PURPOSE: Multiple methods have been proposed to assess insulin sensitivity using an oral glucose tolerance test (OGTT), yet the relationship between strength fitness, body composition and the underlying determinants of glycemic control is unclear. We evaluated the associations between muscle strength, body composition and OGTT-derived indices of insulin sensitivity and secretion in young overweight/obese individuals. METHODS: 53 young overweight/obese participants (age 24 ± 5; BMI = 34.5 ± 5.2 kg/m2) underwent a standard 2-hr 75-g OGTT, 1-repetition maximum testing (bench press, leg press, and back row) and body composition by dual-energy X-ray absorptiometry for estimation of total and trunk fat mass and lean body mass (LBM). Fasting glucose (GluT0) and insulin (InsT0), and OGTT-derived indices, including area under the curve for glucose and insulin (AUCGlu and AUCIns respectively), insulinogenic index (IGI; a surrogate measure of first-phase insulin response to a glucose challenge), Matsuda insulin sensitivity index (ISI; a composite of both hepatic and peripheral tissue sensitivity to insulin) and oral disposition index (oral DI; a marker of pancreatic β-cell function) were calculated, and associations between these determinants of glycemic control with muscle strength and body composition were examined. RESULTS: Relative muscle strength, trunk and total fat mass were significantly associated with InsT0 (-0.35, 0.65 and 0.57, respectively), AUCIns (-0.36, 0.63 and 0.56, respectively), IGI (-0.45, -0.61, and 0.64, respectively) and ISI (0.42, -0.54, -0.52, respectively) (all p<0.05), but not with GluT0, AUCGlu or oral DI. There were no significant associations observed between LBM and OGTT-derived indices. CONCLUSION: Strength fitness and fat mass was associated with fasting insulin, AUCIns, early-phase insulin secretion and insulin sensitivity, but not with glucose indices or pancreatic β-cell function in young overweight/obese adults. These findings highlight the potential importance of strength fitness, as opposed to LBM, in protection against the development of type 2 diabetes in overweight/obese population.