Metformin for Antipsychotic-induced Weight Gain in Adults With Intellectual Disability

Metformin oral, 2000mg/day, for 24 weeks.

Oral placebo for 24 weeks

Participants from both groups will meet a dietician and a diabetes educator at the study start to obtain advice regarding healthy diet, portion size, and meal planning to improve physical health. All participants will be invited to monthly group meetings to learn skills which will help them in a variety of wellness areas such as physical exercises and diet. Attendance in these sessions will be encouraged but not mandatory, and attendance will be recorded. Fidelity with these interventions will be captured using diet and physical activity questionnaires at RCT start, midpoint and end, and end of open label phase.