Protein-Rich Diets for Weight Loss Maintenance

A randomized controlled trial of a weight loss maintenance program in adults with obesity: the WLM3P study

BACKGROUND/OBJECTIVES

The escalating obesity epidemic necessitates effective, sustainable weight loss (WL) and maintenance strategies. This study aimed to evaluate the effectiveness of the Weight Loss Maintenance 3 Phases Program (WLM3P) in achieving a clinically significant long-term weight loss (WL) (≥5% initial WL at 18 months) in adults with obesity compared to a standard low-carbohydrate diet (LCD).

SUBJECTS/METHODS

In this two-phase trial, 112 participants targeting initial WL (0-6 months) and subsequent maintenance (7-18 months) were randomly assigned to either WLM3P or LCD groups. Outcomes assessed included change in body weight (kg, %), improvements in body composition, and metabolic profile.

RESULTS

Of 112 randomized participants, 69% (n = 77) completed the study. At 18 months, WL in the WLM3P group (n = 40) was 15.5 ± 8.3% compared to 9.6 ± 8.5% in the LCD group (n = 37) (p < 0.001). The odds ratio of achieving WL ≥ 10% and ≥15% were significantly higher in the WLM3P group. Complete-case analysis revealed significantly greater improvements in BMI, body fat mass, visceral fat area, waist circumference, waist-to-hip ratio, HDL, and triglyceride/HDL ratio in WLM3P than in LCD. No serious adverse events were reported.

CONCLUSION

Both programs effectively promoted clinically relevant WL and its maintenance. However, the WLM3P program was more successful in helping participants achieve greater WL targets of ≥10% and ≥15%, along with other clinical benefits, after an 18-month intervention.

TRIAL REGISTRATION NUMBER

NCT04192357.

Impacts of dietary animal and plant protein on weight and glycemic control in health, obesity and type 2 diabetes: friend or foe?

It is well established that high-protein diets (i.e. ~25-30% of energy intake from protein) provide benefits for achieving weight loss, and subsequent weight maintenance, in individuals with obesity, and improve glycemic control in type 2 diabetes (T2D). These effects may be attributable to the superior satiating property of protein, at least in part, through stimulation of both gastrointestinal (GI) mechanisms by protein, involving GI hormone release and slowing of gastric emptying, as well as post-absorptive mechanisms facilitated by circulating amino acids. In contrast, there is evidence that the beneficial effects of greater protein intake on body weight and glycemia may only be sustained for 6-12 months. While both suboptimal dietary compliance and metabolic adaptation, as well as substantial limitations in the design of longer-term studies are all likely to contribute to this contradiction, the source of dietary protein (i.e. animal vs. plant) has received inappropriately little attention. This issue has been highlighted by outcomes of recent epidemiological studies indicating that long-term consumption of animal-based protein may have adverse effects in relation to the development of obesity and T2D, while plant-based protein showed either protective or neutral effects. This review examines information relating to the effects of dietary protein on appetite, energy intake and postprandial glycemia, and the relevant GI functions, as reported in acute, intermediate- and long-term studies in humans. We also evaluate knowledge relating to the relevance of the dietary protein source, specifically animal or plant, to the prevention, and management, of obesity and T2D.

Immunomodulatory Effect of Isocaloric Diets with Different Protein Contents on Young Adult Sprague Dawley Rats

To understand the potential mechanisms of dietary protein on intestinal and host health, we studied the immunomodulatory effects of isocaloric diets with high or low crude protein (CP) contents on young adult Sprague Dawley (SD) rats. A total of 180 healthy male rats were randomly assigned to six groups (six replicate pens per treatment with five rats per pen) and fed diets with 10% CP, 14% CP, 20% CP (control), 28% CP, 38% CP, and 50% CP. Compared with the control diet, the rats fed the 14% CP diet significantly elevated lymphocyte cell counts in the peripheral blood and ileum, whereas the 38% CP diet significantly activated the expression of the TLR4/NF-κB signaling pathway in the colonic mucosa (p < 0.05). Moreover, the 50% CP diet reduced growth performance and fat deposition and increased the percentages of CD4⁺ T, B, and NK cells in the peripheral blood and the colonic mucosal expression of IL-8, TNF-α, and TGF-β. Overall, rats fed the 14% CP diet enhanced host immunity by increasing the numbers of immune cells, and the immunological state and growth of SD rats were negatively impacted by the diet containing 50% CP.

Unprocessed red meat in the dietary treatment of obesity: a randomized controlled trial of beef supplementation during weight maintenance after successful weight loss

BACKGROUND

Consumption of unprocessed red meat in randomized trials has no adverse effects on cardiovascular risk factors and body weight, but its physiological effects during weight loss maintenance are not known.

OBJECTIVES

We sought to investigate the effects of healthy diets that include small or large amounts of red meat on the maintenance of lost weight after successful weight loss, and secondarily on body composition (DXA), resting energy expenditure (REE; indirect calorimetry), and cardiometabolic risk factors.

METHODS

In this 5-mo parallel randomized intervention trial, 108 adults with BMI 28-40 kg/m2 (45 males/63 females) underwent an 8-wk rapid weight loss period, and those who lost ≥8% body weight (n = 80) continued to ad libitum weight maintenance diets for 12 wk: a moderate-protein diet with 25 g beef/d (B25, n = 45) or a high-protein diet with 150 g beef/d (B150, n = 35).

