Dietary protein in weight management: a review proposing protein spread and change theories

Food deprivation among adults in India: an analysis of specific food categories, 2016-2021

Background

Adult undernourishment remains pervasive throughout India, and often results from food deprivation, which refers to the inadequate consumption of foods with caloric and nutrient significance. Therefore, understanding the extent to which food groups are missing from an individual's diet is essential to understanding the extent to which they are undernourished.

Methods

We used data from two National Family Health Surveys conducted in 2016 and 2021 for this cross-sectional analysis. The study population consisted of women and pregnant women between the ages of 15-49, and men between the ages of 15-54. We examined shifts in the percentage of people not consuming dairy, pulses/beans/legumes, dark leafy green vegetables, fruits, eggs, and fish and meat among women, pregnant women, and men between the two time points. We also examined these patterns by household wealth and education, two important markers of socioeconomic status.

Findings

Overall, we found that fewer women, pregnant women, and men were not eating each of the six food groups in 2021 than in 2016. Additionally, the gap in food group consumption between women, pregnant women, and men in the lowest and highest socioeconomic groups shrank between 2016 and 2021. Yet, food group deprivation remained most prevalent among those in the lowest socioeconomic groups. The two exceptions for this were for eggs and meat/fish. Nevertheless, the majority of India's poorest and least educated adults are not consuming high-quality protein sources, including dairy, the consumption of which is far more common among wealthier and more educated Indian adults.

Interpretation

Our results show that fewer adults were not consuming important food groups in 2021 than in 2016. However, many of India's poorest and least educated adults are still not consuming high-quality sources of protein or fruits, two food groups that are essential for good health. While adults might be getting protein and nutrients from pulses, legumes, beans, and other vegetables, efforts are needed to improve affordability of, and access to, high-quality sources of protein and fruits.

Funding

This work was supported by the Bill & Melinda Gates Foundation, INV- 002992.

Consuming a Protein and Fiber-Based Supplement Preload Promotes Weight Loss and Alters Metabolic Markers in Overweight Adults in a 12-Week, Randomized, Double-Blind, Placebo-Controlled Trial

BACKGROUND

Higher protein and fiber diets promote weight management and metabolic health.

OBJECTIVES

This study aimed to determine if greater weight loss and positive changes in metabolic outcomes could be achieved with twice-daily consumption of a high-protein and fiber-based multi-ingredient nutritional shake (HPF) compared with an isocaloric low-protein, lower fiber-based placebo (LPF).

METHODS

Study procedures were conducted by an independent research organization under clinicaltrials.gov registration NCT03057873. Healthy overweight and obese adults [n = 206; BMI (kg/m2): 27-35; 70% female] were randomly assigned to HPF or LPF. All participants were prescribed an energy-restricted diet (500 kcal/d less than energy needs) and consumed a HPF (17 g protein, 6 g fiber) or LPF (1 g protein, 3 g fiber) shake 30 min before breakfast and lunch for 12 wk. Primary outcomes included body weight and total body fat percentage. Blood samples were collected at days (D) 0, 28, 56, and 84 for secondary analyses related to metabolic markers of health.

RESULTS

Although weight loss occurred in both groups, HPF had greater weight loss at D84 compared with LPF (-3.3 kg vs. -1.8 kg, P < 0.05). Percentage body fat decreased in both groups (HPF: -1.33%, LPF: -1.09%; P < 0.001) with no differences between groups. Serum total cholesterol, LDL cholesterol, and oxidized LDL decreased between -5.1% to -8.3%, whereas adiponectin increased over time in both groups; these changes occurred to a greater extent in HPF compared with LPF (all P < 0.05).

CONCLUSIONS

A multi-ingredient HPF nutritional supplement shake consumed as a preload before breakfast and lunch positively influenced weight management and metabolic outcomes in overweight adults compared with an LPF placebo. These findings suggest that specific nutrient factors (i.e., potentially including protein, fiber, and bioactive content) other than calorie reduction alone influence the success of a weight-loss regimen. This trial was registered at www.clinicaltrials.gov as NCT03057873.

