Which collagen or gelatin formulations (hydrolysed, native, swelling agents) have been tested for appetite suppression in human RCTs?
Executive summary
Randomized controlled trials in humans have tested hydrolysed collagen peptides and gelatin (a partially hydrolysed form) for effects on appetite and related hormones, with single‑dose and short‑term supplementation studies reporting signals of increased GLP‑1 and insulin and sometimes reduced subsequent intake, but evidence is limited by small samples, short follow‑up and inconsistent formulations [1] [2] [3]. There are no robust human RCTs showing long‑term appetite suppression from native (unhydrolysed) collagen or so‑called “swelling agent” formulations, and several registered trials exist without posted results [4] [5] [6] [7].
1. Hydrolysed collagen peptides have been trialed in short human RCTs
Randomised controlled work has specifically tested collagen peptides (hydrolysed collagen) for appetite outcomes, including a female exercise cohort trial examining collagen peptide supplementation and post‑exercise energy intake that interpreted its findings alongside earlier human gelatin studies that showed effects on satiety hormones [1] [2]. Those RCTs typically used collagen peptides (CP) or hydrolysed formulations administered as single doses or short‑term supplements and reported possible stimulation of satiety‑promoting hormones such as GLP‑1 and insulin [1] [2].
2. Gelatin (partial hydrolysate) — single doses and meal replacements produced the clearest signals
Several human studies using gelatin — technically a denatured/partially hydrolysed form of collagen — reported acute increases in GLP‑1 and insulin after a single ~20 g dose and greater post‑meal GLP‑1 with decreases in ghrelin in diets rich in gelatin compared with casein, and these results have been cited repeatedly when discussing appetite suppression [1] [2]. Older protein‑comparison RCTs used custard supplements to compare multiple proteins and found that gelatin and gelatin plus tryptophan reduced subjective appetite and intake more than several other proteins in that controlled setting, a finding often referenced in industry writeups [8].
3. Native (unhydrolysed) collagen and “swelling agent” formulations lack RCT evidence for appetite effects
Available human RCT literature and reviews emphasize oral collagen is usually hydrolysed before absorption and note that native collagen and gelatin differ in absorption and bioactivity, but direct randomized trials testing unhydrolysed/native collagen or engineered swelling agents for appetite suppression are not reported in the supplied sources, so claims about those formulations cannot be confirmed from the cited records [7] [3]. Clinical trial registries list studies of collagen/gummy formulations and collagen+vitamin C interventions, but those records lack posted results in the material provided here, leaving an evidence gap for many commercial formats [4] [6] [5].
4. Proposed mechanisms tested in humans are hormonal and amino‑acid mediated, but mechanistic endpoints are incompletely measured
Human RCTs and reviews point to plausible mechanisms: gelatin/hydrolysed collagen can raise circulating glycine and deliver collagen‑derived peptides detectable in blood after ingestion, and some studies report rises in GLP‑1 and insulin consistent with increased satiety signaling [3] [1] [2]. However, several trials did not measure a full panel of regulatory hormones (for example PYY and total ghrelin were not consistently assessed), and systematic commentary warns that heterogeneous dosing and short timeframes limit mechanistic clarity [1] [2] [9].
5. Animal evidence suggests anti‑obesity effects but cannot substitute for human RCT confirmation
Preclinical meta‑analyses in rodents report anti‑obesity effects from regular collagen peptide administration under high‑calorie feeding, reinforcing biological plausibility, but these are animal RCTs with different dosing and physiology and therefore do not prove comparable appetite‑suppressant effects in humans [10]. Translational gaps and risk‑of‑bias considerations in animal work are explicitly noted by reviewers [10].
6. Limitations, conflicts and what the literature still does not answer
The human evidence base is dominated by small, short trials using specific hydrolysed collagen peptides or gelatin in single‑dose or brief interventions, with inconsistent measurement of appetite hormones and few long‑term blinded RCTs; industry summaries sometimes overstate older single‑meal findings [1] [2] [8] [9]. Clinical trial registry entries show additional trials exist but lack accessible outcomes in the supplied material, and authoritative reviews flag the overall problem of non‑standardized formulations and small sample sizes [4] [5] [6] [9] [7].
Bottom line: what formulations have been tested in human RCTs for appetite suppression?
Hydrolysed collagen peptides and gelatin (a partially hydrolysed form of collagen) have been tested in human randomized trials and acute meal experiments with signals of increased GLP‑1/insulin and sometimes reduced intake, whereas native (unhydrolysed) collagen and proprietary “swelling agent” formats lack RCT evidence in the provided sources; registered trials exist but many results are not posted or standardized, leaving the question of durable appetite suppression unresolved [1] [2] [8] [3] [4] [5] [6] [7].