Higher Total Protein Intake and Change in Total Protein Intake Affect Body Composition but Not Metabolic Syndrome Indexes in Middle-Aged Overweight and Obese Adults Who Perform Resistance and Aerobic Exercise for 36 Weeks

Comparison of Protein- or Amino Acid-Based Supplements in the Rehabilitation of Men with Severe Obesity: A Randomized Controlled Pilot Study

BACKGROUND

Weight loss is associated with a reduction in all body compartments, including muscle mass (MM), and this effect produces a decrease in function and muscle strength. Our objective was to assess the impact of protein or amino acid supplements on MM loss in middle-aged men (age < 65 years) with severe obesity (BMI > 35 kg/m2) during weight loss.

MATERIALS AND METHODS

We conducted a single-site randomized controlled trial (Clinicaltrials.gov NCT05143398) with 40 in-patient male subjects with severe obesity. Participants underwent an intervention program consisting of a low-calorie balanced diet and structured physical activity. They were randomly assigned to 4-week treatment groups: (1) control (CTR, N = 10), (2) protein (P, N = 10), (3) branched-chain amino acid (BCAA, N = 10), and (4) essential amino acid mixture with tricarboxylic acid cycle intermediates (PD-E07, N = 10) supplementation.

RESULTS

Following 4 weeks of intervention, all groups showed similar reductions in body weight compared to baseline. When examining the delta values, a notable increase in muscle mass (MM) was observed in the PD-E07 intervention group [MM (kg): 2.84 ± 3.57; MM (%): 3.63 ± 3.14], in contrast to the CTR group [MM (kg): -2.46 ± 3.04; MM (%): -0.47 ± 2.28], with a statistical significance of p = 0.045 and p = 0.023, respectively. However, the MM values for the P group [MM (kg): -2.75 ± 5.98, p = 0.734; MM (%): -0.44 ± 4.02, p = 0.990] and the BCAA group [MM (kg): -1 ± 3.3, p = 0.734; MM (%): 0.34 ± 2.85, p = 0.956] did not exhibit a statistically significant difference when compared to the CTR group.

CONCLUSIONS

Amino acid-based supplements may effectively mitigate the loss of MM typically observed during weight reduction. Further validation through large-scale studies is necessary.

High-intensity interval training prevents muscle mass loss in overweight Chilean young adults during a hypocaloric-Mediterranean diet: a randomized trial

The hypocaloric Mediterranean diet (MD) mainly reduces fat mass but inevitably causes a loss of skeletal muscle mass. High-intensity interval training (HIIT) seems to have advantages in preserving muscle mass during a hypocaloric regime. Our study compares body composition and metabolic changes in overweight and obese Chilean women and men after 3 months of weight loss treatment with a Mediterranean-type hypocaloric diet, HIIT, or a combination of both. The study included 83 overweight or obese women and men between the ages of 25 and 50. The subjects were randomly assigned to one of the three intervention groups: (1) MD, (2) EX, and (3) MD + EX. Baseline and post-intervention measurements included: (a) body composition by dual-beam densitometry, muscle, and fat measurements by thigh ultrasound and computed tomography; (b) handgrip and quadriceps muscle strength; (c) exercise performance by peak oxygen consumption, peak load, work efficiency, and exercise energy expenditure; and (d) metabolic parameters. Out of 83 participants, the retention rate was 49% due to low compliance with the interventions. As expected, the MD group resulted in significantly greater weight loss (MD -7%, EX -0.6% and MD + EX -5.3%) and appendicular fat mass loss (MD -11.1%, EX -2.9, MD + EX -10.2%) but was associated with significant lean tissue loss (2.8%), which was prevented by HIIT (EX -0.1 and MD + EX -0.6%). Metabolic and glycoxidative parameters remained unchanged, irrespective of changes in body composition. Hypocaloric diets remain the most effective means to lose weight and body fat. However, it induces a loss of lean body mass when not accompanied by exercise training. This study shows that HIIT prevents the loss of muscle mass caused by a hypocaloric Mediterranean diet.

