043) of the variability of taste response to LA relative to baseline is heritable at the highest concentration tested.

The cephalic phase insulin response to nutritive and low-calorie sweeteners in solid and beverage form

The purpose of the study was to examine the role of the cephalic phase insulin response (CPIR) following exposure to nutritive and low-calorie sweeteners in solid and beverage form in overweight and obese adults. In addition, the role of learning on the CPIR to nutritive and low-calorie sweetener exposure was tested. Sixty-four overweight and obese adults (age: 18-50years, BMI: 24-37kg/m², body fat percentage>25% for men and >32% for women) were sham-fed (at 2-minute intervals for 14min) a randomly assigned test load comprised of a nutritive (sucrose) or low-calorie sweetener (sucralose) in beverage or solid form in phase 1 of the study. A 2-3ml blood sample was collected before and 2, 6, 10, 14, 61, 91 and 121min after oral exposure for serum insulin and glucose analysis. During phase 2, participants underwent a 2-week training period to facilitate associative learning between the sensory properties of test loads and their post-ingestive effects. In phase 3, participants were retested for their cephalic phase responses as in phase 1. Participants were classified as responders if they demonstrated a positive insulin response (rise of serum insulin above baseline i.e. Δ insulin) 2min post-stimulus in phase 1. Among responders exposed to the same sweetener in Phases 1 and 3, the proportion of participants that displayed a rise of insulin with oral exposure to sucralose was significantly greater when the stimulus was in the solid form compared to the beverage form. Sucralose and sucrose exposure elicited similarly significant increases in serum insulin 2min after exposure and significant decreases after 2min in responders in both food forms. The solid food form elicited greater CPIR over 2, 6 and 10min than the beverage form. There was no effect of learning on insulin responses after training. The results indicate the presence of a significant CPIR in a subset of individuals with overweight or obesity after oral exposure to sucralose, especially when present in solid food form. Future studies must confirm the reliability of this response.

Multiple Reaction Monitoring Profiling to Assess Compliance with an Almond Consumption Intervention

Background: Almonds are extremely rich sources of lipids and flavonoids, and their consumption is associated with several health benefits. However, there are no analytical methods available to document compliance with prescribed or self-reported chronic almond consumption. Objective: The aim was to use an analytical approach that identifies metabolic profiles associated with long-term almond consumption to ascertain compliance with prescribed consumption. Methods: A multiple reaction monitoring (MRM)-profiling strategy was designed to isolate metabolic changes in erythrocytes after 12 wk of almond consumption. MRM-profiling data acquisition and analysis involve performing separate discovery and screening steps to detect molecular features related to metabolic changes between experimental groups. Samples used for this research were erythrocytes recovered at baseline, after 12 wk of almond consumption (W12-almond group), and after 12 wk of a nut-free diet (W12-control group). For the MRM-profiling discovery step, representative samples (pools) of erythrocytes from individuals of all groups were interrogated by precursor ion and neutral loss scan experiments on the basis of previous knowledge of chemical functional groups present in the samples. The outputs of the discovery phase were methods used for the MRM-profiling screening phase to interrogate individual samples on the basis of fast-MRM measurements. In addition, we screened the literature for flavonoids identified in almond skins and included them for individual sample screening. Results: Of the 254 m/z values monitored, 5 ratios and combinations of specific ions with receiver operating characteristic curve AUCs >0.89 provided a sensitivity of 74.2% and a specificity of 90% for blind samples presented in the model. Eight of the 31 participants (25.8%) in the W12-almond group and 3 of the 30 (10%) participants in the W12-control group were misclassified by all 5 ratios. Ratios and combinations of specific transitions were mainly related to membrane lipids. Conclusion: The misclassifications observed as a result of ratio performance evaluation may indicate noncompliance as supported by the dietary intake data. The parent trial was registered at www.clinicaltrials.gov as NCT02360787.

Comparisons of Fatty Acid Taste Detection Thresholds in People Who Are Lean vs. Overweight or Obese: A Systematic Review and Meta-Analysis

Given the increasing evidence that supports the ability of humans to taste non-esterified fatty acids (NEFA), recent studies have sought to determine if relationships exist between oral sensitivity to NEFA (measured as thresholds), food intake and obesity. Published findings suggest there is either no association or an inverse association. A systematic review and meta-analysis was conducted to determine if differences in fatty acid taste sensitivity or intensity ratings exist between individuals who are lean or obese. A total of 7 studies that reported measurement of taste sensations to non-esterified fatty acids by psychophysical methods (e.g.,studies using model systems rather than foods, detection thresholds as measured by a 3-alternative forced choice ascending methodology were included in the meta-analysis. Two other studies that measured intensity ratings to graded suprathreshold NEFA concentrations were evaluated qualitatively. No significant differences in fatty acid taste thresholds or intensity were observed. Thus, differences in fatty acid taste sensitivity do not appear to precede or result from obesity.

