Novo Nordisk released the first top-line results from its STEP Young phase 3 trial this morning, and the headline number is going to be difficult to ignore. After 68 weeks, 40.4% of children ages 6 to under 12 treated with semaglutide were no longer classified as having obesity, compared with 0% of children receiving placebo.
I already know where a lot of people are going to go with this. We are talking about giving a GLP-1 to children as young as 6, and for many people that is going to feel like a bridge too far before they read another word. I understand the hesitation. I have four kids. The idea of putting a young child on a medication that could potentially become long-term treatment is not something I think any parent should take lightly. But I also believe severe childhood obesity deserves to be treated like the disease that it is, not simply observed until a child becomes an adult.
More than 85% of the children enrolled in STEP Young began the trial with class II or class III severe obesity. In children, obesity is defined using age- and sex-specific BMI percentiles because they are still growing. Class II obesity is defined as a BMI at least 120% of the 95th percentile, while class III is at least 140% of the 95th percentile.
So when you hear about this trial, I would resist the temptation to picture a child who is simply carrying around a few extra pounds and whose parents decided they wanted them thinner. That is not what was studied here. The overwhelming majority of these children entered the study with severe obesity, and in my view, that distinction should be at the center of this conversation.
STEP Young was a randomized, double-blind, placebo-controlled multinational trial involving 165 children between the ages of 6 and under 12. The semaglutide group received a maximum weekly dose of either 1.7 mg or 2.4 mg based on their weight at the beginning of the trial, while the control group received placebo. Children in both groups also received dietary and physical activity interventions.
The primary endpoint was percentage change in BMI from baseline through week 68, and Novo says that endpoint was met, with semaglutide producing a superior reduction in BMI compared with placebo. The company has not yet released the full numerical result for that endpoint in this top-line announcement, so we will need the complete data before we can judge the magnitude of that change.
The secondary finding Novo did disclose is the one that will probably drive most of the attention. Using CDC age- and sex-specific growth charts, 40.4% of children receiving semaglutide improved enough in BMI classification that they were no longer considered to have obesity by week 68. None of the children receiving placebo reached that threshold.
That is not a cosmetic outcome. In a population where more than 85% of participants began with class II or class III obesity, nearly two out of every five treated children moved below the obesity threshold over 68 weeks.
Pediatric obesity trials can sound a little strange if you are accustomed to looking at adult GLP-1 studies, because we tend to talk about adult obesity treatment in terms of percentage body-weight reduction. That framework does not translate cleanly to children. Kids are supposed to grow, and they are supposed to gain weight as they grow. The more useful question is whether their BMI trajectory changes relative to other children of the same age and sex.
There are also supportive secondary endpoints looking at anthropometric measurements, cardiovascular risk factors, glucose metabolism and body composition in a DXA subgroup, with measurements extending through weeks 68 and 104. Those data could ultimately tell us much more about what is happening metabolically and physically than the obesity classification alone, and they were not included in detail in today’s announcement.
Safety is going to be every bit as important as efficacy in how this trial is received. Novo says the overall safety and tolerability profile was consistent with previous pediatric and adult trials of semaglutide and liraglutide, with no new safety concerns identified. The company also says it did not identify safety concerns related to growth or pubertal development. Those are reassuring top-line findings, but I still want to see the details. We need adverse events, discontinuations, gastrointestinal effects, nutritional measures, body composition and longer-term growth data before anyone gets too comfortable.
The full STEP Young results are expected to be presented at ObesityWeek in November, and that should give us a much clearer view of both the efficacy and safety picture.
There is another part of this conversation that I think deserves more attention than it usually gets. People who are skeptical of treating childhood obesity with medication are asking completely reasonable questions. What happens if a child starts semaglutide at 8 years old? How long do they stay on it? What happens through puberty? What happens if they stop? Are there developmental effects that we will not understand for years? Those are legitimate questions, and parents deserve good answers to them.
But skepticism has to run in both directions.
If we know what childhood bullying can do to a child, if we know what years of shame, exclusion and being treated differently because of body size can do during the years when a child is forming their identity, don’t we owe it to them to at least ask whether treating severe obesity earlier could spare them some of that harm?
If a child is already living with severe obesity at 8 or 9 years old, and lifestyle intervention has not been enough to meaningfully alter the trajectory, do we owe it to them to consider treatment before another five or ten years pass?
If obesity is a chronic disease when an adult has it, should we really become less willing to treat it simply because the patient is younger?
Those are not questions I think should be answered casually. But I also do not think the safest position is automatically the one that delays treatment.
For years, our response to childhood obesity has often been some version of watchful waiting wrapped in lifestyle advice. Eat better. Move more. Come back in six months. Then six months becomes a year, and a year becomes five, and eventually that child becomes an adult with the same disease, often with more complications layered on top of it.
I think we have to be willing to ask whether that approach has been as harmless as many would like to believe.
None of this means every child with obesity should be prescribed semaglutide. It does not mean medication should replace nutrition, movement, sleep, family support etc. It certainly does not mean a pharmaceutical intervention should ever be used simply because adults are uncomfortable with a child’s appearance.
It means some children may be living with a serious biological disease that deserves medical treatment in addition to lifestyle support. Just like their adult counterparts, many of whom have stories that also began as children who struggled with obesity.
STEP Young does not answer every question around that possibility. It cannot tell us what decades of treatment beginning in childhood will look like. It cannot tell us which child will benefit most, which child should never receive treatment, or exactly where the balance between benefit and risk ultimately lands.
What it does give us is a result that deserves to change the tenor of this debate. In a trial where more than 85% of participants began with class II or class III obesity, and where both groups received lifestyle modification, more than 40% of the children treated with semaglutide moved below the obesity threshold while none receiving placebo did.
My personally held belief is that childhood obesity should be treated, and I think these results make the argument for earlier intervention harder to dismiss. That does not mean every question is answered. It means we now have to weigh the risks of treatment against the risks of allowing a serious disease to continue unchecked during childhood.
The easy debate is whether giving a 6-year-old a GLP-1 sounds scary. Of course it does. The harder question is whether doing nothing is actually the more compassionate or medically responsible choice for a child already living with severe obesity.
That is the question STEP Young puts in front of us.