Effect of Protein Intake on Visceral Abdominal Fat and Metabolic Biomarkers in Older Men With Functional Limitations: Results From a Randomized Clinical Trial

BACKGROUND

It remains controversial whether high protein diets improve cardiometabolic profile. We investigated whether increasing protein intake to 1.3 g/kg/day in functionally limited older adults with usual protein intake ≤RDA (0.8 g/kg/day) improves visceral fat accumulation and serum cardiovascular risk markers more than the recommended daily allowance (RDA).

METHODS

The Optimizing Protein Intake in Older Men Trial was a placebo-controlled, randomized trial in which 92 functionally limited men, ≥65 years, with usual protein intake ≤RDA were randomized for 6 months to: 0.8 g/kg/day protein plus placebo; 1.3 g/kg/day protein plus placebo; 0.8 g/kg/day protein plus testosterone enanthate 100 mg weekly; or 1.3 g/kg/day protein plus testosterone enanthate 100 mg weekly. In this substudy, metabolic and inflammatory serum markers were measured in 77 men, and visceral adipose tissue (VAT) was assessed using dual-energy x-ray absorptiometry in 56 men.

RESULTS

Treatment groups were similar in their baseline characteristics. Randomization to 1.3 g/kg/day protein group was associated with greater reduction in VAT compared to 0.8 g/kg/day group (between-group difference: -17.3 cm2, 95% confidence interval [CI]: -29.7 to -4.8 cm2, p = .008), regardless of whether they received testosterone or placebo. Changes in fasting glucose, fasting insulin, HOMA-IR, leptin, adiponectin, IL-6, and hs-CRP did not differ between the 0.8 versus 1.3 g/kg/day protein groups regardless of testosterone use.

CONCLUSIONS

Protein intake >RDA decreased VAT in functionally limited older men but did not improve cardiovascular disease risk markers.

CLINICAL TRIALS REGISTRATION NUMBER

NCT01275365.

Protein supplementation during an energy-restricted diet induces visceral fat loss and gut microbiota amino acid metabolism activation: a randomized trial

Interactions between diet and gut microbiota are critical regulators of energy metabolism. The effects of fibre intake have been deeply studied but little is known about the impact of proteins. Here, we investigated the effects of high protein supplementation (Investigational Product, IP) in a double blind, randomised placebo-controled intervention study (NCT01755104) where 107 participants received the IP or an isocaloric normoproteic comparator (CP) alongside a mild caloric restriction. Gut microbiota profiles were explored in a patient subset (n = 53) using shotgun metagenomic sequencing. Visceral fat decreased in both groups (IP group: - 20.8 ± 23.2 cm2; CP group: - 14.5 ± 24.3 cm2) with a greater reduction (p < 0.05) with the IP supplementation in the Per Protocol population. Microbial diversity increased in individuals with a baseline low gene count (p < 0.05). The decrease in weight, fat mass and visceral fat mass significantly correlated with the increase in microbial diversity (p < 0.05). Protein supplementation had little effects on bacteria composition but major differences were seen at functional level. Protein supplementation stimulated bacterial amino acid metabolism (90% amino-acid synthesis functions enriched with IP versus 13% in CP group (p < 0.01)). Protein supplementation alongside a mild energy restriction induces visceral fat mass loss and an activation of gut microbiota amino-acid metabolism.Clinical trial registration: NCT01755104 (24/12/2012). https://clinicaltrials.gov/ct2/show/record/NCT01755104?term=NCT01755104&draw=2&rank=1 .