Almond Consumption during Energy Restriction Lowers Truncal Fat and Blood Pressure in Compliant Overweight or Obese Adults

BACKGROUND

The inclusion of almonds in an energy-restricted diet has been reported both to enhance or to have no effect on weight loss. Their effects specifically on visceral body fat stores during energy restriction have not been widely examined. In addition, almond consumption has been associated with reduced blood pressure (BP), but whether this is linked to or independent of changes in body composition has to our knowledge not been examined.

OBJECTIVE

We evaluated the effects of consuming almonds as part of an energy-restricted diet on body composition, specifically visceral adipose tissue (VAT) and BP, compared to a nut-free energy-restricted diet.

METHODS

A randomized controlled 12-wk clinical trial of 86 healthy adults [body mass index (in kg/m²): 25-40] was conducted. Participants were randomly assigned to 1 of 2 energy-restricted (500-kcal deficit/d) diets: an almond-enriched diet (AED) (15% energy from almonds) or a nut-free diet (NFD). A linear mixed-model analysis on primary outcomes such as body weight, body fat, VAT, and BP was performed on all participants [intention-to-treat (ITT) analysis] and compliant participants (complier analysis).

RESULTS

Body weight, truncal and total fat percentage, VAT, and systolic BP decreased after 12 wk of energy restriction in both the ITT and complier analyses (P < 0.05). The complier analysis (but not the ITT analysis) indicated a greater mean ± SEM reduction in truncal fat (AED: -1.21% ± 0.26%; NFD: -0.48% ± 0.24%; P = 0.025), total fat (AED: -1.79% ± 0.36%; NFD: -0.74% ± 0.33%; P = 0.035), and diastolic BP (AED: -2.71 ± 1.2 mm Hg; NFD: 0.815 ± 1.1 mm Hg; P = 0.029), and a greater tendency for VAT loss (AED: -8.19 ± 1.8 cm²; NFD: -3.99 ± 1.7 cm²; P = 0.09) over time in the AED group than the NFD group.

CONCLUSIONS

Moderate almond consumption by compliant overweight and obese individuals during energy restriction results in greater proportional reductions of truncal and total body fat as well as diastolic BP and hence may help to reduce metabolic disease risk in obesity. This trial was registered at clinicaltrials.gov as NCT02360787.

The Macronutrients, Appetite, and Energy Intake

Each of the macronutrients-carbohydrate, protein, and fat-has a unique set of properties that influences health, but all are a source of energy. The optimal balance of their contribution to the diet has been a long-standing matter of debate. Over the past half century, thinking has progressed regarding the mechanisms by which each macronutrient may contribute to energy balance. At the beginning of this period, metabolic signals that initiated eating events (i.e., determined eating frequency) were emphasized. This was followed by an orientation to gut endocrine signals that purportedly modulate the size of eating events (i.e., determined portion size). Most recently, research attention has been directed to the brain, where the reward signals elicited by the macronutrients are viewed as potentially problematic (e.g., contribute to disordered eating). At this point, the predictive power of the macronutrients for energy intake remains limited.

The Effects of Increased Protein Intake on Fullness: A Meta-Analysis and Its Limitations

BACKGROUND

Higher protein intake has been implicated in weight management because of its appetitive properties. However, the effects of protein intake on appetitive sensations such as fullness have not been systematically assessed. Meta-analysis is a useful technique to evaluate evidence of an intervention's effect on testable outcomes, but it also has important limitations.

OBJECTIVE

The primary aim of this study was to synthesize the available evidence on the effect of protein intake on fullness using a quantitative meta-analysis and a secondary directional analysis using the vote-counting procedure. A tertiary aim was to address limitations of meta-analyses as they pertain to findings from this meta-analysis.

DESIGN

We searched multiple databases for interventional studies that evaluated the effect of increased protein intake on fullness ratings. Inclusion criteria for both analyses were as follows: healthy human participants, preload studies that utilized intact dietary protein, delivery of protein load orally, and studies reporting fullness as an outcome. For the meta-analysis, an additional criterion was that the studies also needed to report 2- to 4-hour area under the curve value for fullness.