Does a Higher Protein Diet Promote Satiety and Weight Loss Independent of Carbohydrate Content? An 8-Week Low-Energy Diet (LED) Intervention

Both higher protein (HP) and lower carbohydrate (LC) diets may promote satiety and enhance body weight (BW) loss. This study investigated whether HP can promote these outcomes independent of carbohydrate (CHO) content. 121 women with obesity (BW: 95.1 ± 13.0 kg, BMI: 35.4 ± 3.9 kg/m2) were randomised to either HP (1.2 g/kg BW) or normal protein (NP, 0.8 g/kg BW) diets, in combination with either LC (28 en%) or normal CHO (NC, 40 en%) diets. A low-energy diet partial diet replacement (LEDpdr) regime was used for 8 weeks, where participants consumed fixed-energy meal replacements plus one ad libitum meal daily. Four-day dietary records showed that daily energy intake (EI) was similar between groups (p = 0.744), but the difference in protein and CHO between groups was lower than expected. Following multiple imputation (completion rate 77%), decrease in mean BW, fat mass (FM) and fat-free mass (FFM) at Week 8 in all was 7.5 ± 0.7 kg (p < 0.001), 5.7 ± 0.5 kg (p < 0.001), and 1.4 ± 0.7 kg (p = 0.054) respectively, but with no significant difference between diet groups. LC (CHO×Week, p < 0.05), but not HP, significantly promoted postprandial satiety during a preload challenge. Improvements in blood biomarkers were unrelated to LEDpdr macronutrient composition. In conclusion, HP did not promote satiety and BW loss compared to NP LEDpdr, irrespective of CHO content.

Macronutrient composition of the diet and long-term changes in weight and waist circumference in the EPIC-Italy cohort

BACKGROUND AND AIMS

The overall macronutrient composition of diet, rather than just calorie intake, may influence long-term changes of anthropometry. We investigated relationships between dietary macronutrient composition and long-term changes in weight and waist circumference in participants of the EPIC-Italy - the Italian section of the European Prospective Investigation into Cancer and Nutrition - study.

METHODS AND RESULTS

A total of 32,119 participants provided anthropometric measures at recruitment and 12 years later (mean). Diet at recruitment was assessed using validated semi-quantitative food frequency questionnaires. Weight and waist changes associated with replacing 10% of energy from one macronutrient with 10% of energy from another macronutrient were assessed by multivariable linear regression. Increased energy from total protein at the expense of any other macronutrient was significantly associated with increased weight and waist circumference. Increased starch at the expense of sugar and total protein was associated with significantly decreased weight and waist circumference; when starch replaced total fat, weight significantly decreased. Increased sugar at the expense of starch and total fat was significantly associated with increased weight and waist circumference; but increase at the expense of total protein was significantly associated with decreased weight and waist circumference.

CONCLUSION

Our results suggest that increasing protein at the expense of fat or carbohydrates, and reducing starch by increasing other macronutrients, might be associated with increased weight and waist gain.

Higher-protein intake improves body composition index in female collegiate dancers

