Weight Regain

Weight regain is what usually happens after weight loss, and the physiology behind it is well characterised. Leptin falls faster than fat mass does, ghrelin rises, resting expenditure sits somewhat below what the new body size predicts, and hunger signalling stays elevated for months to years after the loss. The result is a persistent bias toward restoring the prior weight that operates whether the loss came from diet, drug or surgery, and that does not decay quickly with time spent at the lower weight.

Withdrawal designs quantify it. When semaglutide was stopped after 68 weeks in the STEP 1 extension, participants regained most of the lost weight over the following year and cardiometabolic improvements largely reversed with it. In SURMOUNT-4, participants randomised to continue tirzepatide after a lead-in kept losing weight while those switched to placebo regained substantially. Regain after bariatric surgery is generally slower and less complete, though it is common over a five to ten year horizon.

These results reframe discontinuation as a pharmacological fact rather than a character judgement. A drug whose effect disappears on withdrawal is behaving like an antihypertensive, and that is an argument about treatment duration and coverage, not about willpower. It also means any weight-loss claim without a post-treatment follow-up period is silent on the question that matters most.

Two comparisons are made badly. Regain rates from trials with different withdrawal designs, follow-up lengths and definitions of regain are quoted side by side as though interchangeable. And maintenance protocols, tapers and metabolic reset regimens are marketed as preventing regain when no such approach has demonstrated it in a controlled withdrawal study; the evidence that exists supports continued treatment, which is a different claim entirely.