GLP-1 for Adolescents: What STEP TEENS Showed

The STEP TEENS trial enrolled 201 adolescents aged 12–17 with obesity and tested once-weekly semaglutide 2.4 mg against placebo. The result: a 17% placebo-adjusted reduction in BMI at 68 weeks — actually greater than the effect seen in adult trials. 45% of treated teens dropped below the clinical obesity threshold. Published in NEJM in 2022.

More than 250 million children and adolescents worldwide are projected to have obesity by 2030. Adolescent obesity carries not only the cardiometabolic risks of adult obesity but also distinct developmental consequences: early-onset type 2 diabetes, nonalcoholic fatty liver disease, sleep apnea, orthopedic complications, and significant psychological burden including depression, anxiety, and impaired quality of life.

Until recently, pharmacological options for adolescent obesity were limited: liraglutide (Saxenda, approved for ages 12+), orlistat, and phentermine-topiramate. STEP TEENS demonstrated that semaglutide 2.4 mg produces substantially greater weight reduction than any previously tested adolescent obesity drug, and potentially greater relative efficacy than seen in adults.

Trial Design

STEP TEENS (NCT04102189) was a Phase 3a, double-blind, randomized, placebo-controlled trial conducted at 37 sites internationally from October 2019 through March 2022. It enrolled 201 adolescents (ages 12 to <18) with obesity (BMI at or above the 95th percentile for age and sex) who had at least one obesity-related comorbidity or a BMI of 35 kg/m² or higher.

Participants were randomized to once-weekly subcutaneous semaglutide 2.4 mg or placebo for 68 weeks, plus lifestyle intervention. The trial had a 90% completion rate — 180 of 201 participants completed treatment.

Key Results

A secondary analysis showed nearly half (45%) of adolescents on semaglutide lost enough weight to drop below the clinical cutoff for obesity entirely. Three-quarters (74%) improved by at least one BMI category. These results are remarkable in a population where prior drug options produced modest single-digit-percentage weight changes.

Safety in Adolescents

The adverse event profile was similar to adults: gastrointestinal events (nausea, vomiting, diarrhea) were most common, occurring predominantly during dose escalation and rated as mild to moderate. Serious adverse events were uncommon and balanced between groups. No safety signals unique to the adolescent population were identified during the 68-week treatment period.

However, the long-term safety profile in growing adolescents — effects on linear growth, bone mineral density, pubertal development, and body composition during critical developmental windows — remains an open question that cannot be answered by a 68-week trial.