Foods, nutrients or whole diets: effects of targeting fish and LCn3PUFA consumption in a 12mo weight loss trial

Overweight/obese Australian adults; mean age 45 ± 10 y; mean BMI 31.3 ± 3.5 kg/m2; 28% male; 118 participants randomized to three parallel arms in a 12-month randomized, placebo-controlled trial.

Control: olive oil placebo capsules 1 g/day for 12 months; Fish: olive oil placebo capsules 1 g/day for 12 months; Fish + S: LCn3PUFA (EPA 420 mg + DHA 210 mg) capsules daily for 12 months.

All groups lost weight over 12 months with no significant differences between arms. Weight changes: Control −4.5 kg, Fish −4.3 kg, Fish + S −3.3 kg (p<0.001 for time; no group differences). Percent body fat changes: −1.5%, −1.4%, −0.7% respectively (p<0.001; no group differences). LCn3PUFA status improved only in Fish + S (erythrocyte omega-3 index ~4.4% vs ~3.4% in Fish; p=0.007), but this did not translate into greater weight loss or major cardiovascular risk changes beyond those from weight loss. Conclusion: Advising two weekly fish meals did not enhance weight loss beyond a healthy low-calorie diet, and LCn3PUFA supplementation did not improve weight loss; larger studies may be needed to detect small effects.

Long-term free-living design with notable attrition; adherence to fish intake and to supplements varied; baseline LCn-3 intakes were modest, which may have limited observed effects; results may not generalize beyond overweight/obese Australian adults; study may have been underpowered to detect small between-group differences.