Aesthetic athletes strive to attain an ideal body image and the physical demands placed on dancers make their body composition and fitness equally as important as their technique. Body composition has shown positive changes in response to increased protein intake and may improve aesthetics of dance performance. The purpose of this study was to determine the extent to which supplemental whey protein (PRO) would improve body composition in female collegiate dancers compared with an isocaloric placebo (PLA). Twenty-one (age, 19.6 ± 1.4 years) female collegiate dancers were randomly assigned to consume PRO or PLA (25 g, 3×/day) for 12 weeks. Laboratory testing at weeks 0, 6, and 12 included 24-h urine collection, body composition (dual-energy X-ray absorptiometry), resting metabolic rate, and performance. Data were reported as means ± SD. Significance was accepted at p < 0.05. Body weight, fat mass, and lean soft tissue did not change between groups or over time. Body composition index (BCI = [(LSTpost− LSTpre) + (FMpre− FMpost)]; where LST is lean soft tissue, FM is fat mass, pre is pre-intervention, and post is post-intervention) significantly improved over time in PRO (+0.6 ± 1.9) but not PLA (−1.8 ± 3.1; p = 0.048); however, neither group demonstrated changes in laboratory performance tests. Protein supplementation for 12 weeks significantly improved BCI and provided a simple way to improve the diet in female collegiate dancers.

Novelty Twelve weeks of protein supplementation does not change body weight in female collegiate dancers. BCI improves following protein supplementation in female collegiate dancers.

Sensing and signaling mechanisms linking dietary methionine restriction to the behavioral and physiological components of the response

Dietary methionine restriction (MR) is implemented using a semi-purified diet that reduces methionine by ∼80% and eliminates dietary cysteine. Within hours of its introduction, dietary MR initiates coordinated series of transcriptional programs and physiological responses that include increased energy intake and expenditure, decreased adiposity, enhanced insulin sensitivity, and reduction in circulating and tissue lipids. Significant progress has been made in cataloguing the physiological responses to MR in males but not females, but identities of the sensing and communication networks that orchestrate these responses remain poorly understood. Recent work has implicated hepatic FGF21 as an important mediator of MR, but it is clear that other mechanisms are also involved. The goal of this review is to explore the temporal and spatial organization of the responses to dietary MR as a model for understanding how nutrient sensing systems function to integrate complex transcriptional, physiological, and behavioral responses to changes in dietary composition.

Effects of Resistance Training and Protein Supplementation in Breast Cancer Survivors

PURPOSE

This study aimed to evaluate 12 wk of resistance training (RT; n = 16) and protein supplementation (RT + protein; n = 17) on muscular strength, body composition, and blood biomarkers of muscle (insulin-like growth factor 1 [IGF-1]), fat (adiponectin), and inflammation (human C-reactive protein [CRP]) in breast cancer survivors (BCS).

METHODS

Thirty-three BCS (59 ± 8 yr) were measured pre- and posttraining for one-repetition maximum (1-RM) muscular strength (chest press and leg extension), body composition (lean mass [LM] and fat mass [FM]) via dual-energy x-ray absorptiometry, and serum concentrations of IGF-1, adiponectin, and CRP. RT consisted of 2 d·wk using 10 exercises for two sets of 10-12 repetitions and a third set to failure at ~65%-85% of 1-RM. RT + protein consumed 20 g of protein twice a day. ANOVA was used for analyses. Significance was set at P ≤ 0.05.

RESULTS

Average RT intensity was 65%-81% of 1-RM and was not different between RT and RT + protein. There were no group-time interactions for strength, LM, FM, and biomarkers. Both groups significantly increased upper (+31 ± 18 kg) and lower (+19 ± 12 kg) body strength, LM (+0.9 ± 1.0 kg) and decreased FM (-0.5 ± 1.2 kg), and percent body fat (-1.0% ± 1.2%). Serum levels of IGF-1 significantly increased from baseline to 12 wk in both RT (102 ± 34 to 115 ± 33 ng·mL) and RT + protein (110 ± 40 to 119 ± 37 ng·mL); adiponectin and CRP did not change.

CONCLUSIONS

Twelve weeks of RT at 65%-81% of 1-RM, 2 d·wk in BCS, was well tolerated and significantly improved strength, body composition, and IGF-1. Supplemental protein (40 g·d) did not induce a change in any variable. However, on the basis of food logs, reductions in total calories and dietary protein intake from whole foods resulted in only a net protein increase of 17 g·d for RT + protein, which may have influenced the results.

