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The importance of increased plasma free fatty acids (FFAs) in the pathogenesis of insulin resistance in people with prediabetes is unclear. It has been proposed that the increase in plasma insulin associated with obesity should be adequate to suppress adipose tissue lipolytic rates and maintain normal plasma FFA levels. We evaluated serial plasma FFA concentrations for 24 h in 20 adults with obesity and normal fasting glucose and glucose tolerance (metabolically healthy obesity [MHO]) and 20 adults with prediabetes, matched on age, sex, BMI and percent body fat with the MHO group. Insulin sensitivity, assessed as the glucose infusion rate during an insulin clamp, was greater in the MHO than the prediabetes group (48.1±3.0 vs. 23.5±1.3 μmol/kg fat-free mass/min, respectively, P< 0.0001). Plasma FFA were greater throughout 24 h in the prediabetes group than the MHO group (Figure). The 24-h areas under …