RESULTS

In per protocol analysis (n = 69), mean body weight (-1.2 kg; 95% CI: -2.1, -0.3 kg), mean fat mass (-2.7 kg; 95% CI: -3.4, -2.0 kg), and mean body fat content (-2.6%; 95% CI: -3.1, -2.1%) decreased during the maintenance phase, whereas mean lean mass (1.5 kg; 95% CI: 1.0, 2.0 kg) and mean REE (51 kcal/d; 95% CI: 15, 86 kcal/d) increased, with no differences between groups (all P > 0.05). Results were similar in intention-to-treat analysis with multiple imputation for dropouts (20 from B150 compared with 19 from B25, P = 0.929). Changes in cardiometabolic risk factors were not different between groups, the general pattern being a decrease during weight loss and a return to baseline during weight maintenance (and despite the additional mild reduction in weight and fat mass).

CONCLUSIONS

Healthy diets consumed ad libitum that contain a little or a lot of unprocessed beef have similar effects on body weight, energy metabolism, and cardiovascular risk factors during the first 3 mo after clinically significant rapid weight loss.

A protein-supplemented very-low-calorie diet does not mitigate reductions in lean mass and resting metabolic rate in subjects with overweight or obesity: A randomized controlled trial

BACKGROUND & AIMS

The European Food Safety Authority recently recommended an increase in the protein content of total diet replacement (TDR) products from 50 to 75 g/day. The rationale was to minimize reductions in lean mass (LM) and resting metabolic rate (RMR) that occur with weight loss, and thereby facilitate maintenance of lost weight. We sought to directly compare the efficacy of TDR regimens with the new vs the current protein requirement.

METHODS

We randomized 108 adults with overweight or obesity (body mass index 28-40 kg/m²) to very-low-calorie diets (VLCD) with either 52 or 77 g/day protein for 8 weeks (total energy intake of 600 or 700 kcal/day, respectively). LM was determined by dual energy X-ray absorptiometry and RMR by indirect calorimetry.

RESULTS

Attrition rate was 22% in both groups. Both VLCDs decreased body weight, fat mass, LM, and RMR (all P < 0.05). Significant time-by-group interactions were detected for weight and fat mass (both P < 0.05), with corresponding reductions being smaller in the higher-protein than the standard-protein VLCD, likely because of the added calories. On the other hand, reductions in LM (6% from baseline) and RMR (9-10% from baseline) did not differ between groups (P = 0.155 and P = 0.389, respectively), and the contribution of LM to total weight loss was identical (27 ± 2% of lost weight, P = 0.973).

CONCLUSIONS

Our results indicate that the proposed increase in the protein content of TDR products does not attenuate reductions in LM and RMR in individuals with overweight and obesity who are treated with <800 kcal/day VLCDs for 2 months.

CLINICAL TRIAL REGISTRY

ClinicalTrials.gov # NCT04156165.

Understanding the appetite modulation pathways: The role of the FFA1 and FFA4 receptors

Pharmaconutrition is an area of current interest, especially concerning the advances in the pharmacology of nutrient-sensing receptors, as have been accomplished in the last 20 years. The family of free fatty acid (FFA) receptors is composed of four members, sequentially named as FFA1 to FFA4, which are activated by the short to long-chain fatty acids. The affinity of the FFA1 and FFA4 receptors for the omega-3 polyunsaturated fatty acids prompted pre-clinical and clinical investigations regarding their involvement in metabolic diseases. The main studies have been focused on the receptors' expression analyses, the featuring of knockout mice, and the assessment of selective synthetic ligands. These clearly have indicated a relevant role for FFA1 and FFA4 in the peripheral and central circuits for the regulation of energetic metabolism. This review article aimed to discuss the relevance of the FFA1 and FFA4 receptors in appetite-related complications, mainly related to obesity, cancer cachexia, and anorexia in the elderly, emphasizing whether their pharmacological modulation might be useful for the management of these disorders.

The role of dietary protein in obesity

Protein-rich diets are surging in popularity for weight loss. An increase in diet-induced thermogenesis, better preservation of fat-free mass, and enhanced satiety with greater dietary protein intakes may lead to increased energy expenditure and decreased energy intake; and thus promote a more negative energy balance that facilitates weight loss. Results from large randomized trials and meta-analyses of many smaller trials indicate that high-protein diets typically induce significantly greater amounts of weight loss than conventional low-fat or high-carbohydrate diets during the early, rapid weight loss phase (3-6 months), but differences between diets are attenuated and no longer significant during the late, slow weight loss phase (12-24 months). Gradually decreasing adherence may be responsible for this observation; in fact, dietary adherence, rather than macronutrient composition, is likely the major predictor of long-term weight loss success. Recently, some randomized trials evaluated the efficacy of high-protein (vs. normal-protein) diets consumed ad libitum during weight loss maintenance, i.e. after clinically significant weight loss. Weight regain may be smaller with high-protein diets in the short-term (3-12 months), but longer studies are needed to confirm this. Given the lack of conclusive evidence in favor of high-protein diets, or any other dietary pattern, it is reasonable to conclude that no individual nutrient is a friend or a foe when it comes to weight loss and its maintenance. Therefore, any diet that best suits one's dietary habits and food preferences is likely to be better adhered to, and thus lead to more successful long-term weight loss.