Protein supplements after weight loss do not improve weight maintenance compared with recommended dietary protein intake despite beneficial effects on appetite sensation and energy expenditure: a randomized, controlled, double-blinded trial

Background: High-protein diets increase weight loss (WL) during energy restriction; therefore, it has been suggested that additional protein intake may improve weight maintenance (WM) after WL.Objective: We investigated the effect of protein supplements from either whey with or without calcium or soy on WM success after WL compared with that of a control.Design: In a randomized, controlled, double-blinded trial, 220 participants aged 18-60 y with body mass index (in kg/m²) from 27.6 to 40.4 were included. The study was initiated with an 8-wk WL period followed by a 24-wk WM period. During WM, participants consumed the following isocaloric supplements (45-48 g/d): whey and calcium (whey+), whey, soy, or maltodextrin (control). Data were collected at baseline, before WM, and after WM (weeks 0, 8, and 32, respectively) and included body composition, blood biochemistry, and blood pressure. Meal tests were performed to investigate diet-induced-thermogenesis (DIT) and appetite sensation. Compliance was tested by 24-h urinary nitrogen excretion.Results: A total of 151 participants completed the WM period. The control and 3 protein supplements did not result in different mean ± SD weight regains (whey+: 2.19 ± 4.6 kg; whey: 2.01 ± 4.6 kg; soy: 1.76 ± 4.7 kg; and control: 2.23 ± 3.8 kg; P = 0.96), fat mass regains (whey+: 0.46 ± 4.5 kg; whey: 0.11 ± 4.1 kg; soy: 0.15 ± 4.1 kg; and control: 0.54 ± 3.3 kg; P = 0.96), or improvements in lean body mass (whey+: 1.87 ± 1.7 kg; whey: 1.94 ± 1.3 kg; soy: 1.58 ± 1.4 kg; and control: 1.74 ± 1.4 kg; P = 0.50) during WM. Changes in blood pressure and blood biochemistry were not different between groups. Compared with the control, protein supplementation resulted in higher DIT (∼30 kJ/2.5 h) and resting energy expenditure (243 kJ/d) and an anorexigenic appetite-sensation profile.Conclusion: Protein supplementation does not result in improved WM success, or blood biochemistry after WL compared with the effects of normal dietary protein intake (0.8-1.0 g · kg^-1 · d^-1). This trial was registered at clinicaltrials.gov as NCT01561131.

Markers of dietary protein intake are associated with successful weight loss in the POUNDS Lost trial

To assess the association of markers for dietary protein intake, measures of dietary adherence and demographic variables with weight loss in the POUNDS Lost study over the first 6 months and again between 6 and 24 months using data from those who completed each period. This is a secondary analysis of pooled data on completers assigned to one of four diets: 65%C/15%P/20%F (AP/LF), 55%C/25%P/20%F (HP/LF), 45%C/15%P/40%F (AP/HF) or 35%C/25%P40%F (HP/HF) in the POUNDS Lost study. Urinary nitrogen excretion, dietary adherence measured by 24-h recall and attendance at sessions, age (above and below 50 years), gender, race/ethnicity and activity by pedometry were analysed. Increased spread between protein intake at baseline and protein at 6 or 24 months, assessed by urinary nitrogen excretion, was associated with greater weight loss from baseline to 2 years. At 6 and 24 months, older age, male gender, body mass index > 30 kg m-2 and adherence to the fat and protein diets were associated with more weight loss. None of these variables was associated with a regain from 6 to 24 months. Weight regain for women in the highest carbohydrate (65%) group was significantly greater (-4.4 kg [95% CI: -5.9, -3.0]) than for women in the lowest carbohydrate group (-1.8 kg [95% CI: -3.2, -0.4 kg]) (P for interaction = 0.012). An increased spread in the difference between baseline and follow-up protein intake was associated with greater weight loss, consistent with the 'protein spread theory'. Women eating the highest carbohydrate diet regained more weight from 6 to 24 months.

