A Randomized Trial of Healthy Weight Gain in Athletic Individuals.

PURPOSE: To evaluate the outcomes of a 10-week diet and exercise regimen designed to promote healthy weight gain with excess energy from peanut-containing or high-carbohydrate foods. METHODS: 19 male and 13 female athletes were randomly assigned to receive 500 additional kcal/day above typical intake through provision of either peanut-based whole foods/snacks (PNT group) or a similar, high-carbohydrate, peanut-free snack (CHO group) along with supervised, whole-body RT (3 days/week for 60-120 minutes). Body composition was assessed by dual-energy x-ray absorptiometry at baseline and post-intervention. Results: Total body mass (TBM) increased 2.2 ± 1.3 kg with 1.5 ± 1.1 kg as LBM after week 10. The PNT group (N = 16; 27 ± 7 years; 10 men, 6 women) gained less TBM than the CHO group (N = 16; 23 ± 3 years; 9 men, 7 women) (1.6 ± 1.1 kg vs 2.7 ± 1.2 kg, respectively, P = 0.007) with no differences in LBM (1.2 ± 1.1 kg vs 1.9 ± 1.0 kg, P = 0.136). CONCLUSIONS: These results suggest that the addition of 500 kcal/day from whole foods/snacks in combination with a rigorous RT program promotes a similar weight gain of ~0.22 kg/week, primarily as LBM, over 10 weeks in both male and female athletes. However, snack macronutrient content may impact the effectiveness of this regimen.

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

BACKGROUND: Aging is associated with gut dysbiosis, low-grade inflammation, and increased risk of type 2 diabetes (T2D). Prediabetes, which increases T2D and cardiovascular disease risk, is present in 45-50% of mid-life adults. The gut microbiota may link ultra-processed food (UPF) with inflammation and T2D risk. METHODS: Following a 2-week standardized lead-in diet (59% UPF), adults aged 40-65 years will be randomly assigned to a 6-week diet emphasizing either UPF (81% total energy) or non-UPF (0% total energy). Measurements of insulin sensitivity, 24-h and postprandial glycemic control, gut microbiota composition/function, fecal short chain fatty acids, intestinal inflammation, inflammatory cytokines, and vascular function will be made before and following the 6-week intervention period. Prior to recruitment, menus were developed in order to match UPF and non-UPF conditions based upon relevant dietary factors. Menus were evaluated for palatability and costs, and the commercial additive content of study diets was quantified to explore potential links with outcomes. RESULTS: Overall diet palatability ratings were similar (UPF = 7.6 ± 1.0; Non-UPF = 6.8 ± 1.5; Like Moderately = 7, Like Very Much = 8). Cost analysis (food + labor) of the 2000 kcal menu (7-d average) revealed lower costs for UPF compared to non-UPF diets ($20.97/d and $40.23/d, respectively). Additive exposure assessment of the 2000 kcal UPF diet indicated that soy lecithin (16×/week), citric acid (13×/week), sorbic acid (13×/week), and sodium citrate (12×/week) were the most frequently consumed additives. CONCLUSIONS: Whether UPF consumption impairs glucose homeostasis in mid-life adults is unknown. Findings will address this research gap and contribute information on how UPF consumption may influence T2D development.