Weight Loss Strategies and the Risk of Skeletal Muscle Mass Loss

With energy intake restriction and exercise remaining the key diet and lifestyle approaches to weight loss, this is not without potential negative implications for body composition, metabolic health, and quality and quantity of life. Ideally, weight loss should be derived almost exclusively from the fat mass compartment as this is the main driver of metabolic disease, however, several studies have shown that there is an accompanying loss of tissue from the fat-free compartment, especially skeletal muscle. Population groups including post-menopausal women, the elderly, those with metabolic disease and athletes may be particularly at risk of skeletal muscle loss when following a weight management programme. Research studies that have addressed this issue across a range of population groups are reviewed with a focus upon the contribution of resistance and endurance forms of exercise and a higher intake dietary protein above the current guideline of 0.8 g/kg body weight/day. While findings can be contradictory, overall, the consensus appears that fat-free and skeletal muscle masses can be preserved, albeit to varying degrees by including both forms of exercise (but especially resistance forms) in the weight management intervention. Equally, higher intakes of protein can protect loss of these body compartments, acting either separately or synergistically with exercise. Elderly individuals in particular may benefit most from this approach. Thus, the evidence supports the recommendations for intakes of protein above the current guidelines of 0.8 g/kg body weight/d for the healthy elderly population to also be incorporated into the dietary prescription for weight management in this age group.

Bioactive Compounds of Porcine Hearts and Aortas May Improve Cardiovascular Disorders in Humans

Functional foods promote health benefits in human metabolism, with bioactive compounds acting as therapeutic agents. The aim was to investigate the biological effects of a pâté made of pork hearts and aortas, minced, sterilised and packed in tins. Adults (61–66 years old) with a body mass index of 26.4–60.7 kg/m² (n = 36) were randomly divided into two groups: one group consumed a low-calorie diet (LCD), while the other consumed an LCD with the developed meat product (MP) for 28–30 days. Serum biochemical parameters, anthropometry and blood pressure were measured. Consumption of an LCD + MP by experimental group participants helped to maintain reduced cholesterol levels. The difference in total cholesterol was significantly different (p = 0.018) from that of the control group, mainly due to the difference in low-density lipoprotein cholesterol (p = 0.005). Six peptides with potential cholesterol-binding properties and four peptides with potential antioxidant activity were identified in the MP, while elevation of the content of two peptides with potential angiotensin-converting enzyme-inhibitory activity was detected in patients’ plasma. Intervention with the MP can be considered as a supportive therapy to the main treatment for medical cardiovascular diseases due to a positive effect on serum cholesterol.

Association of Carbohydrate and Fat Intake with Prevalence of Metabolic Syndrome Can Be Modified by Physical Activity and Physical Environment in Ecuadorian Adults: The ENSANUT-ECU Study

The associations of lifestyle and environment with metabolic syndrome (MetS) and cardiovascular disease have recently resulted in increased attention in research. This study aimed to examine interactive associations among carbohydrate and fat intake, physical environment (i.e., elevation and humidity), lifestyle, and MetS among Ecuadorian adults. We used data from the Ecuador National Health and Nutrition Survey 2012 (ENSANUT-ECU), with a total of 6023 participants aged 20 to 60 years included in this study. Logistic regression was used to determine the association of status of carbohydrate and fat intake, low-carbohydrate high-fat diet (LCHF) and medium-carbohydrate and fat (MCF) diet with MetS, where the high-carbohydrate low-fat (HCLF) diet was used as a reference. Women with LCHF and MCF diets showed lower prevalence of increased blood pressure (OR = 0.34, 95% CI: 0.19–0.59; OR = 0.50, 95% CI: 0.32–0.79, respectively). Women with MCF diet also showed lower prevalence of elevated fasting glucose (OR = 0.58, 95% CI: 0.37–0.91). Moreover, there were negative associations between MetS and reduced HDL cholesterol in women with MCF diet residing in low relative humidity (OR = 0.66, 95% CI: 0.45–0.98) and in women with LCHF diet residing at a high elevation (OR = 0.37, 95% CI: 0.16–0.86). Additionally, higher prevalence of increased waist circumference was observed in men with both MFC and LCHF diets who were physically inactive (OR = 1.89, 95% CI: 1.12–3.20; OR = 2.34, 95% CI: 1.19–4.60, respectively) and residing in high relative humidity (OR = 1.90, 95% CI: 1.08–2.89; OR = 2.63, 95% CI: 1.32–5.28, respectively). Our findings suggest that LCHF intake is associated with lower blood pressure, while MCF intake is associated with lower blood pressure and fasting glucose in Ecuadorian women. Furthermore, the associations of carbohydrate and fat intake with prevalence of MetS can be modified by physical activity, relative humidity, and elevation. The obtained outcomes may provide useful information for health programs focusing on dietary intake and lifestyle according to physical environment of the population to promote health and prevent metabolic diseases.

