This study aimed to evaluate if conjugated linoleic acid (CLA) affects insulin sensitivity in healthy overweight and obese. Insulin sensitivity was measured using euglycemic hyperinsulinemic clamp in 41 subjects before and after 6 months supplementation with placebo (olive oil) or CLA (Clarinol™) in a randomized, double blind, placebo‐controlled trial. The median glucose uptake (M) of the CLA group was 6.2 mg kg−1 min−1 (n=24) at baseline, 6.1 mg kg−1 min−1 (n=24) after 6 months, and the median difference was +0.3 mg kg−1 min−1 (n=24). The median M of placebo group was 5.1 mg kg−1 min−1 at baseline and 6.0 mg kg−1 min−1 after 6 months and the median difference was −0.1 mg kg−1 min−1 (n=17). No significant differences were found within or between groups. Likewise, glucose uptake divided by insulin concentration during clamp (M/I), and HOMA and QUICKI derived from fasting glucose were all independent of treatment and time. Change in glucose uptake was inversely correlated to change in HbA1c (p=0.002), weight (p=0.04) and BMI (p=0.04). Change in M/I was inversely correlated to change in weight and BMI.