Novo Nordisk said on 7 September 2026 that once-weekly semaglutide reduced body mass index, or BMI, more than placebo in a phase 3 trial involving children aged 6 to under 12 years with obesity. The company said 40.4% of children given semaglutide, assuming full adherence to treatment, were no longer classified as having obesity after 68 weeks, compared with 0% of those who received placebo.
The STEP Young trial included 165 children and met its primary endpoint, which measured the percentage change in BMI from baseline to week 68. The company has yet to disclose the magnitude of the mean BMI reduction in either group. Full results have also yet to be published or peer-reviewed, limiting assessment of the trial beyond the preliminary figures announced by Novo Nordisk.
The study was randomised, double-blind, placebo-controlled and multinational. Such a design means participants were assigned by chance to receive semaglutide or placebo, while the participants and researchers were kept unaware of which treatment each child received.
More than 85% of those enrolled had class II or III severe obesity at the start of the trial. Childhood obesity is defined as BMI at or above the 95th percentile for age and sex. Class II and III obesity are defined as BMI at least 120% and 140% of the 95th percentile respectively.
Children in the treatment group received semaglutide through once-weekly subcutaneous injections. Their maximum dose was either 1.7 mg or 2.4 mg, based on their weight at the start of the study. Both groups also received lifestyle modification throughout the trial, including a reduced-calorie diet and increased physical activity.
The placebo comparison matters because the trial tested semaglutide alongside the same lifestyle measures offered to children who did not receive the medicine. The results therefore indicate that the difference in BMI reduction reported at week 68 was associated with the semaglutide treatment under the conditions of the study.
Novo Nordisk said no new safety concerns emerged during STEP Young. It also said the trial found no safety concerns for growth or pubertal development. The company said the overall safety and tolerability findings were consistent with earlier Novo Nordisk paediatric and adult trials of semaglutide and liraglutide.
The announcement did not set out the specific adverse events in each group, discontinuation rates, or reasons children may have left the study. It also provided no data on whether weight loss was maintained beyond 68 weeks, the trial's secondary endpoints, or adherence to the lifestyle programme.
Semaglutide is the active ingredient in Wegovy and Ozempic. It is not approved for obesity treatment in children under 12. The STEP Young findings are therefore likely to inform debate over medical treatment for younger children with obesity, particularly those with severe disease, while regulatory decisions would require further review.
Martin Holst Lange, Novo Nordisk's Chief Scientific Officer, said: “We are encouraged by the positive STEP Young results and semaglutide's potential to help children living with obesity who need medical treatment, alongside lifestyle changes, to better manage their obesity”.
Detailed STEP Young results are scheduled for presentation at ObesityWeek 2026 in Washington, DC, on 14–17 November 2026. Until those results are available and peer-reviewed, the announced primary-endpoint finding and the proportion of children no longer classified as having obesity, assuming full adherence to treatment, remain the main disclosed measures of the trial's effect.
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