Meta-Analysis of 28 Clinical Trials Finds High-Protein Diets Improve Long-Term Weight Maintenance and Preserve Lean Mass

29 September 2026

High-protein diets may modestly improve long-term weight maintenance and preserve lean mass, according to a meta-analysis of 28 randomized clinical trials published in October 2023 in American Journal of Clinical Nutrition. Reviewing studies with 12-month follow-up, the analysis found that higher-protein diets led to an average 1-2 kg loss more than controls, with a "small" effect size. All but one trial showed a superior weight-loss advantage for protein, defined as 25-35% of daily calories or 1.2 to 1.6 g/kg per day.

Fat loss was greater with high-protein diets across studies, while lean mass changes differed insignificantly. A 23 percent increased chance of maintaining lost weight at one year was attributed to benefits such as improved satiety, reduced compulsive eating, and greater adherence. However, the advantage seemed to weaken over time as adherence waned. Another recent review suggests time-limited use (6-12 months) and a switch to a different diet before this.

Critiques of the 2023 analysis point to publication bias favoring positive results, inconsistent protein definitions, and the omission of long-term (>1 year) trial data. Trial funding and Hermann's small-sample 2003 meta-analysis are other disputable factors. Yet, the directionality is clear: across studies, self-reported dietary adherence remained higher in the protein arms. Even a slight increase in protein intake (+100g/day, 10% of total calories) over 12 months improved adherence by 16% per week. "[Higher-protein] trial participants reported lower hunger, better mood, and fewer dietary lapses," says first author Ingrid Van Vliet. She notes that higher protein intake also correlated with fasting-cholesterol improvements, though this was not the primary analysis.

Tulane University Obesity expert Crissy Elkind says that while the evidence can help set personal guidelines, it shouldn't be a basis for personalized nutrition. "Higher protein still needs to fit the patient's cultural and biological factors, and won't work alone for most," Elkind told us. "Lifestyle factors such as physical activity, sleep, and stress-monitoring are more critical when it comes to maintaining needed adaptations following initial weight loss."

For those who can stick it out, a trend of 0.2-1.3 kg/month of additional weight loss may mean keeping up to 0.8-6.8 kg off, on average, after a year on a high-protein diet.