This is the part of the field where I am least certain, and I would be suspicious of anyone who is very certain in either direction.
The trial evidence is genuinely strong. The long-term evidence does not exist and cannot exist yet. Those two facts have to be held together, and most public argument about adolescent prescribing picks one and ignores the other.
What the trial found
STEP TEENS randomised adolescents aged 12 to under 18 with obesity to semaglutide 2.4 mg weekly or placebo, alongside lifestyle intervention, for 68 weeks.
Mean BMI fell by roughly 16 percent in the treatment group. The placebo group’s BMI rose slightly. Around three-quarters of participants on semaglutide achieved at least a five percent weight reduction, against a much smaller fraction on placebo.
The effect was, if anything, larger than in the equivalent adult trial. Side effects were dominated by nausea, vomiting and diarrhoea — the same profile as adults, at broadly similar rates.
By the standards applied to any other paediatric medication, that is a clearly positive trial.
~16%
Mean BMI reduction at 68 weeks in adolescents on semaglutide 2.4 mg
STEP TEENS, NEJM 2022
12+
Minimum age for the Wegovy adolescent indication
95th
BMI percentile for age and sex required to qualify
What is approved, and from what age
Wegovy — semaglutide — from age 12, for a BMI at or above the 95th percentile.
Saxenda — liraglutide, a daily injection — from age 12.
Zepbound — tirzepatide — adults only, from 18. Trials in adolescents are ongoing, as are those for the next wave of molecules.
Ozempic and Mounjaro are licensed for type 2 diabetes, and paediatric use follows that indication rather than a weight one.
The adult eligibility thresholds and the coverage picture are covered in do you qualify; the paediatric criteria use percentiles rather than absolute BMI because a fixed cut-off is meaningless in a growing child.
The guideline that changed the conversation
The American Academy of Pediatrics published a clinical practice guideline in 2023 that recommended clinicians offer pharmacotherapy to adolescents aged 12 and over with obesity, as an adjunct to intensive lifestyle treatment, and consider bariatric surgery from 13 in severe cases.
The significant word was offer. Previous practice had leaned heavily on watchful waiting — the expectation that children would grow into their weight. The AAP’s position was that this expectation is not supported: paediatric obesity largely persists into adulthood, and delay allows metabolic complications to establish themselves during the years when they do the most cumulative damage.
The guideline drew substantial criticism, some of it from clinicians and some from people concerned about eating disorders and medicalising adolescent bodies. That debate has not resolved.
The genuine unknowns
Worth listing precisely, because vague unease is less useful than specific questions.
Duration. If obesity is chronic and the drug works only while taken — as the regain data strongly suggests — then starting at 13 implies a treatment horizon measured in decades. Nobody has fifty-year safety data because the drugs have not existed that long.
Bone. Peak bone mass is largely accrued during adolescence, and weight loss reduces bone density at any age. Losing substantial weight during the exact window when bone is being laid down is a legitimate concern with limited data behind it. The equivalent adult issue is discussed in GLP-1s through menopause.
Muscle and growth. Adolescents are building lean mass on a schedule. The muscle loss that accompanies rapid weight loss in adults is a different proposition in a body that is supposed to be adding tissue. Protein adequacy and resistance training matter more here, not less.
Nutrition. Eating a fraction of your previous intake during peak growth requires the intake to be considerably better composed. The principles in what to eat on a GLP-1 apply with less margin for error.
Eating behaviour. The interaction between appetite suppression and adolescent body image is genuinely under-studied, and the population being prescribed to overlaps with the population at risk of eating disorders. The adult mood picture is in mood on a GLP-1.
Fertility. Adolescent girls need the same contraception conversation adults do, for the same reason — see what happens to your cycle and the four-week rule. This is an awkward conversation and it is not optional.
Watchful waiting was never the neutral option. It was simply the one where nobody had to write a prescription.
What good practice looks like
Where a family and a clinician decide to proceed, the things that distinguish careful prescribing from careless:
- A specialist paediatric weight management service, not a telehealth questionnaire — the general concerns are in the telehealth business
- Genuine intensive lifestyle support alongside, which is what the trial actually tested
- Screening for eating disorders before starting and monitoring during
- Growth, puberty and development tracked on centiles
- Protein intake and resistance training treated as core rather than optional — see protein on a GLP-1
- Micronutrient monitoring, given reduced intake during growth
- The adolescent involved in the decision, not merely subject to it
- Frank discussion of what stopping looks like, before starting — see coming off
Where I land
Reluctantly in favour, in the right hands, for the right adolescent, with real monitoring — and considerably less comfortable about the delivery model than about the drug.
The trial evidence supports the indication. What it does not support is prescribing at scale through platforms that cannot screen for eating disorders, cannot track growth, and will not be there in five years to see what happened. The drug is probably not the risk. The way it reaches teenagers might be.