Meatballs with 3% and 6% dietary fibre from rye bran or pea fibre - Effects on sensory quality and subjective appetite sensations

This study investigated dose-response effects of rye bran and pea fibre added to meatballs on sensory quality and subjective appetite sensations. Pea fibre or rye bran was added to meatballs in doses ranging from 3g to 6g dietary fibre per 100g. In a sensory profile, a trained panel (n=9) evaluated the meatballs in terms of odour, appearance, texture and flavour attributes. In a cross-over appetite study, 27 healthy men were served five test meals. Subjective appetite sensations were assessed over a 4-hour period. The addition of rye bran to the meatballs increased the grainy odour, texture and flavour. Pea fibre resulted in a more crumbly, firm and gritty texture with increasing doses of fibre. The sensory changes followed a dose-response relationship. Subjective appetite sensations were not affected by the addition of fibre.

Effect of a high protein diet and/or resistance exercise on the preservation of fat free mass during weight loss in overweight and obese older adults: a randomized controlled trial

BACKGROUND

Intentional weight loss in obese older adults is a risk factor for accelerated muscle mass loss. We investigated whether a high protein diet and/or resistance exercise preserves fat free mass (FFM) during weight loss in overweight and obese older adults.

METHODS

We included 100 overweight and obese adults (55-80 year) in a randomized controlled trial (RCT) with a 2 × 2 factorial design and intention-to-treat analysis. During a 10-week weight loss program all subjects followed a hypocaloric diet. Subjects were randomly allocated to either a high protein (1.3 g/kg body weight) or normal protein diet (0.8 g/kg), with or without a resistance exercise program 3 times/week. FFM was assessed by air displacement plethysmography.

RESULTS

At baseline, mean (±SD) BMI was 32 ± 4 kg/m². During intervention, protein intake was 1.13 ± 0.35 g/kg in the high protein groups vs. 0.98 ± 0.29 in the normal protein groups, which reflects a 16.3 ± 5.2 g/d higher protein intake in the high protein groups. Both high protein diet and exercise did not significantly affect change in body weight, FFM and fat mass (FM). No significant protein*exercise interaction effect was observed for FFM. However, within-group analysis showed that high protein in combination with exercise significantly increased FFM (+0.6 ± 1.3 kg, p = 0.011).

CONCLUSION

A high protein diet, though lower than targeted, did not significantly affect changes in FFM during modest weight loss in older overweight and obese adults. There was no significant interaction between the high protein diet and resistance exercise for change in FFM. However, only the group with the combined intervention of high protein diet and resistance exercise significantly increased in FFM.

TRIAL REGISTRATION

Dutch Trial Register, number NTR4556, date 05-01-2014.

The effects of whey protein with or without carbohydrates on resistance training adaptations

Background

Nutrition intake in the context of a resistance training (RT) bout may affect body composition and muscle strength. However, the individual and combined effects of whey protein and carbohydrates on long-term resistance training adaptations are poorly understood.

Methods

A four-week preparatory RT period was conducted in previously untrained males to standardize the training background of the subjects. Thereafter, the subjects were randomized into three groups: 30 g of whey proteins (n = 22), isocaloric carbohydrates (maltodextrin, n = 21), or protein + carbohydrates (n = 25). Within these groups, the subjects were further randomized into two whole-body 12-week RT regimens aiming either for muscle hypertrophy and maximal strength or muscle strength, hypertrophy and power. The post-exercise drink was always ingested immediately after the exercise bout, 2–3 times per week depending on the training period. Body composition (by DXA), quadriceps femoris muscle cross-sectional area (by panoramic ultrasound), maximal strength (by dynamic and isometric leg press) and serum lipids as basic markers of cardiovascular health, were analysed before and after the intervention.