Whey peptides exacerbate body weight gain and perturb systemic glucose and tissue lipid metabolism in male high-fat fed mice

Consumption of milk-derived whey proteins has been demonstrated to have insulin-sensitizing effects in mice and humans, in part through the generation of bioactive whey peptides. While whey peptides can prevent insulin resistance in vitro, it is unclear whether consumption of whey peptides can prevent obesity-induced metabolic dysfunction in vivo. We sought to determine whether whey peptides consumption can protect from high fat (HF) diet-induced obesity and dysregulation of glucose homeostasis. Male C57BL/6J mice were fed either a low or HF diet for 13 weeks. HF diet fed mice were provided drinking water with no addition (control), undigested whey protein isolate (WPI, 1 mg ml^-1) or whey protein hydrolysate (WPH, 1 mg ml^-1) throughout the diet regimen. Mice consuming WPH gained more body weight and were more glucose intolerant compared to those consuming WPI or water only. Despite increased body weight gain, perigonadal adipose tissue weight and lipid accumulation were unchanged. However, excess lipids accumulated ectopically in the liver and skeletal muscle in mice consuming WPH, which was associated with elevated inflammatory markers systemically and in adipose tissue, liver, and skeletal muscle. In skeletal muscle, mitochondrial fat oxidation and electron transport chain proteins were decreased with WPH consumption, indicative of mitochondrial dysfunction. Taken together, our results demonstrate that WPH, but not WPI, exacerbates HF-induced body weight gain and impairs glucose homeostasis, which is accompanied by increased inflammation, ectopic fat accumulation and mitochondrial dysfunction. Thus, our results argue against the use of dietary whey peptide supplementation as a preventative option against HF diet-induced metabolic dysfunction.

Protein Intake and Human Health: Implications of Units of Protein Intake

Understanding the health effects of protein intake is bedeviled by a number of factors, including protein quality and source. In addition, different units, including grams, grams per kilogram body weight (g/kg BW), and percent energy, may contribute to confusion about protein's effects on health, especially BW-based units in increasingly obese populations. We aimed to review the literature and to conduct a modeling demonstration of various units of protein intake in relation to markers of cardiometabolic health. Data from the Framingham Heart Study Offspring (n = 1847; 60.3 y; 62.5% women) and Third Generation (n = 2548; 46.2 y; 55.3% women) cohorts and the NHANES 2003-04 (n = 1625; 46.2 y; 49.7% women) and 2005-06 (n = 1347; 43.7 y; 49.5% women) cycles were used to model cross-sectional associations between 7 protein units (grams, percent energy, g/kg ideal BW, g/kg actual BW, BW-adjusted g/kg actual BW, g/kg lean BW, and g/kg fat-free BW) and 9 cardiometabolic outcomes (fasting glucose, systolic and diastolic blood pressure, total and HDL cholesterol, triglycerides, BMI, waist circumference, and estimated glomerular filtration rate). The literature review indicated the use of myriad units of protein intake, with differential results on cardiometabolic outcomes. The modeling demonstration showed units expressed in BW were confounded by BW, irrespective of outcome. Units expressed in grams, percent energy, and ideal BW showed similar results, with or without adjustment for body size. After adjusting for BW, results of units expressed in BW aligned with results of grams, percent energy, and ideal BW. In conclusion, protein intake in cardiometabolic health appears to depend on protein's unit of expression. Authors should be specific about the use of WHO (g/kg ideal BW) compared with US (g/kg actual BW) units, and ideally use gram or percent energy in observational studies. In populations where overweight/obesity are prevalent, intake based on actual BW should be reevaluated.

Effect of high-intensity resistance exercise on cardiometabolic health in older men with osteosarcopenia: the randomised controlled Franconian Osteopenia and Sarcopenia Trial (FrOST)

OBJECTIVES

Sarcopenia is related to the metabolic syndrome (MetS), a cluster of cardiometabolic risk-factors (CRF). Most exercise trials apply aerobic rather than resistance exercise to address CRF, while the strategy for maintaining muscle and bone is the opposite. However, there is considerable evidence that resistance exercise positively affects CRF. In the present study, we determined the effect of high-intensity resistance exercise training (HIT-RT) on CRF represented by the MetS in older men.

