Dietary supplementation with n-3 PUFA does not promote weight loss when combined with a very-low-energy diet

Obesity is associated with elevated levels of inflammation and metabolic abnormalities which are linked to CVD. The aim of the present study was to investigate whether long-chain n-3 PUFA (LCn-3PUFA), combined with a very-low-energy diet (VLED), facilitated weight loss and weight maintenance, and improvements in blood lipids and inflammatory mediators. This was a double-blind, randomised, controlled trial with two parallel groups. For 14 weeks, one group consumed 6 x 1 g capsules/d of monounsaturated oil (placebo group, PB), and the other group consumed 6 x 1 g capsules/d of LCn-3PUFA (fish oil group, FO), each comprising 70 mg EPA and 270 mg DHA. Both groups were on VLED for 4 weeks (n 14 PB, n 18 FO), which was then followed by 10 weeks of weight maintenance (n 12 PB, n 17 FO). Fasting blood samples, anthropometric measurements and 3 d food diaries were collected at baseline, at 4 and 14 weeks. A greater-than-2-fold increase occurred in plasma levels of EPA and DHA in the FO group (P<0.001). At 4 weeks, the mean weight loss was 6.54 (SD 2.08) kg (-6.9%) for PB and -6.87 (SD 1.83) kg (-7.7%) for FO. At week 14, after the maintenance phase, there was a further mean decrease in weight, -1.57 (SD 3.7) kg (1.85%) for PB and -1.69 (SD 2.32) kg (-1.9%) for FO. Both groups experienced improved metabolic profiles and there was a significant reduction in fat mass for the FO group at week 14 but not for PB. However, it would appear that supplementation with LCn-3PUFA had no significant effect on weight loss or weight maintenance over the 14 weeks.