Results

Twelve-week RT led to increased fat-free mass, muscle size and strength independent of post-exercise nutrient intake (P < 0.05). However, the whey protein group reduced more total and abdominal area fat when compared to the carbohydrate group independent of the type of RT (P < 0.05). Thus, a larger relative increase (per kg bodyweight) in fat-free mass was observed in the protein vs. carbohydrate group (P < 0.05) without significant differences to the combined group. No systematic effects of the interventions were found for serum lipids. The RT type did not have an effect on the adaptations in response to different supplementation paradigms.

Conclusions

Post-exercise supplementation with whey proteins when compared to carbohydrates or combination of proteins and carbohydrates did not have a major effect on muscle size or strength when ingested two to three times a week. However, whey proteins may increase abdominal fat loss and relative fat-free mass adaptations in response to resistance training when compared to fast-acting carbohydrates.

Bioactive properties of milk proteins in humans: A review

Many studies have demonstrated that milk protein consumption has benefits in terms of promoting human health. This review assesses the intervention studies which have evaluated potential health enhancing effects in humans following the ingestion of milk proteins. The impact of milk protein ingestion has been studied to asses their satiating, hypotensive, antimicrobial, anti-inflammatory, anticancer, antioxidant and insulinotropic properties as well as their impact on morphological modifications (e.g., muscle and fat mass) in humans. Consistent health promoting effects appear to have been observed in certain instances (i.e., muscle protein synthesis, insulinotropic and hypotensive activity). However, controversial outcomes have also been reported (i.e., antimicrobial, anti-inflammatory, anticancer and antioxidant properties). Several factors including interindividual differences, the timing of protein ingestion as well as the potency of the active components may explain these differences. In addition, processing conditions have been reported, in certain instances, to affect milk protein structure and therefore modify their bioactive potential. It is thought that the health promoting properties of milk proteins are linked to the release of bioactive peptides (BAPs) during gastrointestinal digestion. There is a need for further research to develop a more in-depth understanding on the possible mechanisms involved in the observed physiological effects. In addition, more carefully controlled and appropriately powered human intervention studies are required to demonstrate the health enhancing properties of milk proteins in humans.

A brief review of higher dietary protein diets in weight loss: a focus on athletes

Thermodynamics dictates that for body weight (i.e. stored substrate) loss to occur a person must ingest less energy than they expend. Athletes, who owing to their oftentimes large daily energy expenditures, may have greater flexibility than non-athletes in this regard; however, they may also have different goals for weight loss. In particular, weight lost may be less important to an athlete than from which compartment the weight is lost: fat or lean. A critical question is thus, what balance of macronutrients might promote a greater fat loss, a relative retention of lean mass, and still allow athletic performance to remain uncompromised? It is the central thesis of this review that dietary protein should be a nutrient around which changes in macronutrient composition should be framed. The requirement for protein to sustain lean mass increases while in negative energy balance and protein, as macronutrient, may have advantages with respect to satiety during energy balance, and it may allow greater fat loss during a negative energy balance. However, athletes should be mindful of the fact that increasing dietary protein intake while in negative energy balance would come at the ‘expense’ of another macronutrient. Most recently there has been interest in lower carbohydrate diets, which may not allow performance to be sustained given the importance of dietary carbohydrate in high-intensity exercise. The relative merits of higher protein diets for athletes are discussed.

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.

A high whey protein-, leucine-, and vitamin D-enriched supplement preserves muscle mass during intentional weight loss in obese older adults: a double-blind randomized controlled trial

BACKGROUND

Intentional weight loss in obese older adults is a risk factor for muscle loss and sarcopenia.

OBJECTIVE

The objective was to examine the effect of a high whey protein-, leucine-, and vitamin D-enriched supplement on muscle mass preservation during intentional weight loss in obese older adults.

