Objective: Evaluate the effect of high-oleic and conventional peanuts within a hypocaloric-diet on energy metabolism and body composition. Methods: This 4-week randomized clinical trial included males with BMI of 29.7 6 2.4 kg m 22 and aged between 18 and 50 years. Participants were assigned to the groups: control (CT, n 5 22) that followed a hypocaloric-diet; conventional peanuts (CVP, n 5 22) or high-oleic peanuts (HOP, n 5 21) that received the hypocaloric-diet including (not adding) 56 g day 21 of peanuts. Glucose, fat oxidation, and body fatness and lean mass were the main outcomes. Results: Body weight and composition did not differ between groups. However, within group total body fat (kg) reduced with CVP and HOP, with a significant decrease in body fat percentage in HOP. While total lean mass (kg) decreased in CT, total lean mass (%) increased in HOP. Truncal lean mass decreased in the CT. At baseline, HOP had greater postprandial fat oxidation than the CVP. After 4-weeks, fasting fat oxidation increased in CVP and HOP. Fat oxidation increased in CT and HOP during the 200 min after meal intake compared to the fasting condition. Conclusion: Regular peanut consumption, especially the high-oleic type, within a hypocaloric-diet increased fat oxidation and reduced body fatness in overweigh and obese men.