Metformin is known to reduce the risk for T2D in obese adults, but its safety and efficacy in children has been largely unexplored. Deborah Kendall, MD( Department of Paediatric Endocrinology, Royal Manchester Children's Hospital, who led the trial) and co-authors sought to determine whether the medication can benefit obese children by looking at the drug's ability to reduce BMI-SDS(Body Mass Index- Standard Deviation Score). The medicine is not approved for use by obese children or adults in the United Kingdom, but a recent study indicated it has been prescribed for children and youth as an obesity treatment off-label.

"Metformin was associated with a significant reduction in BMI-SDS." "For the 55 participants in each group who contributed to outcome data, mean BMI-SDS changed from +3.44 (SD 0.57) to +3.35 (0.65) in the metformin group, compared with +3.34 (0.5) to +3.31 (0.54) in the placebo group [mean adjusted difference between groups at 6 months was −0.1 SD (95% confidence interval −0.18 to −0.02), P = 0.02]."

Metformin was also associated with lower fasting glucose at 3 months. Fasting glucose dropped from "4.83 (0.46) mmol/liter to 4.79 (0.46) mmol/liter in the metformin group, compared with the placebo group [mean difference: −0.16 mmol/liter (−0.31 to −0.00), P = 0.047]." The authors note, however, that the difference between the 2 groups was not statistically significant at 6 months, even though the drop was maintained.

The treatment appeared safe, with no serious adverse events. Participants in the metformin group, however, reported more adverse events than those in the placebo group (20 vs 8). Most of those adverse events were gastrointestinal issues, which are known adverse effects of metformin in adults.