DESIGN

We included 80 obese older adults in a double-blind randomized controlled trial. During a 13-wk weight loss program, all subjects followed a hypocaloric diet (-600 kcal/d) and performed resistance training 3×/wk. Subjects were randomly allocated to a high whey protein-, leucine-, and vitamin D-enriched supplement including a mix of other macro- and micronutrients (150 kcal, 21 g protein; 10×/wk, intervention group) or an isocaloric control. The primary outcome was change in appendicular muscle mass. The secondary outcomes were body composition, handgrip strength, and physical performance. Data were analyzed by using ANCOVA and mixed linear models with sex and baseline value as covariates.

RESULTS

At baseline, mean ± SD age was 63 ± 5.6 y, and body mass index (in kg/m(2)) was 33 ± 4.4. During the trial, protein intake was 1.11 ± 0.28 g · kg body weight(-1) · d(-1) in the intervention group compared with 0.85 ± 0.24 g · kg body weight(-1) · d(-1) in the control group (P < 0.001). Both intervention and control groups decreased in body weight (-3.4 ± 3.6 kg and -2.8 ± 2.8 kg; both P < 0.001) and fat mass (-3.2 ± 3.1 kg and -2.5 ± 2.4 kg; both P < 0.001), with no differences between groups. The 13-wk change in appendicular muscle mass, however, was different in the intervention and control groups [+0.4 ± 1.2 kg and -0.5 ± 2.1 kg, respectively; β = 0.95 kg (95% CI: 0.09, 1.81); P = 0.03]. Muscle strength and function improved over time without significant differences between groups.

CONCLUSION

A high whey protein-, leucine-, and vitamin D-enriched supplement compared with isocaloric control preserves appendicular muscle mass in obese older adults during a hypocaloric diet and resistance exercise program and might therefore reduce the risk of sarcopenia. This trial was registered at the Dutch Trial Register (http://www.trialregister.nl) as NTR2751.

Dietary protein and urinary nitrogen in relation to 6-year changes in fat mass and fat-free mass

BACKGROUND

In contrast to the physiological expectation, observational studies show that greater protein intake is associated with subsequent body weight (BW) gain. An increase in fat-free mass (FFM) due to the anabolic effects of protein could explain this.

OBJECTIVE

To examine associations between protein intake and subsequent changes in fat mass (FM) and FFM in longitudinal, observational data.

DESIGN

A health examination, including measures of FM and FFM by bioelectrical impedance at baseline and follow-up 6 years later, was conducted. Diet history interviews (DHI) were performed, and 24-h urinary nitrogen collection at baseline was done. In total, 330 participants with DHI, of whom 227 had validated and complete 24-h urine collection data, were analyzed. Macronutrient energy substitution models were used.

RESULTS

Mean estimated protein intake was 14.6 E% from DHI and 11.3 E% from urinary nitrogen. Estimated from DHI, FM increased 46 g per year, with every 1 E% protein substituted for fat (95% confidence interval (CI) = 13, 79; P = 0.006), and FFM increased 15 g per year (1, 30; P = 0.046). Results were similar in other substitution models. Estimated from urinary nitrogen, FM increased 53 g per year, with 1 E% protein substituted for other macronutrients (24, 81; P < 0.0005), and FFM increased 18 g per year (6, 31; P = 0.004).

CONCLUSION

Within a habitual range, a greater protein intake was associated with BW gain, mostly in FM. This is in contrast to the expectations based on physiological and clinical trials, and calls for a better understanding of how habitual dietary protein influences long-term energy balance, versus how greater changes in dietary proteins may influence short-term energy balance.

Long term weight maintenance after advice to consume low carbohydrate, higher protein diets--a systematic review and meta analysis

BACKGROUND

Meta analysis of short term trials indicates that a higher protein, lower carbohydrate weight loss diet enhances fat mass loss and limits lean mass loss compared with a normal protein weight loss diet. Whether this benefit persists long term is not clear.