RESULTS

Five studies met all criteria for the meta-analysis. Twenty-eight studies met all criteria for the directional analysis. The meta-analysis indicated higher protein preloads have a greater effect on fullness than lower protein preloads (overall effect estimate: 2,435.74 mm.240 min, (95% CI 1,375.18 to 3,496.31 mm.240 min; P<0.0001). The directional analysis also revealed a positive effect on fullness with higher protein preloads (P<0.01). Many related scientifically rigorous studies were excluded from the analysis because analytical criteria required a narrowly focused research question.

CONCLUSIONS

The present analyses show that higher protein preloads increase fullness ratings more than lower protein preloads under tightly defined conditions. Extrapolation of findings to common conditions outside the specified criteria of this analysis must be made cautiously, as must speculation about the influence of fullness sensations on ingestive behavior, body weight, and various health outcomes.

No Difference in Perceived Intensity of Linoleic Acid in the Oral Cavity between Obese and Nonobese Individuals

Findings from studies examining interactions between fat taste and dietary fat intake or body weight are mixed. A convenience sample of 735 visitors to the Denver Museum of Nature & Science ≥8 years old rated the taste intensity of edible taste strips impregnated with varying concentrations (%v/v) of linoleic acid (LA) (blank = 0.0, low = 0.06, medium = 0.15, high = 0.38). Percent body fat (BF%) was measured using bioelectrical impedance. Fat taste intensity was rated as significantly different across all concentrations (P < 0.001) except between the blank and low concentrations (P = 0.1). Ratings increased monotonically across concentrations. Children (<18 years; N = 180) rated all concentrations as more intense than adults (P < 0.001 for all). Women and girls rated the highest concentration as more intense than men and boys (P < 0.02 for all). BF% was not correlated with fat taste intensity ratings. Self-reported dietary intake indicated that obese individuals’ intensity ratings for medium and high concentrations of LA were inversely related to recent mono- and poly-unsaturated fat exposure (r = −0.19 to −0.27; P < 0.03 for all). No such associations were observed in the nonobese group. Findings suggest that factors other than simple adiposity status influence fat taste intensity ratings, and that participants in fat taste studies should receive standardized meals prior to testing.

Oleogustus: The Unique Taste of Fat

Considerable mechanistic data indicate there may be a sixth basic taste: fat. However, evidence demonstrating that the sensation of nonesterified fatty acids (NEFA, the proposed stimuli for "fat taste") differs qualitatively from other tastes is lacking. Using perceptual mapping, we demonstrate that medium and long-chain NEFA have a taste sensation that is distinct from other basic tastes (sweet, sour, salty, and bitter). Although some overlap was observed between these NEFA and umami taste, this overlap is likely due to unfamiliarity with umami sensations rather than true similarity. Shorter chain fatty acids stimulate a sensation similar to sour, but as chain length increases this sensation changes. Fat taste oral signaling, and the different signals caused by different alkyl chain lengths, may hold implications for food product development, clinical practice, and public health policy.

The apéritif effect: Alcohol's effects on the brain's response to food aromas in women

OBJECTIVE

Consuming alcohol prior to a meal (an apéritif) increases food consumption. This greater food consumption may result from increased activity in brain regions that mediate reward and regulate feeding behavior. Using functional magnetic resonance imaging, we evaluated the blood oxygenation level dependent (BOLD) response to the food aromas of either roast beef or Italian meat sauce following pharmacokinetically controlled intravenous infusion of alcohol.

METHODS

BOLD activation to food aromas in non-obese women (n = 35) was evaluated once during intravenous infusion of 6% v/v EtOH, clamped at a steady-state breath alcohol concentration of 50 mg%, and once during infusion of saline using matching pump rates. Ad libitum intake of roast beef with noodles or Italian meat sauce with pasta following imaging was recorded.

RESULTS

BOLD activation to food relative to non-food odors in the hypothalamic area was increased during alcohol pre-load when compared to saline. Food consumption was significantly greater, and levels of ghrelin were reduced, following alcohol.

CONCLUSIONS

An alcohol pre-load increased food consumption and potentiated differences between food and non-food BOLD responses in the region of the hypothalamus. The hypothalamus may mediate the interplay of alcohol and responses to food cues, thus playing a role in the apéritif phenomenon.

