HealthDay News — When combined with a lifestyle intervention, the diabetes drug metformin achieved only short-lived, modest weight loss in obese children and teens without diabetes, findings from a metaanalysis indicate.

The largest metformin-associated benefit observed was a -1.38 BMI reduction (95% CI minus 1.93-minus 0.82; I2, 44%) in a pooled estimate of seven six-month trials when the medication was combined with a lifestyle intervention compared with lifestyle intervention alone, according to Marian S. McDonagh, PharmD, of Oregon Health & Science University in Portland, and colleagues.

Pooled analysis indicated a maximum reduction in BMI of 1.4 kg/m2 in metformin-treated children in studies with durations of 6 to 12 months, they reported in JAMA Pediatrics.

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“Given that the mean BMI at our study outset was 33, this reduction was only 3.6% greater than lifestyle interventions (mean change from baseline in these groups was close to zero), less than the 5% to 10% goals often cited as a marker for meaningful weight loss,” the researchers wrote. “Similarly, weight change was 3.77 kg (8.3 pounds) in studies limited to 6 months.” 

With obesity on the rise among teens and kids, off-label use of metformin to treat childhood obesity has also increased. The drug is currently approved for type 2 diabetes in children aged 10 years and older.

To examine the safety and effectiveness of metformin to treat childhood obesity, McDonagh and colleagues performed a systematic review of 14 clinical trials published between 1996 and 2012. The studies included a total of 946 children and teens ranging from 10 to 16 years, with baseline BMIs of 26 to 41.

At six months there was moderate-strength evidence that metformin was associated with a 1.38 (95% CI: −1.93 to −0.82) reduction in BMI from baseline, compared with control. In studies of less than six months the effect was similar, but lessened; while in studies of one year of treatment, the pooled estimate was not significant.

Smaller, but significant effects were seen in subgroup analyses for those with baseline BMI <35 kg/m², including those of Hispanic ethnicity, those with acanthosis nigricans, those who had failed diet and exercise programs, and in studies with more girls or higher mean age.

No serious adverse events were reported, although moderate-strength evidence indicated more gastrointestinal events with metformin than the control groups (26% vs. 13%; relative risk, 2.05; 95% CI: 1.19 to 3.54).

“Metformin provides a statistically significant, but very modest reduction in BMI when combined with lifestyle interventions over the short term. A large trial is needed to determine the benefits to subgroups or impacts of confounders,” the researchers wrote. “In the context of other options for treating childhood obesity, metformin has not been shown to be clinically superior.”


  1. McDonagh MS et al. JAMA Ped. 2013; doi: 10.1001/jamapediatrics.2013.4200.