METHODS

Forty-three osteosarcopenic and predominately obese older men (>72 years) living independently in Erlangen-Nürnberg, Germany were randomly assigned to two study arms. The HIT-RT group (n=21) conducted a periodised high intensity/effort protocol dedicated to muscle and bone mass and function two times per week, while the control group (CG: n=22) maintained their habitual physical activities. Both groups were supplemented with protein, cholecalciferol and calcium. Study outcomes presented here were the MetS-Z (MetSZ) score and its underlying risk-factors.

RESULTS

After 18 months of intervention, we observed significant effects for the MetSZ score (p<0.001), with significant improvements in the HIT-RT and significant worsening in the CG. In detail, all parameters constituting the MetS contributed to this result, however, only waist-circumference, HDL-cholesterol and mean arterial blood pressure revealed significant effects. No adverse events were reported and high adherence was determined for the HIT-RT-protocol.

CONCLUSION

Continuously supervised HIT-RT is an effective, attractive, feasible and safe method to address cardiometabolic risk factors in community-dwelling men aged 72 years and older. Further, considering the proven effects on musculoskeletal risk factors, the present results indicate a more prominent role for HIT-RT within non-pharmacological prevention strategies of older adults.

TRIAL REGISTRATION NUMBER

NCT03453463.

Diurnal Regulation of Peripheral Glucose Metabolism: Potential Effects of Exercise Timing

Diurnal oscillations in energy metabolism are linked to the activity of biological clocks and contribute to whole-body glucose homeostasis. Postprandially, skeletal muscle takes up approximately 80% of circulatory glucose and hence is a key organ in maintenance of glucose homeostasis. Dysregulation of molecular clock components in skeletal muscle disrupts whole-body glucose homeostasis. Next to light-dark cycles, nonphotic cues such as nutrient intake and physical activity are also potent cues to (re)set (dys)regulated clocks. Physical exercise is one of the most potent ways to improve myocellular insulin sensitivity. Given the role of the biological clock in glucose homeostasis and the power of exercise to improve insulin sensitivity, one can hypothesize that there might be an optimal time for exercise to maximally improve insulin sensitivity and glucose homeostasis. In this review, we aim to summarize the available information related to the interaction of diurnal rhythm, glucose homeostasis, and physical exercise as a nonphotic cue to correct dysregulation of human glucose metabolism.

Novel Insights into the Pathogenesis and Management of the Metabolic Syndrome

The metabolic syndrome, by definition, is not a disease but is a clustering of individual metabolic risk factors including abdominal obesity, hyperglycemia, hypertriglyceridemia, hypertension, and low high-density lipoprotein cholesterol levels. These risk factors could dramatically increase the prevalence of type 2 diabetes and cardiovascular disease. The reported prevalence of the metabolic syndrome varies, greatly depending on the definition used, gender, age, socioeconomic status, and the ethnic background of study cohorts. Clinical and epidemiological studies have clearly demonstrated that the metabolic syndrome starts with central obesity. Because the prevalence of obesity has doubly increased worldwide over the past 30 years, the prevalence of the metabolic syndrome has markedly boosted in parallel. Therefore, obesity has been recognized as the leading cause for the metabolic syndrome since it is strongly associated with all metabolic risk factors. High prevalence of the metabolic syndrome is not unique to the USA and Europe and it is also increasing in most Asian countries. Insulin resistance has elucidated most, if not all, of the pathophysiology of the metabolic syndrome because it contributes to hyperglycemia. Furthermore, a major contributor to the development of insulin resistance is an overabundance of circulating fatty acids. Plasma fatty acids are derived mainly from the triglycerides stored in adipose tissues, which are released through the action of the cyclic AMP-dependent enzyme, hormone sensitive lipase. This review summarizes the latest concepts in the definition, pathogenesis, pathophysiology, and diagnosis of the metabolic syndrome, as well as its preventive measures and therapeutic strategies in children and adolescents.

