PeptidesInfo

Research area

Metabolic health

This is the one research area where peptide evidence is genuinely established: semaglutide and tirzepatide are FDA-approved on the strength of large randomised trials for type 2 diabetes and weight management. Everything else marketed for metabolism — growth-hormone secretagogues, 'fat-loss' fragments — sits several evidence tiers lower.

Abstract illustration of a peptide chain used as the metabolic health research hub image

Evidence map: peptides studied in this area

How grades work →
PeptideEvidence for this areaRegulatory statusWhat has been studied
SemaglutideEstablished evidenceFDA-approved for this useFDA-approved for type 2 diabetes (Ozempic, Rybelsus), chronic weight management (Wegovy) and cardiovascular risk reduction; supported by the SUSTAIN, PIONEER, STEP and SELECT trial programmes.
TirzepatideEstablished evidenceFDA-approved for this useFDA-approved for type 2 diabetes (Mounjaro) and chronic weight management (Zepbound); SURPASS and SURMOUNT randomised trials.
TesamorelinEstablished evidenceFDA-approved for this useFDA-approved to reduce excess abdominal fat in HIV-associated lipodystrophy; evidence for any other metabolic use is limited and off-label.
CJC-1295Preliminary evidenceNot FDA-approvedSmall human pharmacology studies show it raises GH and IGF-1; no trials of metabolic outcomes.
IpamorelinPreliminary evidenceNot FDA-approvedEarly human pharmacology and one discontinued post-operative ileus programme; no metabolic outcome data.

Grades reflect the strength of evidence for this research area specifically. Definitions: Established, Promising, Preliminary, Preclinical, Unsupported, Conflicting.

The evidence gap inside "metabolic peptides"

Marketing puts semaglutide and growth-hormone secretagogues in the same "metabolic peptide" bucket. The evidence does not. Incretin-based drugs have been tested in tens of thousands of participants in randomised trials with hard outcomes — HbA1c, body weight, cardiovascular events. Growth-hormone secretagogues have been tested in dozens to a few hundred participants, mostly for hormone levels rather than clinical outcomes.

What is established

  • Semaglutide and tirzepatide reduce body weight and improve glycaemic control in randomised placebo-controlled trials lasting more than a year, and both carry FDA approvals for these uses. Semaglutide has also shown reduction in major adverse cardiovascular events in people with established cardiovascular disease and overweight or obesity (SELECT trial).
  • Tesamorelin reduces visceral adipose tissue in people with HIV-associated lipodystrophy and is FDA-approved for that narrow indication.

What is not

  • CJC-1295 and ipamorelin raise growth hormone and IGF-1 in short human pharmacology studies. Whether that changes body composition, insulin sensitivity or anything a patient would notice has not been shown in controlled trials.
  • Claims that GH secretagogues are a "natural" or "safer" alternative to GLP-1 drugs are not evidence-based; the two classes have not been compared, and secretagogues lack the long-term safety data the incretin drugs have accumulated.

Open questions we are tracking

  • Durability of weight loss after stopping GLP-1/GIP therapy (STEP 1 extension and SURMOUNT-4 data show substantial regain).
  • Lean-mass loss during rapid weight reduction and whether resistance training or protein intake mitigates it.
  • Compounded and counterfeit semaglutide/tirzepatide safety, which the FDA has issued warnings about.

Analyses in metabolic health

Comparisons3 min read

Retatrutide vs Tirzepatide vs Semaglutide: How the Trial Results Compare

One target, two targets, three targets: semaglutide, tirzepatide and retatrutide represent three generations of the same drug idea. Here is what their landmark trials actually reported, what can and cannot be compared across them, and where each stands with regulators.

Benefits4 min read

NAD+: What It Is, and What the Human Evidence Actually Shows

NAD+ is sold as drips, shots and supplements for energy and aging. Precursor pills really do raise NAD+ in blood - but the benefit trials are mostly small and mixed, and direct NAD+ infusions have almost no published human data. Here is the honest picture.

Benefits2 min read

Best Peptides for Beginners: Where the Evidence Actually Is

New to peptides? Skip the hyped research chemicals and start where the human evidence is strongest - GLP-1s for weight, collagen for skin and joints, PT-141 for low desire. Here is the honest beginner's map.

