What clinical trials exist testing gelatin or collagen supplements for long‑term weight loss?

1. What clinical trials are on the record testing gelatin or collagen for body weight or fat outcomes

A small but growing set of randomized controlled trials and registries have examined collagen or gelatin supplements with endpoints relevant to weight control: a 2024 human randomized controlled trial reported from the University of Navarra tested a native bovine type I collagen powder (registered as NCT05368311) and reported anti‑obesity effects in Nutrients (López‑Yoldi et al.) ^{[4] [5]}. Separate randomized trials of low‑molecular‑weight collagen peptides in older adults (≥50 years) evaluated body‑fat mass over 12 weeks and reported reductions in fat mass compared with placebo (the Kyung Hee University trial summarized in an open‑access paper) ^[6]. Earlier and smaller trials have used gelatine doses (e.g., 5–15 g/day) or hydrolysed collagen peptides in short interventions focused on body composition or satiety (summarized in systematic reviews) ^[2].

2. What these trials actually measured and what they found

The University of Navarra study tested a native collagen with low digestibility and high swelling capacity and reported anti‑obesity effects in a randomized human trial (NCT05368311) ^[4]. The Korean randomized, double‑blind, placebo‑controlled trial in adults aged 50+ ran for 12 weeks and found beneficial effects on body fat control with collagen peptide supplementation ^[6]. Systematic reviews and trial collections show scattered signals that some collagen formulations can reduce appetite or modestly reduce fat mass over weeks to months, and that gelatin in particular sometimes suppresses acute hunger compared with other proteins in controlled feeding tests ^{[2] [7]}.

3. Why these are not “long‑term” weight‑loss trials

Meta‑analyses and recent reviews emphasize that most collagen trials have short durations—mean intervention length across many studies is about 8–12 weeks, with only a few extending to 18–24 weeks—and sample sizes are usually small to moderate, limiting inference about durable weight loss or maintenance ^[1]. The field lacks large, multi‑center RCTs with a year or more of follow‑up, prespecified weight‑loss endpoints, and standardized behavioral controls; leading reviewers explicitly call for long‑term trials with mechanistic biomarkers and standardized endpoints to validate systemic effects ^[1].

4. Quality, heterogeneity and conflicts in the evidence

Trials differ markedly in product (gelatin vs. hydrolysed collagen peptides vs. native undenatured collagen), dose, co‑interventions (some added vitamin C or exercise), and endpoints, producing heterogeneity that complicates pooled conclusions ^{[2] [8]}. Commercial interests and product diversity are implicit drivers of research focus on short‑term biomarker or cosmetic endpoints, and several reviews warn that absorption and bioavailability differ by formulation, meaning effects seen with one collagen type may not generalize to others ^{[9] [2]}.

5. Bottom line and where the evidence must go next

Conclusive evidence that gelatin or collagen supplements produce clinically meaningful, sustained weight loss does not yet exist: randomized trials showing fat‑mass reductions are promising but short, limited in scale, and product‑specific ^{[4] [6] [2]}. Major unanswered questions include durability of weight‑loss effects beyond 12–24 weeks, dose–response relationships across formulations, and whether reported benefits come from satiety effects, altered metabolism, or measurement artefacts; leading reviews and authors explicitly call for larger, longer RCTs with standardized endpoints and mechanistic biomarkers ^{[1] [2]}. Consumer‑facing sources and reviews correctly note that evidence is preliminary and that collagen is not a complete dietary protein nor a proven weight‑loss therapy ^{[3] [10]}.