Effect of essential amino acid supplementation and aerobic exercise on insulin sensitivity in healthy older adults: A randomized clinical trial

BACKGROUND & AIMS

The combination of prolonged essential amino acid (EAA) supplementation and aerobic exercise training (Ex) improves muscle protein metabolism, strength and function in healthy older adults. However, excess EAA intake may worsen insulin sensitivity. Here we report the effects of EAA supplementation (EAA, n = 11), placebo (PLA, n = 10), aerobic exercise with placebo (Ex + PLA, n = 11) or Ex with EAA supplementation (Ex + EAA, n = 10) for 22 weeks on insulin sensitivity in non-diabetic older adults.

METHODS

A 2 × 2 design with block randomization and double blinding for supplement or placebo was used. Subjects ingested EAA (15 g) or placebo daily. Exercising subjects participated in supervised progressive vigorous treadmill walking 3 times weekly. Measures of insulin sensitivity by oral glucose tolerance testing were collected at baseline and 22 weeks. Dietary intakes of protein and specific amino acids were determined in a subset of subjects.

RESULTS

Overall, exercise improved insulin sensitivity, while EAA supplementation had no effect. In the dietary subset, post-intervention insulin sensitivity did not correlate significantly with the total intake of EAA, anti-angiogenic amino acids (cysteine, methionine), or branched-chain amino acids (isoleucine, leucine, valine).

CONCLUSIONS

Overall, we conclude that in healthy older adults with moderate protein intake, EAA supplementation is metabolically safe as it does not decrease insulin sensitivity regardless of its combination with aerobic exercise. Thus, daily protein intake should be controlled for when modeling insulin sensitivity. Future studies should explore the role of increased blood flow as a potential explanatory factor for the observed interaction between aerobic exercise and supplementation.

CLINICAL TRIAL REGISTRATION NUMBER

NCT00872911.

Effects of Protein Intake Beyond Habitual Intakes Associated With Resistance Training on Metabolic Syndrome-Related Parameters, Isokinetic Strength, and Body Composition in Older Women

The objective of this study was to investigate the effects of protein intake beyond habitual intakes associated with resistance training on metabolic syndrome (MetS)-related parameters, isokinetic strength, and body composition in health older women. A total of 30 older women (68.8 ± 4.3 years) participated in this investigation and were assigned to receive 35 g of whey protein or placebo combined with resistance training, over 12-weeks, three times per week. Blood samples, blood pressure, dietary intake, strength, and body composition were assessed before and after the intervention period. Two-way analysis of variance for repeated measures was applied for comparisons. Both groups improved the skeletal muscle mass, muscular strength, waist circumference, triglycerides, high-density lipoprotein, glucose, resistance, reactance, and MetS Z-score risk. However, the improvements in skeletal muscle mass, waist circumference, and MetS Z-score risk were significantly greater in protein group when compared with control group. Moreover, protein group significantly decreased %body fat when compared with control group. Higher protein intake combined with resistance training promoted greater improvements in skeletal muscle mass, %body fat, waist circumference, and MetS Z-score risk in older women.

Reductions in whole-body fat mass but not increases in lean mass predict changes in cardiometabolic health indices with exercise training among weight-stable adults

We assessed whether body composition changes with 9 months of exercise training predicted changes in cardiometabolic health indices in weight-stable adults. We hypothesized that within ±5% weight change, changes in whole-body fat and lean masses would predict changes in cardiometabolic health indices with exercise training. Using a randomized parallel design, 152 adults (age: 49 ± 8 year; body mass index: 30.0 ± 2.7 kg/m²; mean ± SD) performed resistance exercises 2 d/wk and aerobic exercises 1 d/wk for 9 months. Participants consumed isoenergetic supplements with 0, 10, 20, or 30 g whey protein twice daily and remained weight stable within ±5% of baseline weight. Body weight and composition were measured using dual-energy x-ray absorptiometry pre- and postintervention. Multiple linear regression model was applied for data analyses. Independent of whey protein supplementation, reductions in fat mass predicted increases in high-density lipoprotein cholesterol (unstandardized beta-coefficient [β], -0.03; 95% confidence interval [CI], -0.06 to -0.01; P = .007) and insulin sensitivity index (β, -0.52; 95% CI, -0.95 to -0.09; P = .018) and decreases in waist circumference (β, 0.67; 95% CI, 0.17-1.18; P = .009). In contrast, increases in lean mass did not predict changes in any of the measured cardiometabolic health indices. Health improvements with training that emphasize resistance exercises are typically attributed to increases in lean mass; however, these results underscore reducing body fat to predict cardiometabolic health improvements.