Anticipatory and reactive responses to chocolate restriction in frequent chocolate consumers

OBJECTIVE

Many individuals have difficulty adhering to a weight loss diet. One possible explanation could be that dietary restriction paradoxically contributes to overconsumption. The objective of this study was to examine ingestive behavior under a forced chocolate restriction with a focus on the anticipatory restriction period and the post-restriction period in frequent chocolate consumers.

METHODS

Fifty-six male (N = 18) and female (N = 38) high chocolate consumers with high (N = 25) or low (N = 31) cognitive disinhibition participated. Chocolate snacks were provided for a week each to establish baseline, pre-restriction, and post-restriction consumption, Chocolate snacks were replaced with nonchocolate snacks during a 3-week chocolate restriction period.

RESULTS

Highly disinhibited participants felt more guilty and consumed significantly more energy than low disinhibited participants across snack conditions. Low disinhibited participants consumed significantly less in the post-restriction period compared to baseline and the pre-restriction period, while high disinhibited participants consumed the same amount across all conditions. Aggregating the data, high and low disinhibited chocolate consumers ate snacks more frequently in the pre- and post-restriction periods compared to the baseline period.

CONCLUSIONS

This study suggests that for some individuals, restriction of a preferred food like chocolate may be contraindicated for energy restriction and weight management.

The role of protein in weight loss and maintenance

Over the past 20 y, higher-protein diets have been touted as a successful strategy to prevent or treat obesity through improvements in body weight management. These improvements are thought to be due, in part, to modulations in energy metabolism, appetite, and energy intake. Recent evidence also supports higher-protein diets for improvements in cardiometabolic risk factors. This article provides an overview of the literature that explores the mechanisms of action after acute protein consumption and the clinical health outcomes after consumption of long-term, higher-protein diets. Several meta-analyses of shorter-term, tightly controlled feeding studies showed greater weight loss, fat mass loss, and preservation of lean mass after higher-protein energy-restriction diets than after lower-protein energy-restriction diets. Reductions in triglycerides, blood pressure, and waist circumference were also reported. In addition, a review of the acute feeding trials confirms a modest satiety effect, including greater perceived fullness and elevated satiety hormones after higher-protein meals but does not support an effect on energy intake at the next eating occasion. Although shorter-term, tightly controlled feeding studies consistently identified benefits with increased protein consumption, longer-term studies produced limited and conflicting findings; nevertheless, a recent meta-analysis showed persistent benefits of a higher-protein weight-loss diet on body weight and fat mass. Dietary compliance appears to be the primary contributor to the discrepant findings because improvements in weight management were detected in those who adhered to the prescribed higher-protein regimen, whereas those who did not adhere to the diet had no marked improvements. Collectively, these data suggest that higher-protein diets that contain between 1.2 and 1.6 g protein · kg^-1 · d^-1 and potentially include meal-specific protein quantities of at least ∼25-30 g protein/meal provide improvements in appetite, body weight management, cardiometabolic risk factors, or all of these health outcomes; however, further strategies to increase dietary compliance with long-term dietary interventions are warranted.

Food reward system: current perspectives and future research needs

This article reviews current research and cross-disciplinary perspectives on the neuroscience of food reward in animals and humans, examines the scientific hypothesis of food addiction, discusses methodological and terminology challenges, and identifies knowledge gaps and future research needs. Topics addressed herein include the role of reward and hedonic aspects in the regulation of food intake, neuroanatomy and neurobiology of the reward system in animals and humans, responsivity of the brain reward system to palatable foods and drugs, translation of craving versus addiction, and cognitive control of food reward. The content is based on a workshop held in 2013 by the North American Branch of the International Life Sciences Institute.

Humans are more sensitive to the taste of linoleic and α-linolenic than oleic acid

Health concerns have led to recommendations to replace saturated fats with unsaturated fats. However, addition of unsaturated fatty acids may lead to changes in the way foods are perceived in the oral cavity. This study tested the taste sensitivity to and emulsion characteristics of oleic, linoleic, and α-linolenic acids. The hypothesis tested was that oral sensitivity to nonesterified fatty acids would increase with degree of unsaturation but that in vitro viscosities and particle sizes of these emulsions would not differ. Oral taste thresholds were obtained using the three-alternative, forced-choice, ascending method. Each participant was tested on each fat 7 times, for a total of 21 study visits, to account for learning effects. Viscosities were obtained for the blank solutions and all three emulsions. Results indicate lower oral thresholds to linoleic and α-linolenic than oleic acid. At higher shear rates, 5% oleic and linoleic acid were more viscous than other samples. More-dilute emulsions showed no significant differences in viscosity. Particle sizes of the emulsions increased very slightly with increasing unsaturation. Together, the emulsion characteristics and oral sensitivity data support a taste mechanism for nonesterified fatty acid detection.

