GLP-1 drugs, honestly — what’s proven and what isn’t

These are powerful prescription medicines with real, trial-proven benefits and real risks. This page is education, not medical advice — any decision about them belongs with your own clinician.

What they are

GLP-1 receptor agonists mimic a gut hormone (GLP-1) your body releases after eating. Semaglutide is sold as Ozempic (diabetes) and Wegovy (weight); tirzepatide (Mounjaro / Zepbound) is a dual GIP/GLP-1 agonist. They are given as a weekly injection (an oral semaglutide also exists).

How they work

They slow how fast the stomach empties, increase fullness and reduce appetite (including "food noise"), and — glucose-dependently — nudge insulin up and glucagon down. The result is people eat less without white-knuckle willpower, and blood sugar improves.

How much weight, in the trials

How much weight, in the trials — an illustrative chart on this page. Figures use honest, cited or clearly-illustrative data; they are visual aids, not personal measurements.

What’s actually proven

These are large, high-quality randomised trials.

• Substantial, real weight loss — Semaglutide 2.4 mg produced ~15% average body-weight loss over 68 weeks (STEP 1); tirzepatide reached up to ~20% at the highest dose over 72 weeks (SURMOUNT-1) — far beyond older drugs. (established)
• Better type-2 diabetes control — They meaningfully lower HbA1c and were first approved for type-2 diabetes; the weight and glucose benefits reinforce each other. (established)
• Fewer cardiovascular events — In SELECT, semaglutide cut major cardiovascular events by ~20% in people with obesity and heart disease but no diabetes — a benefit beyond weight alone. (established)
• Kidney and other organ benefits — Trials suggest kidney-protective effects and benefits in conditions like sleep apnea and fatty liver are emerging — promising, still being mapped. (emerging)

The real risks & trade-offs

These are not "free" drugs — the downsides are real.

• Gut side effects — Nausea, vomiting, constipation and reflux are common, especially when escalating the dose. They usually ease over time, and slower titration helps. (established)
• Muscle (lean-mass) loss — A meaningful share of the weight lost is muscle, not just fat. This matters for long-term health and metabolism — adequate protein and resistance training while on the drug are important, not optional. (established)
• Gallstones; rare pancreatitis — Rapid weight loss raises gallstone risk; pancreatitis is uncommon but recognised. Severe, persistent abdominal pain needs urgent medical review. (established)
• Thyroid warning (contraindication) — A rodent signal for thyroid C-cell tumours means they are contraindicated in people with a personal or family history of medullary thyroid cancer or MEN2. Human risk is unconfirmed, but the contraindication stands. (note)
• Weight regain if you stop — This is a chronic treatment: stopping typically regains much of the lost weight as appetite returns. That reframes it as an ongoing medicine, not a short course. (established)

The honest nuances

• “It’s cheating / effortless” — It removes much of the appetite fight, but food quality, protein and training still decide how healthy the result is — especially for preserving muscle. (hype)
• Compounded / grey-market versions — Unregulated compounded or online "semaglutide" carries real risks — wrong dose, impurities, and documented harm. If used at all, it should be a genuine, monitored prescription. (hype)
• “It fixes everything” (alcohol, addiction, aging) — There are intriguing early signals on alcohol and other reward-driven behaviours, but these are not established uses. Interesting to watch, not a reason to take it. (emerging)

What we still don’t know

• Very-long-term (decades) safety The big outcome trials run a few years. Multi-decade safety in people who take these for life is genuinely not yet known.
• Optimal duration — and who regains We don’t know the best length of treatment, whether some people can taper successfully, or how to predict who regains weight.
• Muscle and bone over years How to best preserve lean mass and bone density over long-term use is an active question — protein and strength training are the current best answer.
• The breadth of "off-target" benefits Effects on addiction, cognition and other conditions are under study; today they are hypotheses, not indications.

Who they’re for

They are approved for type-2 diabetes and for obesity (typically a BMI threshold, or a lower one with weight-related conditions). Whether they are right for a given person — and which one, at what dose, alongside what lifestyle plan — is a clinical decision, weighing benefits, risks, cost and access.

Key terms

• GLP-1 A gut hormone released after eating that increases fullness and helps regulate blood sugar; these drugs mimic it.
• GIP A second incretin gut hormone; tirzepatide activates both GIP and GLP-1 receptors.
• Semaglutide The GLP-1 drug sold as Ozempic (diabetes) and Wegovy (weight).
• Tirzepatide A dual GIP/GLP-1 drug sold as Mounjaro / Zepbound.
• MACE Major adverse cardiovascular events — heart attack, stroke or cardiovascular death, the endpoint in outcome trials.
• Lean mass Muscle and other non-fat body tissue; some is lost with rapid weight loss unless protected.