Weight gain is often a downside of taking medication to address autism symptoms, but a new study suggests that a commonly-used drug may counteract this unwanted side effect.

Children who took the diabetes drug metformin alongside antipsychotics experienced less weight gain.

That’s the finding of a study published this week in the journal JAMA Psychiatry looking at the experiences of 60 kids with autism ages 6 to 17.

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Over the course of 16 weeks, researchers followed the children, all of whom were overweight as a result of taking the antipsychotic medications. Twenty-eight kids were given metformin and the rest took a placebo.

While those in the placebo group continued to pack on pounds, children in the treatment group saw their body mass index scores decline, the study found. Remarkably, three of those taking metformin saw their BMI measures fall 8 to 9 percent during the four-month study.

Individuals taking metformin did experience a higher number of gastrointestinal issues and five kids stopped taking the drug because of agitation or sedation, but overall researchers said the treatment was well-tolerated.

Currently, the antipsychotics risperidone, sold as Risperdal, and aripiprazole, or Abilify, are the only drugs approved to address symptoms of autism. No medication is designed to treat the core functions of the developmental disorder, however.

“Use of antipsychotics to help manage irritability associated with ASD can sometimes be long­-term, which means we need to provide families with solutions that support lasting optimal health in their children,” said Evdokia Anagnostou of the Holland Bloorview Kids Rehabilitation Hospital’s Autism Research Centre in Toronto who led the study.

The researchers acknowledged that, while promising, their study is small and more research is needed.

“Clearly, Anagnostou et al understand the dilemma our field faces in balancing the risk-benefit ratio of treating youths with ASD with atypical antipsychotics,” wrote Christopher J. McDougle of Massachusetts General Hospital and Harvard Medical School in an accompanying editorial.

“They have identified a potential medication co-treatment to help mitigate the weight gain associated with atypical antipsychotic use in children with ASD. They also realize the limitations of their study.”