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

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

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

BACKGROUND: The greatest age-related weight gain occurs in the early/mid-20s. Overall dietary quality among adolescents and emerging adults (age 18-25) is poor, with ultra-processed foods (UPF) representing more than two-thirds of adolescents' total energy intake (i.e., 68%). UPF consumption may impact cognitive and neurobiological factors that influence dietary decision-making and energy intake (EI). To date, no research has addressed this in this population. METHODS: Participants aged 18-25 will undergo two 14-day controlled feeding periods (81% UPF, 0% UPF) using a randomly assigned crossover design, with a 4-week washout between conditions. Brain response to a UPF-rich milkshake, as well as behavioral measures of executive function, will be evaluated before and after each diet. Following each diet, measurements include ad libitum buffet meal EI, food selection, eating rate, and eating in the absence of hunger (EAH). Prior to initiating recruitment, controlled diet menus, buffet, and EAH snacks were developed and evaluated for palatability. Sensory and texture attributes of buffet and EAH snack foods were also evaluated. RESULTS: Overall diet palatability was rated "like very much" (8)/"like moderately"(7) (UPF: 7.6 ± 1.0; Non-UPF: 6.8 ± 1.5). Subjective hardness rating (range = 1-9 [1 = soft, 9 = hard] was similar between UPF and Non-UPF buffet and snack items (UPF:4.22 ± 2.19, Non-UPF: 4.70 ± 2.03), as was the objective measure of hardness (UPF: 2874.33 ± 2497.06 g, Non-UPF: 2243.32 ± 1700.51 g). CONCLUSIONS: Findings could contribute to an emerging neurobiological understanding of the effects of UPF consumption including energy overconsumption and weight gain among individuals at a critical developmental stage.

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

OBJECTIVES: Using equations to predict resting metabolic rate (RMR) has yielded different degrees of validity, particularly when sex and different physical activity levels were considered. Therefore, the purpose of the present study was to determine the validity of several different predictive equations to estimate RMR in female and male adults with varying physical activity levels. METHOD: We measured the RMR of 50 adults (26 females and 24 males) evenly distributed through activity levels varying from sedentary to ultra-endurance. Body composition was measured by dual X-ray absorptiometry and physical activity was monitored by accelerometry. Ten equations to predict RMR were applied (using Body Mass [BM]: Harris & Benedict, 1919; Mifflin et al., 1990 [MifflinBM ]; Pontzer et al., 2021 [PontzerBM ]; Schofield, 1985; FAO/WHO/UNU, 2004; and using Fat-Free Mass (FFM): Cunningham, 1991; Johnstone et al., 2006; Mifflin et al., 1990 [MifflinFFM ]; Nelson et al. 1992; Pontzer et al., 2021 [PontzerFFM ]). The accuracy of these equations was analyzed, and the effect of sex and physical activity was evaluated using different accuracy metrics. RESULTS: Equations using BM were less accurate for females, and their accuracy was influenced by physical activity and body composition. FFM equations were slightly less accurate for males but there was no obvious effect of physical activity or other sample parameters. PontzerFFM provides higher accuracy than other models independent of the magnitude of RMR, sex, activity levels, and sample characteristics. CONCLUSION: Equations using FFM were more accurate than BM equations in our sample. Future studies are needed to test the accuracy of RMR prediction equations in diverse samples.

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

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

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

Objective: To evaluate the effectiveness of two technology-enhanced interventions for diabetes prevention among adults at risk for developing diabetes in a primary care setting. Methods: The DiaBEAT-it study employed a hybrid 2-group preference (Choice) and 3-group randomized controlled (RCT) design. This paper presents weight related primary outcomes of the RCT arm. Patients from Southwest Virginia were identified through the Carilion Clinic electronic health records. Eligible participants (18 and older, BMI ≥ 25, no Type 2 Diabetes) were randomized to either Choice (n = 264) or RCT (n = 334). RCT individuals were further randomized to one of three groups: (1) a 2-h small group class to help patients develop a personal action plan to prevent diabetes (SC, n = 117); (2) a 2-h small group class plus automated telephone calls using an interactive voice response system (IVR) to help participants initiate weight loss through a healthful diet and regular physical activity (Class/IVR, n = 110); or (3) a DVD with same content as the class plus the same IVR calls over a period of 12 months (DVD/IVR, n = 107). Results: Of the 334 participants that were randomized, 232 (69%) had study measured weights at 6 months, 221 (66%) at 12 months, and 208 (62%) at 18 months. Class/IVR participants were less likely to complete weight measures than SC or DVD/IVR. Intention to treat analyses, controlling for gender, race, age and baseline BMI, showed that DVD/IVR and Class/IVR led to reductions in BMI at 6 (DVD/IVR -0.94, p < 0.001; Class/IVR -0.70, p < 0.01), 12 (DVD/IVR -0.88, p < 0.001; Class/IVR-0.82, p < 0.001) and 18 (DVD/IVR -0.78, p < 0.001; Class/IVR -0.58, p < 0.01) months. All three groups showed a significant number of participants losing at least 5% of their body weight at 12 months (DVD/IVR 26.87%; Class/IVR 21.62%; SC 16.85%). When comparing groups, DVD/IVR were significantly more likely to decrease BMI at 6 months (p < 0.05) and maintain the reduction at 18 months (p < 0.05) when compared to SC. There were no differences between the other groups. Conclusions: The DiaBEAT-it interventions show promise in responding to the need for scalable, effective methods to manage obesity and prevent diabetes in primary care settings that do not over burden primary care clinics and providers. Registration: https://clinicaltrials.gov/ct2/show/NCT02162901, identifier: NCT02162901.

