Peptide basics

The adolescent GLP-1 trial enrolled 201 people. The adult one enrolled 1,961

This page describes what trial evidence exists for GLP-1 compounds in adolescents. It is not advice about whether anyone should take anything, and contains no dose, schedule or route.

What the trial was

The registry record describes a phase 3, randomised, double-masked study of semaglutide in adolescents with overweight or obesity. It enrolled 201 participants aged 12 to 17, started on 7 October 2019, and reached primary completion on 25 March 2022.¹

Entry did not use a fixed BMI. It required a BMI at or above the 95th percentile for age and sex, or at or above the 85th percentile with a weight-related condition, following the standard growth charts.¹³

The size difference is the point

STEP 1 enrolled 1,961 adults. The adolescent trial enrolled 201. That is roughly one participant in ten, and it means every estimate drawn from the adolescent trial carries a much wider band of uncertainty around it.¹²

It also means subgroups within the adolescent trial — by sex, by age band, by baseline severity — are small enough that little can be said about them with confidence. The trial was sized to answer one question about the whole group.¹

Why results in adults do not simply transfer

The adult trials enrolled people with a mean age in the forties. Adolescents differ in body composition, in hormonal environment, and in the trajectory they are on — a fixed body mass index means something different at 14 than at 46.²³

That is precisely why a separate trial was required rather than an extrapolation from the adult programme, and why the existence of one trial should be read as the beginning of an evidence base rather than a settled one.¹

Common questions