Leptin, a circulating hormone secreted from adipocytes, is an index of adiposity and is reduced by caloric restriction and weight loss. A recent population study suggested that dietary-derived ω3 fatty acids lower leptin levels independent of body fat.
To examine whether dietary fish enhanced the effects of weight loss on serum leptin levels, in 69 overweight, treated hypertensive men and women.
Participants were randomized to a daily fish meal, a weight-reduction regimen, the two regimens combined or a control group for 16 weeks.
A total of 63 individuals completed the study. Weight fell 5.6 ± 0.8 kg with energy-restriction. Blood pressure (BP) reductions in the combined fish-weight loss group were twice that seen with either intervention alone. At baseline, in all groups combined, serum leptin levels correlated with serum insulin (r = 0.307, P = 0.014), but not with body weight. The greatest change in serum leptin occurred in the fish-weight loss group (control, 0.60 ± 0.76 ng/ml; fish, 1.20 ± 0.79 ng/ml; weight loss, −1.40 ± 1.05 ng/ml; fish-weight loss, −5.08 ± 1.64 ng/ml). In the fish-weight loss group, the change in serum leptin was predicted by changes in serum insulin (r = 0.488, P = 0.038), 24-h BP (systolic BP (SBP): r = 0.435, P = 0.060; diastolic BP (DBP): r = 0.563, P = 0.018) and 24-h heart rate (0.584, P = 0.028). Using general linear models, there was a significant fish x weight-loss interaction (P = 0.008) on post-intervention serum leptin after adjustment for baseline levels, independent of post-intervention insulin.
A daily fish meal as part of a weight-reducing regimen was more effective than either measure alone at reducing leptin levels. Reductions in leptin may be related to the substantial fall in BP seen with the fish-weight loss program.
aSchool of Medicine and Pharmacology, Royal Perth Hospital Unit, University of Western Australia and Western Australian Institute for Medical Research, Perth and bInternational Diabetes Institute, Melbourne, Australia.
Sponsorship: Supported by a Program Grant entitled ‘Studies in Hypertension and Cardiovascular Disease’ from the National Health and Medical Research Council of Australia. Fish was donated by Kailis & France Pty Ltd (Perth, Western Australia) and King Oscar Fine Foods Pty Ltd (Melbourne, Australia) subsidized the cost of canned sardines.
Correspondence and requests for reprints to Trevor A. Mori, School of Medicine and Pharmacology, Royal Perth Hospital Unit, The University of Western Australia, Medical Research Foundation Building, Box X 2213 GPO, Perth, Western Australia 6847. Tel: +61 8 9224 0273; fax: +61 8 9224 0246; e-mail: firstname.lastname@example.org.
Received 20 February 2004 Revised 10 May 2004 Accepted 8 June 2004