A systematic review and meta-analysis covering 47 studies and more than 3,200 participants found that increased protein intake significantly prevents muscle mass decline in adults with overweight or obesity who are actively losing weight, according to results published in Clinical Nutrition ESPEN.
The analysis found that protein intake exceeding roughly 1.3 grams per kilogram of body weight per day was associated with increased muscle mass retention, while intake below 1.0 g/kg/day was linked with a higher risk of muscle mass decline during a calorie deficit. The current U.S. Recommended Dietary Allowance for protein sits at just 0.8 g/kg/day -- a level researchers note was set to prevent deficiency, not to optimize muscle retention during intentional weight loss.
Separate analysis from the International Weight Control Registry similarly found that higher protein intake predicted leaner body composition among people engaged in active weight-loss attempts, reinforcing the broader pattern across the literature.
Notably, the meta-analysis found enhanced protein intake did not significantly improve muscle strength or physical function -- its measurable benefit was specifically in preserving muscle mass itself, not necessarily functional performance, during the dieting period studied.
Protein's role in preserving lean mass is directly relevant to metabolic rate over the course of a diet, since muscle tissue burns more calories at rest than fat tissue. See our article on protein intake and muscle preservation for a full breakdown of recommended intake ranges.
Sources: Clinical Nutrition ESPEN, International Weight Control Registry / NCBI