Candy consumption patterns, effects on health, and behavioral strategies to promote moderation: summary report of a roundtable discussion

Nearly all Americans (97%) report eating candy at least once per year; yet, on a given day, only approximately one-fourth of the US population aged ≥2 y consumes candy. Among all Americans, candy contributes a relatively small proportion of calories, added sugars, and saturated fat to the total diet, and recent research suggests that current levels of candy consumption are not associated with risk of weight gain and cardiovascular disease in children and adults. Providing guidance for the consumption of candy in moderation requires an understanding of various behavioral health-related factors that influence candy consumption. A roundtable of behavioral nutrition experts, researchers, and nutrition educators met to discuss recent data on intakes of candy, health outcomes associated with usual candy intake, and the impact of behavioral strategies, including restriction, education, and environmental awareness, on modifying eating behaviors to achieve moderate intakes of candy. Restricting access to palatable foods, whether self-imposed or by parental control, may have potentially negative consequences. Techniques and insight into how to adopt "moderation" in candy consumption, from effective parental practices to environmental strategies that facilitate behavior change without a high degree of effort, were identified as important next steps toward sustainable dietary guidance related to the role of candy and other treats in a healthy lifestyle.

Effects of learning and food form on energy intake and appetitive responses

Energy-yielding beverages reportedly contribute to positive energy balance uniquely. They are highly consumed and evoke weaker satiety signaling and dietary energy compensation than solid foods of the same energy content. This study measured the contribution of learning to appetitive sensations and adjustments of energy intake for preloads varying in energy content and food form in lean and obese adults. One-hundred seven participants received four preload trials before and after a dietary intervention in this randomized cross-over trial with the stipulation that lean and obese individuals were evenly assigned to each intervention. The study entailed monitoring appetitive sensations and daily energy intake after consumption of low and high energy beverage and solid food loads on weekly visit days. Preload testing was conducted at baseline, followed by daily ingestion of one load for 14 days and then retesting responses to the four treatments. Lean individuals compensated precisely for the high energy beverage and solid loads from the onset of the study, whereas the obese did not alter eating patterns after consuming the higher energy beverage load. The learning intervention did not have an effect on the responses to the preloads, as responses in both lean and obese participants did not differ from baseline values. Responses to personality and eating behavior questionnaires revealed differences between the lean and obese groups and weakly, but significantly, predicted challenge meal and total daily energy intake. These data suggest that lean and obese individuals respond to energy in beverage form differently, and this is not altered by purposeful daily exposure to loads varying in physical form and energy content for two weeks.

No protein intake compensation for insufficient indispensable amino acid intake with a low-protein diet for 12 days

Background

Protein quality evaluation aims to determine the capacity of food sources and diets to meet protein and indispensable amino acid (IAA) requirements. This study determined whether nitrogen balance was affected and whether dietary IAA were adequately obtained from the ad libitum consumption of diets at three levels of protein from different primary sources for 12 days.

Methods

Two 12-day randomized crossover design trials were conducted in healthy subjects [n = 70/67 (M/F); age: 19-70 y; BMI: 18.2-38.7 kg/m²]. The relative dietary protein content was lower than [5% of energy (En%)], similar to (15En%), and higher than (30En%) customary diets. These diets had a limited variety of protein sources, containing wheat protein as a single protein source (5En%-protein diet) or 5En% from wheat protein with 10En% (15En%-protein diets) or 25En% (30En%-protein diets) added from whey with α-lactalbumin, soy or beef protein.

Results

There was a dose-dependent increase in nitrogen excretion with increasing dietary protein content, irrespective of the protein sources (P = 0.001). Nitrogen balance was maintained on the 5En%-protein diet, and was positive on the 15En%- and 30En%-protein diets (P < 0.001) over 12 days. Protein intake from the 5En%-protein diet did not reach the amount necessary to meet the calculated minimal IAA requirements, but IAA were sufficiently obtained from the 15En%- and 30En%-protein diets. In the 15En%- and 30En%-protein conditions, a higher protein intake from the soy-containing diets than from the whey with α-lactalbumin or beef containing diets was needed to meet the minimal IAA requirements.

Conclusion

Protein intake did not compensate for an insufficient indispensable amino acid intake with a low-protein diet for 12 days.