Dietary protein and changes in markers of cardiometabolic health across 20 years of follow-up in middle-aged Americans

OBJECTIVE

Dietary protein plays a role in counteracting age-related muscle loss. However, limited long-term data exist on protein intake and markers of cardiometabolic health, which tend to deteriorate with age.

DESIGN

Prospective cohort study. FFQ-derived protein intake (g/d) and cardiometabolic markers were assessed up to five times across 20 years. Markers included systolic (SBP) and diastolic (DBP) blood pressures, circulating lipids (total, HDL and LDL cholesterol; TAG), estimated glomerular filtration rate (eGFR), fasting glucose (FG), weight and waist circumference (WC). Mixed models accounting for repeated measures were used to estimate adjusted mean annualized changes in outcomes per quartile category of protein.

SETTING

Framingham Heart Study Offspring cohort, USA.

SUBJECTS

Participants (n 3066) with 12 333 unique observations, baseline (mean (sd)) age=54·0 (9·7) years, BMI=27·4 (4·9) kg/m2, 53·5 % female.

RESULTS

In fully adjusted models, there were favourable associations (mean (se)) of total protein with annualized changes in SBP (lowest v. highest intake: 0·34 (0·06) v. 0·04 (0·06) mmHg, P trend=0·001) and eGFR (-1·03 (0·06) v. -0·87 (0·05) ml/min per 1·73 m2, P trend=0·046), unfavourable associations with changes in FG (0·013 (0·004) v. 0·028 (0·004) mmol/l, P trend=0·004) and no associations with weight, WC, DBP or lipids. Animal protein was favourably associated with SBP and unfavourably with FG and WC; plant protein was favourably associated with FG and WC.

CONCLUSIONS

The present study provides evidence that protein intake may influence changes in cardiometabolic health independent of change in weight in healthy adults and that protein's role in cardiometabolic health may depend on the protein source.

Effect of Protein Intake on Lean Body Mass in Functionally Limited Older Men: A Randomized Clinical Trial

Importance

The Institute of Medicine set the recommended dietary allowance (RDA) for protein at 0.8 g/kg/d for the entire adult population. It remains controversial whether protein intake greater than the RDA is needed to maintain protein anabolism in older adults.

Objective

To investigate whether increasing protein intake to 1.3 g/kg/d in older adults with physical function limitations and usual protein intake within the RDA improves lean body mass (LBM), muscle performance, physical function, fatigue, and well-being and augments LBM response to a muscle anabolic drug.

Design, Setting, and Participants

This randomized clinical trial with a 2 × 2 factorial design was conducted in a research center. A modified intent-to-treat analytic strategy was used. Participants were 92 functionally limited men 65 years or older with usual protein intake less thanor equal to 0.83 g/kg/d within the RDA. The first participant was randomized on September 21, 2011, and the last participant completed the study on January 19, 2017.

Interventions

Participants were randomized for 6 months to controlled diets with 0.8 g/kg/d of protein plus placebo, 1.3 g/kg/d of protein plus placebo, 0.8 g/kg/d of protein plus testosterone enanthate (100 mg weekly), or 1.3 g/kg/d of protein plus testosterone. Prespecified energy and protein contents were provided through custom-prepared meals and supplements.

Main Outcomes and Measures

The primary outcome was change in LBM. Secondary outcomes were muscle strength, power, physical function, health-related quality of life, fatigue, affect balance, and well-being.