METHODS AND RESULTS

We selected weight loss studies in adults with at least a 12 month follow up in which a higher percentage protein/lower carbohydrate diet was either planned or would be expected for either weight loss or weight maintenance. Studies were selected regardless of the success of the advice but difference in absolute and percentage protein intake at 12 months was used as a moderator in the analysis. Data was analysed using Comprehensive Meta analysis V2 using a random effects analysis. As many as 32 studies with 3492 individuals were analysed with data on fat and lean mass, glucose and insulin from 18 to 22 studies and lipids from 28 studies. A recommendation to consume a lower carbohydrate, higher protein diet in mostly short term intensive interventions with long term follow up was associated with better weight and fat loss but the effect size was small-standardised means of 0.14 and 0.22, p = 0.008 and p < 0.001 respectively (equivalent to 0.4 kg for both). A difference of 5% or greater in percentage protein between diets at 12 mo was associated with a 3 fold greater effect size compared with <5% (p = 0.038) in fat mass (0.9 vs. 0.3 kg). Fasting triglyceride and insulin were also lower with high protein diets with effect sizes of 0.17 and 0.22, p = 0.003 and p = 0.042 respectively. Other lipids and glucose were not different.

CONCLUSION

The short term benefit of higher protein diets appears to persist to a small degree long term. Benefits are greater with better compliance to the diet.

Protein leverage and energy intake

Increased energy intakes are contributing to overweight and obesity. Growing evidence supports the role of protein appetite in driving excess intake when dietary protein is diluted (the protein leverage hypothesis). Understanding the interactions between dietary macronutrient balance and nutrient-specific appetite systems will be required for designing dietary interventions that work with, rather than against, basic regulatory physiology. Data were collected from 38 published experimental trials measuring ad libitum intake in subjects confined to menus differing in macronutrient composition. Collectively, these trials encompassed considerable variation in percent protein (spanning 8-54% of total energy), carbohydrate (1.6-72%) and fat (11-66%). The data provide an opportunity to describe the individual and interactive effects of dietary protein, carbohydrate and fat on the control of total energy intake. Percent dietary protein was negatively associated with total energy intake (F = 6.9, P < 0.0001) irrespective of whether carbohydrate (F = 0, P = 0.7) or fat (F = 0, P = 0.5) were the diluents of protein. The analysis strongly supports a role for protein leverage in lean, overweight and obese humans. A better appreciation of the targets and regulatory priorities for protein, carbohydrate and fat intake will inform the design of effective and health-promoting weight loss diets, food labelling policies, food production systems and regulatory frameworks.

Dietary protein to maximize resistance training: a review and examination of protein spread and change theories

An appreciable volume of human clinical data supports increased dietary protein for greater gains from resistance training, but not all findings are in agreement. We recently proposed "protein spread theory" and "protein change theory" in an effort to explain discrepancies in the response to increased dietary protein in weight management interventions. The present review aimed to extend "protein spread theory" and "protein change theory" to studies examining the effects of protein on resistance training induced muscle and strength gains. Protein spread theory proposed that there must have been a sufficient spread or % difference in g/kg/day protein intake between groups during a protein intervention to see muscle and strength differences. Protein change theory postulated that for the higher protein group, there must be a sufficient change from baseline g/kg/day protein intake to during study g/kg/day protein intake to see muscle and strength benefits. Seventeen studies met inclusion criteria. In studies where a higher protein intervention was deemed successful there was, on average, a 66.1% g/kg/day between group intake spread versus a 10.2% g/kg/day spread in studies where a higher protein diet was no more effective than control. The average change in habitual protein intake in studies showing higher protein to be more effective than control was +59.5% compared to +6.5% when additional protein was no more effective than control. The magnitudes of difference between the mean spreads and changes of the present review are similar to our previous review on these theories in a weight management context. Providing sufficient deviation from habitual intake appears to be an important factor in determining the success of additional protein in enhancing muscle and strength gains from resistance training. An increase in dietary protein favorably effects muscle and strength during resistance training.