Preliminary Assessment of the Healthy Beverage Index for US Children and Adolescents: A Tool to Quantify the Overall Beverage Intake Quality of 2- to 19-Year Olds.

BACKGROUND: Improving beverage patterns of children and adolescents is recommended for combatting obesity and reducing disease risk. Therefore, it is important to assess beverage intake quality in this population. For adults, the Healthy Beverage Index (HBI) was created to assess beverage intake quality, but a similar tool did not exist for children and adolescents. OBJECTIVE: The objective was to develop an HBI for US Children and Adolescents (HBI-CA), and then assess the validity and reliability of this tool. DESIGN: Modeled after the adult HBI, age-specific, evidence-based beverage recommendations were compiled. Ten components were included to assess beverage intake quality. Validity and reliability were assessed using cross-sectional data and methods similar to those used for the evaluation of the Healthy Eating Index. PARTICIPANTS: The 2015-2016 National Health and Nutrition Examination Survey provided 24-hour dietary recall data for 2,874 children and adolescents aged 2 to 19 years. MAIN OUTCOME MEASURES: HBI-CA scores were the main outcome measure. STATISTICAL ANALYSES PERFORMED: To assess validity, independent t tests were used to determine differences in HBI-CA component and total scores among groups, and principal component analysis was completed to examine multidimensionality of the HBI-CA. Pearson bivariate correlations were used to assess reliability. RESULTS: The HBI-CA produced a (mean ± standard error) total score of 69.2 ± 0.8, which is similar to the adult HBI mean total score of 63. Principal component analysis identified six factors, indicating the multidimensionality of the HBI-CA, with more than one combination of components contributing to variation in total scores. Most HBI-CA components were significantly correlated to the total score, with met fluid requirements, total beverage energy, sugar-sweetened beverage, and water components demonstrating the strongest correlations (r range = 0.335-0.735; P ≤ 0.01). CONCLUSIONS: The results provide preliminary evidence to support the validity and reliability of the HBI-CA. If future research establishes the predictive validity and sensitivity of the HBI-CA, this tool could be useful to quantify the beverage intake quality of children and adolescents.

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

PURPOSE OF REVIEW: Improving beverage patterns is important for promoting the health of children and adolescents. Food preferences can begin developing at a young age; thus, children and adolescents should be provided healthy beverages in accordance with current recommendations. The purpose of this review is to identify and summarize existing beverage recommendations for children and adolescents. This review also discusses the health impacts of beverages and how beverage consumption has changed among children and adolescents over time. RECENT FINDINGS: The mean number of calories that children and adolescents are consuming from beverages on a given day has declined in recent years. However, sugar-sweetened beverages (SSB) are the primary source of added sugars in this population. Therefore, SSB consumption remains a concern, and reducing the intake of SSB is still considered a top priority for helping to improve dietary quality. This review uniquely compiles recommendations into one convenient table for the entire age range of 0-19 years and includes recommendations that can be more adequately individualized. Beverage categories where beverage recommendations from authoritative sources are lacking have also been identified. Potential methods that can be implemented to improve beverage patterns and current public policy recommendations have been discussed to provide actionable steps that public health professionals can utilize in practice. The comprehensive table of beverage recommendations could be useful for professionals promoting the health of children and adolescents in research, clinical, and public health settings.

