What randomized clinical trials exist comparing gelatin or collagen supplements to other proteins for long‑term weight maintenance?
Executive summary
Randomized trials directly comparing gelatin or collagen supplements against other dietary proteins specifically for long‑term weight maintenance are scarce: one published long‑follow up trial is repeatedly cited as the only head‑to‑head 36‑week comparison of gelatin versus milk proteins, while most randomized studies of collagen/gelatin are either placebo‑controlled, short‑term appetite studies, or body‑composition trials in athletes or older adults rather than true long‑term weight‑maintenance trials [1] [2] [3]. The balance of evidence therefore supports modest, short‑term effects on body composition or satiety for some collagen preparations but does not establish a unique advantage for gelatin/collagen over other proteins for sustained weight maintenance [3] [4] [1].
1. What trials actually exist that compare gelatin/collagen to other proteins over the long term?
The most frequently cited randomized head‑to‑head long‑term comparison is a 36‑week randomized controlled trial reported in Physiology & Behavior that compared gelatin with milk proteins for weight maintenance after weight loss; reviewers summarize that both gelatin and milk proteins helped prevent weight regain but found no significant difference between protein types [1]. Beyond that study, there is not a clear set of multiple large, long‑duration RCTs directly comparing gelatin/collagen to other proteins for long‑term weight maintenance in the sources provided [1].
2. What kinds of randomized trials are available, if not long‑term maintenance trials?
Randomized trials in the literature cluster into three types: short acute appetite/preload studies, placebo‑controlled trials of collagen peptides for body‑composition endpoints, and exercise or injury‑related collagen trials. Acute crossover RCTs have directly compared single doses of collagen or whey on appetite and subsequent intake and generally show no consistent superiority of collagen for appetite suppression [4]. Placebo‑controlled 12‑week trials of collagen peptides in older adults report modest reductions in fat mass or preservation of lean mass with daily collagen peptide supplementation, but these compare collagen to placebo rather than other proteins and are short of the “long‑term maintenance” question [2]. Systematic reviews have identified multiple RCTs (fifteen trials in one review) that examine collagen peptides but most address joint pain, muscle recovery, or body composition in athletes rather than sustained weight maintenance [3].
3. What do these trials imply about mechanisms and clinical significance?
Acute studies show that protein preloads including gelatin can increase satiety and reduce short‑term intake in controlled meals, supporting a plausible mechanism for weight maintenance through appetite suppression, but acute effects do not automatically predict durable weight outcomes [4]. Collagen peptides supply specific amino acids (glycine, proline) and some trials report modest favorable shifts in fat mass or lean mass over weeks, particularly when combined with resistance exercise, but collagen’s lower biological value versus whey or casein (fewer branched‑chain amino acids) raises questions about equivalence for muscle‑sparing effects unless doses or co‑interventions differ [2] [5] [3].
4. Gaps, limitations, and conflicting perspectives
Reported trials are heterogeneous in product type (gelatin, hydrolysed collagen, specific bioactive peptides), dose (often ~10–15 g/d), population (athletes, older adults, healthy volunteers), and outcomes (satiety, body composition, collagen synthesis), making cross‑trial conclusions tenuous [2] [3] [6]. The lone longer 36‑week head‑to‑head RCT is useful but insufficient to declare a class effect for gelatin/collagen in long‑term weight maintenance; some reviews and industry summaries highlight potential modest benefits while cautioning that robust large RCTs comparing collagen to high‑quality proteins for sustained weight outcomes are lacking [1] [3] [5]. Additionally, several trials focus on collagen synthesis or joint outcomes (e.g., vitamin C–enriched gelatin before exercise), which are mechanistically interesting but not direct tests of weight maintenance [7] [6] [8].
5. Bottom line for evidence‑based conclusions
The randomized evidence contains short‑term appetite studies and placebo‑controlled trials suggesting modest benefits of collagen/gelatin on satiety or body composition in specific contexts, and a single cited 36‑week randomized comparison that did not show gelatin outperforming milk proteins for weight maintenance, but there is no robust body of large, long‑duration RCTs directly comparing gelatin/collagen to other proteins for sustained weight maintenance in the sources provided [4] [2] [1] [3]. Any definitive claim that gelatin or collagen uniquely supports long‑term weight maintenance over other proteins is not supported by the available randomized trials cited here.