Effect of Protein Supplementation During Diet-Induced Weight Loss on Muscle Mass and Strength: A Randomized Controlled Study

Abstract

Objective: High protein (particularly leucine-rich whey protein) intake is recommended to mitigate the adverse effect of weight loss on muscle mass. The effectiveness of this approach is unknown.

Methods: Seventy middle-aged (50-65 years old) postmenopausal women with obesity were randomized to (1) weight maintenance (WM), (2) weight loss and the recommended daily allowance for protein (0.8 g/kg/d) (WL group), or (3) weight loss plus whey protein supplementation (total protein: 1.2 g/kg/d) (WL-PS group). Thigh muscle volume and strength were assessed at baseline and after 5% and 10% weight loss in the weight-loss groups and after matched time periods (∼3 and 6 months, respectively) in the WM group.

Results: A 5% weight loss caused a greater decrease in thigh muscle volume in the WL group than the WL-PS group (4.7% ± 0.7% vs. 2.8% ± 0.8%, respectively; P < 0.05). After 10% weight loss, there was no statistically significant difference in muscle mass loss in the two groups, and the total loss was small in both groups (5.5% ± 0.8% and 4.5% ± 0.7%, respectively). The dietary interventions did not affect muscle strength.

Conclusions: Whey protein supplementation during diet-induced weight loss does not have clinically important therapeutic effects on muscle mass or strength in middle-aged postmenopausal women with obesity.

Trial registration: ClinicalTrials.gov NCT01538836.

Conflict of interest statement

Disclosure: None of the authors had any potential conflicts of interest and no funding entity had any role in the design, implementation, analysis and interpretation of the data.

© 2018 The Obesity Society.

Figures

Figure 1. Changes in body mass during the dietary interventions in subjects who completed all study visits

Data are expressed as mean ± SEM. WL: weight loss (n=18); WL-PS: weight loss and protein supplementation (n=19); WM: weight maintenance (n=16).

Figure 2. Changes in thigh muscle and intermuscular adipose tissue volumes during the dietary interventions in all subjects who completed baseline testing (intention-to-treat analysis)

The left panel shows thigh muscle and intermuscular adipose tissue volumes expressed as mean ± SEM at baseline (black bars) and after 5% (grey bars) and 10% (white bars) weight loss and a matched time period in the weight maintenance group. The right panel shows the corresponding relative changes from baseline expressed as adjusted means with 95% confidence bounds. Differences in the left panel were analyzed by using a linear mixed model. Change values in the right panel were analyzed by using a linear mixed model with the baseline values as a covariate. The multiple imputation technique was used to account for missing values. IMAT: intermuscular adipose tissue. WL: weight loss (n=27); WL-PS: weight loss and protein supplementation (n=25); WM: weight maintenance (n=18). * Value significantly different from the corresponding value at baseline, P < 0.05. † Value significantly different from the corresponding value after 5% weight loss. ‡ Value significantly different from the corresponding value in the WM group, P < 0.05. § Value significantly different from the corresponding value in the WL group, P < 0.05.