What randomized trials have tested collagen or gelatin supplements for weight loss in adults?
Executive summary
A small but growing set of randomized trials has directly tested collagen or gelatin supplements for effects on body weight or body composition in adults, with several 12‑week randomized, double‑blind, placebo‑controlled trials reporting modest reductions in fat mass or weight in specific populations (older adults or people with overweight/obesity) [1] [2] [3]. However, trials vary widely in collagen type, dose, co‑interventions (exercise or resistance training), sample size and duration, and the evidence is therefore limited and not yet definitive for general weight‑loss recommendations [4] [5] [6].
1. Randomized trials that reported anti‑obesity effects in free‑living adults
A 2024 randomized controlled trial published in Nutrients tested a technologically modified collagen (20 g/day delivered via two protein bars) for 12 weeks in adults with overweight/obesity and reported greater decreases in body weight, BMI, waist circumference, fat mass, fatty liver index and systolic blood pressure versus control (trial details and outcomes summarized in the publication) [1] [7]. Earlier human trials of low‑molecular collagen peptides have also reported reductions in body fat in older adults: a randomized, double‑blind, placebo‑controlled trial tested 15 g/day of collagen peptide for 12 weeks in adults aged ≥50 and reported beneficial effects on body fat control versus placebo [2]. A separate randomized trial of skate‑skin–derived collagen peptides was designed as the first human placebo‑controlled study for body fat reduction in overweight adults and reported tolerability and fat‑loss outcomes, marking one of the early RCTs in this area [3].
2. Trials combining collagen with exercise or testing functional outcomes relevant to body composition
Some RCTs assessed collagen as part of an exercise program rather than as a pure dietary weight‑loss intervention: a randomized controlled trial found that specific collagen peptides combined with resistance training improved body composition and regional muscle strength in premenopausal women or elderly sarcopenic men, suggesting collagen may help preserve or build lean mass during training and thereby influence body composition metrics [3] [1]. The Br. J. Nutr. study of collagen plus resistance training in elderly sarcopenic men is often cited for improved muscle strength and body composition, highlighting that many positive results occur when collagen is an adjunct to exercise rather than a standalone slimming product [3].
3. Acute gelatin/collagen studies on satiety and short‑term intake
Smaller randomized, crossover or short‑term trials have examined gelatin or hydrolyzed collagen for post‑prandial satiety and hunger hormones: a 2009 crossover study of 24 volunteers found that a gelatin breakfast reduced subsequent calorie intake at lunch compared with other proteins in that protocol, and an 8‑subject randomized, double‑blind crossover trial showed that vitamin C‑enriched gelatin raised circulating collagen‑related amino acids and biomarkers after intermittent exercise [8] [9]. These acute studies support potential mechanisms (increased satiety or altered amino‑acid profiles) but are limited by tiny sample sizes and short follow‑up [10] [8].
4. Why the evidence is inconsistent and what the trials do not answer
Systematic reviews and expert summaries note that trial heterogeneity—different collagen forms (gelatin, hydrolysed collagen peptides, marine vs. bovine), doses (from ~5 g single doses up to 20 g/day), co‑interventions (exercise, multinutrient supplements), and small sample sizes—makes it hard to generalize findings to broad adult populations, and larger, longer RCTs are still lacking [4] [5] [6]. Several reviews emphasize that while some RCTs report modest fat‑loss or body‑composition benefits, results are inconsistent across studies and many positive trials involve older adults or exercise programs rather than testing collagen as a standalone weight‑loss agent [11] [5].
5. Bottom line: what randomized evidence exists and what it implies
Randomized evidence includes multiple 12‑week placebo‑controlled trials showing modest reductions in fat mass or weight in selected groups (older adults, people with overweight/obesity) and several acute crossover studies showing satiety or amino‑acid changes after gelatin/collagen intake, plus trials combining collagen with resistance training that improve lean mass or strength [1] [2] [3] [9] [8]. These data justify cautious interest but not broad claims: the evidence is promising in niches (older adults, adjunct to exercise) but remains insufficient to conclude that collagen or gelatin supplements are a reliable weight‑loss therapy for the general adult population, and larger, standardized randomized trials registered on trial registries are still needed [12] [4] [6].