Trial registration

These trials were registered at clinicaltrials.gov as NCT01320189 and NCT01646749.

Different oral sensitivities to and sensations of short-, medium-, and long-chain fatty acids in humans

Fatty acids that vary in chain length and degree of unsaturation have different effects on metabolism and human health. As evidence for a "taste" of nonesterified fatty acids (NEFA) accumulates, it may be hypothesized that fatty acid structures will also influence oral sensations. The present study examined oral sensitivity to caproic (C6), lauric (C12), and oleic (C18:1) acids over repeated visits. Analyses were also conducted on textural properties of NEFA emulsions and blank solutions. Oral thresholds for caproic acid were lower compared with oleic acid. Lauric acid thresholds were intermediate but not significantly different from either, likely due to lingering irritating sensations that prevented accurate discrimination. From particle size analysis, larger droplets were observed in blank solutions when mineral oil was used, leading to instability of the emulsion, which was not observed when emulsions contained NEFA or when mineral oil was removed from the blank. Rheological data showed no differences in viscosity among samples except for a slightly higher viscosity with oleic acid concentrations above 58 mM. Thus, texture was unlikely to be the property used to distinguish between the samples. Differences in oral detection and sensation of caproic, lauric, and oleic acids may be due to different properties of the fatty acid alkyl chains.

Increased fruit and vegetable intake has no discernible effect on weight loss: a systematic review and meta-analysis

BACKGROUND

A common dietary recommendation for weight loss, especially in lay public outlets, is to eat more fruit and vegetables (F/Vs). Without a compensatory reduction in total energy intake, significant weight loss would be unlikely.

OBJECTIVE

We aimed to synthesize the best available evidence on the effectiveness of the general recommendation to eat more F/Vs for weight loss or the prevention of weight gain.

DESIGN

We searched multiple databases for human randomized controlled trials that evaluated the effect of increased F/V intake on body weight. Inclusion criteria were as follows: ≥15 subjects/ treatment arm, ≥8-wk intervention, a stated primary or secondary outcome of body weight, the stated goal of the intervention was weight or fat loss or the prevention of weight or fat gain, and food intake provided or prescribed was of a variety of F/Vs that remained minimally processed.

RESULTS

Two studies met all criteria; 5 other studies met all criteria but one. The primary analysis indicated an effect size of weight change (outcome of interest) from baseline [standardized mean difference (SMD) for studies that met all criteria] of -0.16 (95% CI: -0.78, 0.46) (P = 0.60). The SMD for 7 studies that met all or most criteria was 0.04 (95% CI: -0.10, 0.17) (P = 0.62).

CONCLUSIONS

Studies to date do not support the proposition that recommendations to increase F/V intake or the home delivery or provision of F/Vs will cause weight loss. On the basis of the current evidence, recommending increased F/V consumption to treat or prevent obesity without explicitly combining this approach with efforts to reduce intake of other energy sources is unwarranted. This systematic review and meta-analysis was registered at http://www.crd.york.ac.uk/PROSPERO/ as CRD42013004688.

Effects of daily consumption of one or varied peanut flavors on acceptance and intake

To realize the health benefits associated with peanut consumption, it is important that they remain acceptable with regular intake. Peanuts are marketed with various flavorings so that consumers will not become fatigued by frequent consumption of any single flavor. This study sought to determine whether liking of peanuts or compliance to a peanut feeding intervention would differ based on receiving an individual flavor or a variety of flavors. Participants (n=151) were directed to consume 42 g peanuts/d for 12 weeks as 14-g servings of 3 different flavors (n=50) or a single flavor (n=25-26/group). The trial was randomized, with a parallel-group design. Neither the peanut flavor consumed nor the presence of variety had an impact on liking of the peanuts or compliance with the study protocol (p>0.05). Men had significantly greater compliance and liking ratings than women (p<0.05), but liking declines did not differ based on sex. Eating attitudes and dietary restraint did not correlate with liking or compliance. Peanuts were generally well-liked in the study, with a mean liking of 69 on a 100-mm visual analogue scale and a decrease of less than 15% over 12 weeks. Overall compliance to the protocol was 96.9%, suggesting participants were able to incorporate peanuts into their diet on a daily basis. These findings suggest a recommendation to regularly consume peanuts would be well-tolerated, facilitating their contribution to a healthy diet. The study was conducted between February 2010 and May 2012 at Purdue University, West Lafayette, IN, USA. This trial was registered at clinicaltrials.gov as NCT01886326.