Benefits3 min read

Sermorelin: Benefits, Uses, and What the Evidence Shows

Sermorelin nudges your body to make its own growth hormone. It was once FDA-approved for children's growth, and is now used off-label for anti-aging and body composition. The direct human evidence is limited but promising. Here's the honest read.

Research4 min read

Retatrutide: The Triple-Hormone Weight-Loss Drug Still in Trials

Retatrutide is the next-generation weight-loss drug that hits three hormone targets at once. Trial results are striking, but it is not FDA-approved and cannot be legally compounded. Here is what the evidence actually shows.

Benefits4 min read

Peptides for Energy and Sleep: Claims Versus Trials

Better sleep and more energy are standard peptide selling points. No growth-hormone secretagogue has been tested with sleep laboratory measurement, and the one peptide with a large sleep trial works by a completely different route.

Research3 min read

MOTS-c: The 'Exercise in a Molecule' Peptide, Honestly Assessed

MOTS-c is a peptide your own mitochondria make - it rises with exercise and improves metabolism and healthspan in mice. It's genuinely fascinating science. But the evidence for taking it is still preclinical. Here's the honest read.

Regulation4 min read

Compounded Semaglutide: What the FDA Actually Says

Compounded semaglutide is not the same as Ozempic or Wegovy. It is not FDA-checked, the shortage that made it common is over, and the FDA has linked it to dosing errors and hospital visits. Here is the plain version.

Benefits2 min read

Best Peptides for Women: What the Evidence Supports

For women, a few peptides have genuine evidence - collagen for skin and joints, GLP-1s for weight, PT-141 for low desire. Many others are marketed on hope. Here is the honest, goal-by-goal guide.

Benefits2 min read

Best Peptides for Men: What the Evidence Supports

For men, the peptides with real evidence are specific: GLP-1s and tesamorelin for fat, PT-141 and kisspeptin for libido. The muscle and 'anti-aging' peptides are hyped hardest and proven least. Here's the honest guide.

Research3 min read

AOD-9604: The 'Fat-Loss Fragment' Whose Big Trial Failed

AOD-9604 is sold as a fat-loss peptide - a fragment of growth hormone. It works in mice, but its one large human trial failed to beat placebo and was never published. Here is the honest evidence.

Benefits4 min read

Are Peptides Worth It? A Framework for Deciding

Whether a peptide is worth it depends on four things: what benefit is proven, in whom, for how long, and whether the effect lasts after you stop. Here is that framework applied to every peptide we cover.

Benefits8 min read

Peptide Benefits: What the Evidence Actually Supports

Peptides are credited with dozens of benefits. Some are proven in large trials, some are modest and real, and some have never been tested in a person. This is every major benefit claim, sorted by how strong the human evidence is.

Benefits5 min read

GLP-1 Benefits Beyond Weight Loss: Heart, Kidney, Liver, and Sleep

Semaglutide and tirzepatide have now shown benefits in cardiovascular events, kidney disease, liver disease, heart failure and sleep apnoea — each in its own trial, in its own population. Here is what each one actually demonstrated.

Research analysis5 min read

GLP-1 Peptides: Established Uses Versus Emerging Research

Semaglutide and tirzepatide are the best-evidenced peptides in medicine — for specific uses. We separate the approved indications with large trials from the emerging research (kidney, liver, heart failure, sleep apnoea, Alzheimer's) and the open questions about regain, muscle loss and compounded products.

Research analysis5 min read

CJC-1295 and Ipamorelin: Growth Hormone Research and Unanswered Risks

The 'CJC/ipa' stack is sold for muscle, fat loss, sleep and anti-aging. The human evidence is a handful of short hormone-level studies, two abandoned development programmes, and no outcome trials — plus a set of risks that have never been studied because the trials were never run.

Research analysis4 min read

Tesamorelin: Approved Use, Off-Label Interest, and Clinical Evidence

Tesamorelin is the one GHRH analogue that finished phase 3 and won FDA approval — for excess abdominal fat in HIV-associated lipodystrophy. We separate that established evidence from the off-label uses it is now marketed for: general visceral fat, liver fat, and cognition.