Childhood obesity is the next front in the GLP-1 story, and this week brought two pieces of data that together make the picture hard to ignore.
First, Novo Nordisk reported topline results from STEP Young, its phase 3 trial of semaglutide in children aged 6 to younger than 12. Second, a study published in the journal Pediatrics found GLP-1 prescribing among US children with obesity has climbed 310-fold since 2019, even though the absolute numbers remain small. Put together, they show both the potential and the trajectory of these drugs in a population that barely featured in the conversation a few years ago.
What STEP Young found
STEP Young was a randomised, double-blind, placebo-controlled trial involving 165 children with obesity. Participants received once-weekly subcutaneous semaglutide at a maximum dose of 1.7 mg or 2.4 mg (determined by baseline weight) or placebo, with both groups also receiving a reduced-calorie diet and physical activity counselling.
The headline result: at 68 weeks, 40.4% of semaglutide-treated participants had moved below the obesity threshold, compared with 0% in the placebo group. The obesity threshold was defined using age- and sex-specific CDC growth charts as BMI at or above the 95th percentile.
Context matters here. More than 85% of the children in the trial had class II or III obesity at baseline, which is severe obesity. As Ania Jastreboff, professor of medicine and paediatrics at Yale and director of the Yale Obesity Research Center, put it, most of the children were classified as having severe obesity at baseline, yet treatment with semaglutide resulted in a BMI percentile category below the obesity threshold in approximately 40% of the children within about a year of treatment.
The primary endpoint was percentage change in BMI from baseline to week 68, and Novo stated the trial met it. The topline announcement did not release the full mean BMI changes or the between-group treatment difference, so the peer-reviewed paper will be the one to watch for the depth. Follow-up extends to week 104, and the trial is also tracking cardiovascular risk factors, glucose metabolism and body composition.
The prescribing surge
The second data point came from NYU Langone Health, published in the journal Pediatrics on September 4. Using national data, the researchers found that the share of US children aged 8 to 11 with obesity and without diabetes who were prescribed GLP-1 receptor agonists rose from 0.03% in 2019 to 9.3% in 2026, a 310-fold increase within 7.5 years.
During that period, 20,282 children aged 8 to 11 were prescribed GLP-1s. The researchers looked at Saxenda, Wegovy and Zepbound specifically.
A few patterns stand out from the data:
- Prescribing is still rare in absolute terms: 0.6% of young children with obesity versus 0.9% of adolescents.
- Most children prescribed GLP-1s had severe obesity (93.7%).
- Most had at least one obesity-related health issue (65.2%), such as high cholesterol, high blood pressure or sleep apnoea.
- Girls were more likely than boys to receive prescriptions.
Lead investigator Babak Orandi framed it as the first national overview of GLP-1 use in young children: the absolute numbers are still low, but use is accelerating rapidly.
Why this matters for the research community
For people following the peptide and GLP-1 space in Australia, the paediatric angle is worth tracking for three reasons.
First, it extends the evidence window. STEP Young joins a broader STEP programme that already produced data in adolescents, and together they map a dose-response story across age groups. The fact that 0% of placebo children moved below the obesity threshold in STEP Young, while 40.4% of treated children did, is a stark illustration of how little lifestyle intervention alone moves the needle in severe paediatric obesity.
Second, the prescribing data shows what happens when clinical guidelines open a door. US guidelines currently allow GLP-1 use for obesity in children as young as 8, and the prescribing curve has responded accordingly. Whatever one thinks of that policy, it is a signal of how quickly practice follows permission in this space.
Third, the debates that will follow are already visible. Long-term safety data in children is thin, growth and development effects are not fully characterised, and the ethics of weight loss drugs in prepubertal children is a genuinely live public question. These are conversations the Australian community should be prepared for, since paediatric obesity prevalence here follows a similar upward pattern.
What the Research Says
- STEP Young: 40.4% of children aged 6 to <12 with obesity moved below the obesity threshold at 68 weeks on semaglutide plus lifestyle, versus 0% on placebo. N = 165, phase 3, double-blind.
- More than 85% of STEP Young participants had class II or III (severe) obesity at baseline.
- US data in Pediatrics: GLP-1 prescribing for children aged 8-11 with obesity rose from 0.03% (2019) to 9.3% (2026), a 310-fold increase, per NYU Langone.
- Absolute prescribing remains low: 0.6% of young children with obesity were prescribed GLP-1s, most with severe obesity and obesity-related comorbidities.
The caveats
The 40.4% figure came from the trial product estimand, which estimates the treatment effect if all participants adhered to assigned therapy. That is a standard analytical choice in weight loss trials, but it means the headline number assumes full adherence, which real-world use rarely delivers. The intention-to-treat numbers may be lower.
The topline announcement also did not report confidence intervals or the full statistical analysis. The gap between topline and full paper is where important nuance lives, and the GH rule applies here as much as anywhere: wait for the peer-reviewed publication before treating the numbers as settled.
And the prescribing study, for all its scale, measures prescriptions written, not medications taken. Whether those children actually used the drugs, for how long, and what happened to them clinically are separate questions.
The Australian angle
In Australia, none of these drugs are PBS-listed for paediatric obesity, and the regulatory pathway looks different to the US. But the research trajectory is global, and the questions raised by STEP Young and the Pediatrics study will land locally regardless of the PBS status. For anyone in the community who researches GLP-1s or follows the space professionally, the paediatric data is becoming a core part of the conversation rather than a niche aside.
The semaglutide research page has more on the compound’s wider profile, and the Telegram community is a reasonable place to talk through new paediatric data as it lands. As always, this material is for education and research context, not medical guidance.
Sources
Source: Orandi BJ, et al. Pediatrics, published online September 4, 2026. DOI: 10.1542/peds.2026-077048
Source: Novo Nordisk STEP Young topline announcement, September 7, 2026 (as reported by Reuters and GlobeNewswire).
Disclaimer: This article is for educational and informational purposes only. It does not constitute medical advice, therapeutic recommendations, or endorsements of any compound. Grey Highway is a research-education community. We do not sell, supply, or promote the use of research compounds. Always consult a qualified healthcare professional regarding health decisions. For Australian regulatory information, visit the TGA website.