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

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

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

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

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

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

Evaluation of Pragmatic Methods to Rapidly Assess Habitual Beverage Intake and Hydration Status in U.S. Collegiate Athletes.

Fluid intake recommendations have been established for the athletic population in order to promote adequate hydration. The Beverage Intake Questionnaire (BEVQ-15) is a quick and reliable food frequency questionnaire that quantifies habitual beverage intake, which has been validated in children, adolescents, and adults. However, no validated beverage consumption questionnaire is available for collegiate athletes. Urine color (UC), while feasible for determining hydration status, has not been validated within a variety of collegiate athletes. The purpose of this investigation was to evaluate the comparative validity and reliability of pragmatic methods to rapidly assess BEVQ-15 and UC rating in U.S. Division I collegiate athletes. Student-athletes (n = 120; 54% females; age 19 ± 1 years) from two universities were recruited to complete three study sessions. At the first and third sessions, the participants completed the BEVQ-15 and provided a urine sample to determine UC and urinary specific gravity. All sessions included completion of a 24-hr dietary recall. Total fluid intake (fl oz) was 111 ± 107 and 108 ± 42 using the BEVQ-15 and the mean of three 24-hr dietary recalls, respectively, which was not different between methods (p > .05). There were moderate associations between the BEVQ-15 and dietary recall results for total beverage intake fl oz and kcal(r = .413 and r = 4.65; p ≤ .05, respectively). Strong associations were noted between both researcher-rated and participant-rated UC with urinary specific gravity measures (r = .675 and r = .884; p ≤ .05, respectively). Therefore, these rapid assessment methods demonstrated acceptable validity and may be used as practical methods to determine whether athletes are meeting their hydration recommendations.

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

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

Changes in Non-Nutritive Sweetener Consumption Patterns in Response to a Sugar-Sweetened Beverage Reduction Intervention.

Data are lacking on whether non-nutritive sweeteners (NNS) can be used as a strategy to support decreases in sugar-sweetened beverage (SSB) consumption. The purpose of this secondary analysis of a 6-month SSB-reduction intervention was to explore changes in NNS consumption patterns in Talking Health participants within the SIPsmartER (n = 101) intervention. Additionally, participant characteristics were compared for three SSB-NNS change groups (decrease SSB/increase NNS; decrease SSB/no increase in NNS; increase/no change in SSB/regardless of NNS). There was a significant increase in aspartame and total NNS intake for participants (mean daily mg increases of 37.2 ± 13.9 and 63.7 ± 18.5, respectively). With the exception of sex, no differences in participant characteristics were found between the three SSB-NNS change groups. Furthermore, no significant changes in weight or body mass index (BMI) were demonstrated between SSB-NNS change groups over time. Diet soda was the most commonly consumed source of NNS; however, other dietary sources of NNS also contributed to intake. At 6 months, intake of sucralose and saccharin were primarily from dietary sources other than diet sodas (94% and 100%, respectively). These findings suggest that NNS may be a feasible strategy to help reduce SSB consumption. This study supports the need to consistently quantify and identify NNS intake, beyond using diet soda intake as a proxy for NNS intake and grouping all NNS types into one variable, to more accurately address the potential health effects of NNS.

Overfeeding and Substrate Availability, But Not Age or BMI, Alter Human Satellite Cell Function.