Results

Among 92 men (mean [SD] age, 73.0 [5.8] years), the 4 study groups did not differ in baseline characteristics. Changes from baseline in LBM (0.31 kg; 95% CI, -0.46 to 1.08 kg; P = .43) and appendicular (0.04 kg; 95% CI, -0.48 to 0.55 kg; P = .89) and trunk (0.24 kg; 95% CI, -0.17 to 0.66 kg; P = .24) lean mass, as well as muscle strength and power, walking speed and stair-climbing power, health-related quality of life, fatigue, and well-being, did not differ between men assigned to 0.8 vs 1.3 g/kg/d of protein regardless of whether they received testosterone or placebo. Fat mass decreased in participants given higher protein but did not change in those given the RDA: between-group differences were significant (difference, -1.12 kg; 95% CI, -2.04 to -0.21; P = .02).

Conclusions and Relevance

Protein intake exceeding the RDA did not increase LBM, muscle performance, physical function, or well-being measures or augment anabolic response to testosterone in older men with physical function limitations whose usual protein intakes were within the RDA. The RDA for protein is sufficient to maintain LBM, and protein intake exceeding the RDA does not promote LBM accretion or augment anabolic response to testosterone.

Trial Registration

clinicaltrials.gov Identifier: NCT01275365.

Preserving Healthy Muscle during Weight Loss

Weight loss is the cornerstone of therapy for people with obesity because it can ameliorate or completely resolve the metabolic risk factors for diabetes, coronary artery disease, and obesity-associated cancers. The potential health benefits of diet-induced weight loss are thought to be compromised by the weight-loss-associated loss of lean body mass, which could increase the risk of sarcopenia (low muscle mass and impaired muscle function). The objective of this review is to provide an overview of what is known about weight-loss-induced muscle loss and its implications for overall physical function (e.g., ability to lift items, walk, and climb stairs). The currently available data in the literature show the following: 1) compared with persons with normal weight, those with obesity have more muscle mass but poor muscle quality; 2) diet-induced weight loss reduces muscle mass without adversely affecting muscle strength; 3) weight loss improves global physical function, most likely because of reduced fat mass; 4) high protein intake helps preserve lean body and muscle mass during weight loss but does not improve muscle strength and could have adverse effects on metabolic function; 5) both endurance- and resistance-type exercise help preserve muscle mass during weight loss, and resistance-type exercise also improves muscle strength. We therefore conclude that weight-loss therapy, including a hypocaloric diet with adequate (but not excessive) protein intake and increased physical activity (particularly resistance-type exercise), should be promoted to maintain muscle mass and improve muscle strength and physical function in persons with obesity.

Protein-Pacing and Multi-Component Exercise Training Improves Physical Performance Outcomes in Exercise-Trained Women: The PRISE 3 Study

The beneficial cardiometabolic and body composition effects of combined protein-pacing (P; 5-6 meals/day at 2.0 g/kg BW/day) and multi-mode exercise (resistance, interval, stretching, endurance; RISE) training (PRISE) in obese adults has previously been established. The current study examines PRISE on physical performance (endurance, strength and power) outcomes in healthy, physically active women. Thirty exercise-trained women (>4 days exercise/week) were randomized to either PRISE (n = 15) or a control (CON, 5-6 meals/day at 1.0 g/kg BW/day; n = 15) for 12 weeks. Muscular strength (1-RM bench press, 1-RM BP) endurance (sit-ups, SUs; push-ups, PUs), power (bench throws, BTs), blood pressure (BP), augmentation index, (AIx), and abdominal fat mass were assessed at Weeks 0 (pre) and 13 (post). At baseline, no differences existed between groups. Following the 12-week intervention, PRISE had greater gains (p < 0.05) in SUs, PUs (6 ± 7 vs. 10 ± 7, 40%; 8 ± 13 vs. 14 ± 12, 43% ∆reps, respectively), BTs (11 ± 35 vs. 44 ± 34, 75% ∆watts), AIx (1 ± 9 vs. -5 ± 11, 120%), and DBP (-5 ± 9 vs. -11 ± 11, 55% ∆mmHg). These findings suggest that combined protein-pacing (P; 5-6 meals/day at 2.0 g/kg BW/day) diet and multi-component exercise (RISE) training (PRISE) enhances muscular endurance, strength, power, and cardiovascular health in exercise-trained, active women.