INS and metabolic syndrome: We tested the hypothesis that metformin would blunt metabolic insulin sensitivity and carbohydrate oxidation in an intensity-based manner among adults with metabolic syndrome (MetS) risk.<h4>Materials and methods</h4>In a double-blind, placebo-controlled trial, participants were randomised to low-intensity exercise plus placebo (~55% VO<sub>2</sub>max 5 days/week, LoEx + PL, n = 22) or metformin (2000 mg/day, LoEx + Met, n = 21) and high-intensity exercise plus placebo (~85% VO<sub>2</sub>max 5 days/week, HiEx + PL, n = 24) or metformin (HiEx + Met, n = 24) for 16 weeks.