GLP-1 medications — the class of drugs behind Ozempic, Wegovy, Mounjaro and Saxenda — have transformed the treatment of obesity and type 2 diabetes in adults, and their use in children and teenagers is growing. But a new study published on September 17, 2026, in the journal Childhood Obesity sounds a note of caution: nearly one in six young patients developed a diagnosed nutritional deficiency within a year of starting treatment.
The findings, reported this week by HealthDay, News-Medical and other outlets, highlight a less-discussed consequence of appetite-suppressing drugs in growing bodies. Losing weight or controlling blood sugar can also mean eating less — and for adolescents in a period of rapid growth, that gap can matter.
What the study found
Researchers analyzed national administrative health insurance claims collected between 2017 and 2022, covering more than 100 million patients. From that pool they identified 2,031 children and teenagers ages 10 to 17 who had started a GLP-1 receptor agonist, had continuous health coverage and had no previous diagnosis of nutritional deficiency. About 62.6 percent of the group had obesity.
The most commonly prescribed drugs in the group were liraglutide (78.6 percent), dulaglutide (10.4 percent) and semaglutide (9.1 percent) — reflecting prescribing patterns during the study years, before the newest GLP-1 drugs became as widely used.
Within one year of starting treatment, 16.88 percent of the young patients — nearly one in six — had been diagnosed with at least one nutritional deficiency or deficiency-related complication. Vitamin D deficiency was by far the most common, affecting 12.4 percent of the children. Nutritional anemia was diagnosed in 1.55 percent and iron-deficiency anemia in 1.44 percent.
The problems did not take long to appear. Within 180 days of starting treatment, 10.2 percent of patients had already been diagnosed with at least one deficiency or related complication.
Why adolescence is a vulnerable window
"As appropriate pediatric use of GLP-1s becomes more widespread, we need to understand the risks during periods of rapid growth and pubertal development," said senior author Justin Ryder, PhD, vice chair of research for the Department of Surgery at Ann & Robert H. Lurie Children's Hospital of Chicago and associate professor at Northwestern University Feinberg School of Medicine. "Nutrients such as vitamin D, iron and calcium are of particular concern during adolescence, when deficiencies may have lasting implications for skeletal health and overall development."
Adolescence is when the body builds much of its peak bone mass, expands blood volume and undergoes major hormonal changes — all processes that demand a steady supply of micronutrients. GLP-1 medications work in part by reducing appetite and slowing digestion, which can make it harder for young patients to eat enough nutrient-dense food. Vitamin D, in particular, supports calcium absorption and bone mineralization, making shortfalls during the teen years potentially consequential for long-term skeletal health.
Iron matters too. Iron-deficiency anemia can cause fatigue, poor concentration and reduced exercise tolerance — symptoms that are easy to overlook or misattribute in teenagers already adjusting to a new medication.
The counseling gap
Perhaps the study's most actionable finding concerns what did not happen. Despite the apparent risks, nutritional counseling was rare. Only 5 percent of the young patients received nutritional counseling within 30 days of starting GLP-1 treatment, and fewer than 25 percent received it within six months. Within 180 days, just 23.3 percent had a nutrition therapy or counseling visit, with the average wait for a first visit stretching to 149 days.
"Nutritional support needs to play a critical role once treatment with a GLP-1 medication is initiated," Ryder said. "In our study, however, we found that only 5% of patients received nutritional counseling within 30 days of GLP-1 treatment and less than 25% received nutritional counseling within 6 months."
The researchers suggest that nutritional monitoring and support should begin when GLP-1 treatment starts — not after a deficiency has already developed. Proactive screening could catch problems earlier, when simple dietary adjustments or supplements can correct them.
Important caveats
The study's authors and outside observers note several limitations. The analysis was descriptive and based on insurance claims, so it cannot establish that GLP-1 drugs directly caused the deficiencies. Claims data can miss deficiencies that were never formally diagnosed, and it cannot fully capture what patients were actually eating. It is also possible that some deficiencies predated treatment but were only detected once patients entered closer medical follow-up.
Readers should also know that the study's first author, Kirk W. Kerr, PhD, is affiliated with Abbott Nutrition, a company that sells nutritional products — a potential conflict of interest worth keeping in mind when interpreting the findings, even though the work went through peer review.
None of this means GLP-1 medications have no place in pediatric care. For teenagers with severe obesity or type 2 diabetes, the drugs can deliver meaningful health benefits, and clinical guidelines in several countries now include them as an option alongside lifestyle programs. The study's message is not to abandon these treatments but to pair them with the nutritional oversight that growing bodies require.
What parents and clinicians can do
For families considering or already using a GLP-1 medication for a child, the practical takeaways from the research are straightforward. Ask the prescribing doctor about baseline nutritional screening — particularly vitamin D, iron and calcium status — before or soon after treatment begins. Request a referral to a registered dietitian or nutrition counselor early, rather than waiting for symptoms. Make sure follow-up bloodwork is scheduled, and report fatigue, bone pain, frequent illness or other new symptoms promptly.
Clinicians, for their part, may want to build nutrition checks into the treatment protocol from day one: a dietitian visit at initiation, periodic lab monitoring and clear guidance on protein, fiber, calcium, iron and vitamin D intake while appetite is suppressed.
As with any medication decision for a minor, families should discuss benefits and risks with their child's pediatrician or specialist. This article reports on published research and is not medical advice.
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