Accepted answer
The mechanism explains the pattern. Delayed gastric emptying plus central appetite suppression produces early satiety, and early satiety plus a slowed transit produces exactly the symptom cluster people report.
The gallbladder signal tracks the rate of weight loss more than it tracks the drug. Rapid mobilisation of adipose tissue increases biliary cholesterol saturation and reduces gallbladder motility; that combination is lithogenic whether the loss came from a drug, a very-low-energy diet or bariatric surgery. The drug contribution on top of that is present but smaller than the rate contribution.
Gastrointestinal adverse events, indicative pooled rates
| Event | Active arm | Placebo arm | Timing |
|---|
| Nausea | 40–45 % | 15–20 % | Peaks 1–2 wk after each step |
| Vomiting | 15–25 % | 5–8 % | Follows nausea |
| Diarrhoea | 20–30 % | 10–15 % | Early, variable |
| Constipation | 20–25 % | 8–12 % | Later onset, persistent |
| Discontinuation for GI events | 4–7 % | 1–2 % | Mostly during escalation |
Ranges span agents and doses; read the specific prescribing information for a specific figure.
Distinguishing an injection-site nodule from an infection: a nodule is firm, non-tender or mildly tender, not warm, not expanding, and appears within a day or two. Cellulitis is warm, tender, expanding, and often accompanied by systemic features. A sterile abscess sits between the two and is fluctuant. Warmth plus expansion plus fever is the combination that stops being a forum question.
SURMOUNT-1 reported gastrointestinal events as the most frequent adverse events, mostly mild to moderate and mostly during escalation, with discontinuation for adverse events in the single digits per cent[1].
Worth being explicit: nothing here is medical advice, and research-use-only compounds are not approved for human use.
Most of this resolves. The point of knowing the pattern is to recognise the small fraction that does not.
edited 10 Feb 2025 by low_dead_space — added the method parameters
6Does this hold at lower concentrations, or does adsorption dominate? – cake_intact 7 months ago 5Worth flagging that this changed in 2025, so older answers on the site are out of date. – sian_llewellyn 5 months ago add a comment