Metabolic Rate Enhancement
What human studies show about peptides and resting metabolic rate. Growth hormone raises it in GH-deficient adults; as of October 2026, no research peptide has a measured effect.
Introduction
Resting metabolic rate is the largest part of daily expenditure. As of October 2026, no human study has shown a lasting rise from any research peptide; the 5-15% figures quoted online have no source. See the thermogenesis overview.
Metabolic Rate Components
| Component | Contribution | Modifiable by Peptides |
|---|---|---|
| Basal metabolic rate | 50-70% | GH replacement only |
| Thermic effect of food | 5-15% | Not studied |
| Physical activity | The rest | Not studied |
Peptide Effects on Metabolism
GH-Related Peptides
| Peptide | Metabolic Effect | Mechanism |
|---|---|---|
| Ipamorelin | Not measured | GH-mediated lipolysis |
| CJC-1295 | Not measured | Sustained GH elevation |
| Tesamorelin | Weight neutral; prescription medicine for HIV-associated abdominal fat | Visceral fat specific |
| AOD-9604 / Fragment 176-191 | No weight benefit in oral and IV trials | Lipolytic in rodents |
FDA's 2024 reviews cite no human fat-loss data for CJC-1295 or ipamorelin; ipamorelin's only efficacy trial (postoperative ileus) failed. AOD-9604 missed its weight endpoint in the OPTIONS trial, and FDA found no human data for injected use (AOD-9604 trial history).
Mitochondrial Peptides
| Peptide | Metabolic Effect | Mechanism | Evidence |
|---|---|---|---|
| MOTS-c | Less diet-induced obesity in mice | AMPK activation | Emerging |
| SS-31 | Cellular energy | Mitochondrial efficiency | Moderate |
SS-31 (elamipretide) has FDA accelerated approval as Forzinity (September 2025) for Barth syndrome only. It isn't approved for weight loss or metabolism. The MOTS-c analog CB4211 was dropped after one 4-week trial.
Timing for Metabolic Enhancement
Users report GH secretagogues fasted in the morning or before bed, sometimes 30 min before exercise. None of these timings has been tested.
Supporting Factors
| Factor | Effect | Notes |
|---|---|---|
| Muscle mass | Higher BMR | Resistance training |
| Protein intake | TEF increase | Highest macronutrient after alcohol |
| Cold exposure | Thermogenesis | See brown fat activation |
Realistic Expectations
| Intervention | Metabolic Increase | Notes |
|---|---|---|
| GH replacement, GH-deficient adults (1989) | About 15% at 1 month, 6% at 6 months | Prescription GH |
| MK-677 25 mg daily, men with obesity (1998) | At 2 weeks only | Fat unchanged |
| Research GH peptides | Not measured |
Neither trial studied healthy users.
What We Still Don't Know
Nobody has tested whether a GH secretagogue keeps metabolic rate raised past a few weeks in healthy adults.
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References
- Growth hormone replacement, body composition and basal metabolic rate in GH-deficient adults (New England Journal of Medicine, 1989; PubMed)
- Two-month MK-677 treatment in obese men: GH secretion, fat-free mass and energy expenditure (Journal of Clinical Endocrinology & Metabolism, 1998; PubMed)
- Diet induced thermogenesis, Westerterp (Nutrition & Metabolism, 2004; PMC)
- Physical activity and physical activity induced energy expenditure in humans, Westerterp (Frontiers in Physiology, 2013; PubMed)
- AOD-9604 briefing document, Pharmacy Compounding Advisory Committee (FDA, December 2024)
- Pharmacy Compounding Advisory Committee transcript including ipamorelin (FDA, October 29, 2024)
- Pharmacy Compounding Advisory Committee transcript including CJC-1295 (FDA, December 4, 2024)
- Egrifta WR (tesamorelin) prescribing information (DailyMed, accessed October 2026)
- FDA grants accelerated approval to first treatment for Barth syndrome (FDA press release, September 19, 2025)
- The mitochondrial-derived peptide MOTS-c promotes metabolic homeostasis and reduces obesity and insulin resistance, mouse study (Cell Metabolism, 2015; PubMed)
- CohBar topline results of the Phase 1a/1b CB4211 study (SEC filing, August 2021)
- CohBar quarterly report note on CB4211 formulation and merger (SEC filing, 2023)