Satellite cells (SC) aid skeletal muscle growth and regeneration. SC-mediated skeletal muscle repair can both be influenced by and exacerbate several diseases linked to a fatty diet, obesity, and aging. The purpose of this study was to evaluate the effects of different lifestyle factors on SC function, including body mass index (BMI), age, and high-fat overfeeding. For this study, SCs were isolated from the vastus lateralis of sedentary young (18-30 years) and sedentary older (60-80 years) men with varying BMIs (18-32 kg/m2), as well as young sedentary men before and after four weeks of overfeeding (OVF) (55% fat/ + 1000 kcal, n = 4). The isolated SCs were then treated in vitro with a control (5 mM glucose, 10% fetal bovine serum (FBS)) or a high substrate growth media (HSM) (10% FBS, 25 mM glucose, and 400 µM 2:1 oleate-palmitate). Cells were assessed on their ability to proliferate, differentiate, and fuel substrate oxidation after differentiation. The effect of HSM was measured as the percentage difference between SCs exposed to HSM compared to control media. In vitro SC function was not affected by donor age. OVF reduced SC proliferation rates (-19% p < 0.05) but did not influence differentiation. Cellular proliferation in response to HSM was correlated to the donor's body mass index (BMI) (r2 = 0.6121, p < 0.01). When exposed to HSM, SCs from normal weight (BMI 18-25 kg/m2) participants exhibited reduced proliferation and fusion rates with increased fatty-acid oxidation (p < 0.05), while SCs from participants with higher BMIs (BMI 25-32 kg/m2) demonstrated enhanced proliferation in HSM. HSM reduced proliferation and fusion (p < 0.05) in SCs isolated from subjects before OVF, whereas HSM exposure accelerated proliferation and fusion in SCs collected following OVF. These results indicated that diet has a greater influence on SC function than age and BMI. Though age and BMI do not influence in vitro SC function when grown in controlled conditions, both factors influenced the response of SCs to substrate challenges, indicating age and BMI may mediate responses to diet.

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

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

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

BACKGROUND: Our previous work demonstrated that a short-term high fat diet (HFD) increased fasting serum endotoxin, altered postprandial excursions of serum endotoxin, and led to metabolic and transcriptional responses in skeletal muscle in young, healthy male humans. PURPOSE: The purpose of the present study was to determine if a short-term high fat diet: 1) increases intestinal permeability and, in turn, fasting endotoxin concentrations and 2) decreases postprandial skeletal muscle fat oxidation. METHODS: Thirteen normal weight young adult males (BMI 23.1 ±â€¯0.8 kg/m2, age 22.2 ±â€¯0.4 years) were fed a control diet (55% carbohydrate, 30% fat, 9% of which was saturated, 15% protein) for two weeks, followed by 5 days of an isocaloric HFD (30% carbohydrate, 55% fat, 25% of which was saturated, 15% protein, isocaloric to the control diet). Intestinal permeability (via four sugar probe test) was assessed in the fasting state. Both before and after the HFD, a high fat meal challenge (HFM, 820 kcal, 25% carbohydrate, 63% fat, 26% of which was saturated, and 12% protein) was administered. After an overnight fast, blood samples were collected before and every hour for 4 h after the HFM to assess endotoxin, and other serum blood measures. Muscle biopsies were obtained from the vastus lateralis before and 4 h after the HFM in order to assess substrate oxidation (glucose, fatty acid and pyruvate) using radiolabeled techniques. Insulin sensitivity was assessed via intravenous glucose tolerance test. Intestinal permeability, blood samples and muscle biopsies were assessed in the same manner before and following the HFD. MAIN FINDINGS: Intestinal permeability was not affected by HFD (p > 0.05), but fasting endotoxin increased two fold following the HFD (p = 0.04). Glucose oxidation and fatty acid oxidation in skeletal muscle homogenates significantly increased after the HFM before the HFD (+97%, and +106% respectively) but declined after the HFM following 5 days of the HFD (-24% and +16% respectively). Fatty acid suppressibility of pyruvate oxidation increased significantly after the HFM (+32%) but this physiological effect was abolished following 5 days of the HFD (+7%). Insulin sensitivity did not change following the HFD. CONCLUSION: These findings demonstrate that in healthy young men, consuming an isocaloric HFD for 5 days increases fasting endotoxin, independent of changes in gut permeability. These changes in endotoxin are accompanied by a broad effect on skeletal muscle substrate metabolism including increases in postprandial fat oxidation. Importantly, the latter occurs independent of changes in body weight and whole-body insulin sensitivity.

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

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