GLP-1 drugs shave an average 4.57 kg, and the youngest lose most

GLP-1 receptor agonists have moved from diabetes clinics into mainstream conversation as weight-loss drugs, and new trials keep arriving. That makes it easy to lose track of what the whole body of evidence actually says about how much weight they remove, and for whom. Averages across all the trials matter because individual studies test different drugs, doses and populations. This analysis set out to provide an updated synthesis across weight, body mass index and waist circumference, and to identify which patients appear to benefit most.

The researchers systematically searched three major databases for randomised controlled trials published up to 4 October 2024 that tested GLP-1 receptor agonists in adults with overweight or obesity, with or without diabetes. Trials had to report change from baseline in weight, BMI or waist circumference against placebo. Two reviewers independently searched and extracted the data, resolving disagreements by consensus or a third reviewer. Forty-seven trials qualified, contributing a combined cohort of 23,244 patients, and a meta-regression explored which patient characteristics predicted greater benefit.

Compared with placebo, GLP-1 receptor agonists produced a mean weight reduction of 4.57 kg, a mean BMI reduction of 2.07 kg/m2 and a mean waist circumference reduction of 4.55 cm. The effect was consistent whether or not participants had diabetes, whichever drug was used and however it was administered. The greatest benefit appeared to favour patients who were younger, female, without diabetes, with higher starting weight and BMI but lower baseline HbA1c, and who were treated for longer. The authors note substantial disagreement between trials, partly reflecting deliberately broad inclusion criteria.

This confirms and updates earlier syntheses with newer trials folded in, and the consistency across diabetes status and drug type strengthens the class-wide picture. The waist circumference finding adds something the headline weight number does not, since waist size tracks fat stored around the organs. The meta-regression's profile of who benefits most is suggestive rather than definitive, because it compares across trials rather than within them. How these averages translate to any individual remains an open question.

If you have wondered what these drugs deliver on average rather than in the best-case marketing figures, this is the answer across 47 trials: meaningful but not miraculous reductions in weight and waist size versus placebo. It is also a reason to expect responses to vary, since age, sex, starting weight and treatment duration all appeared to shape the benefit. None of this speaks to whether the drugs suit any particular person; that is a conversation for a clinician.