Effect of dietary fish oil on body fat mass and basal fat oxidation in healthy adults

To investigate whether the substitution of fish oil for visible fats in a control diet (52% carbohydrates, 16% protein, 32% fat; P:S 0.2) influences body fat mass and substrate oxidation in healthy adults. Six volunteers (5 men; 23 +/- 2 y; BMI: 21.9 +/- 1.6) were fed a control diet (C) ad libitum during a period of three weeks and, 10-12 weeks later, the same diet where 6 g/d of visible fat were replaced by 6 g/d of fish oil (FO) for another three weeks. Energy intakes (IKA-calorimeter) were unchanged. Body fat mass (Dual-energy X-ray absorptiometry) decreased with FO (-0.88 +/- 0.16 vs -0.3 +/- 0.34 kg; FO vs C; P < 0.05). When adjusted for lean body mass (Ancova), resting metabolic rate (indirect calorimetry) was unchanged. Basal respiratory quotient decreased with FO (0.815 +/- 0.02 vs 0.834 +/- 0.02; P < 0.05) and basal lipid oxidation increased with FO (1.06 +/- 0.17 vs 0.87 +/- 0.13 mg kg(-1) min(-1); P < 0.05). Dietary FO reduces body fat mass and stimulates lipid oxidation in healthy adults.