Original Article
International Journal of Obesity (2007) 31, 1560–1566; doi:10.1038/sj.ijo.0803643; published online 15 May 2007
Randomized trial of weight-loss-diets for young adults varying in fish and fish oil content
I Thorsdottir1, H Tomasson2, I Gunnarsdottir1, E Gisladottir1, M Kiely3, M D Parra4, N M Bandarra5, G Schaafsma6 and J A Martinéz4
- 1Unit for Nutrition Research, Department of Food Science and Human Nutrition, Landspitali University Hospital, University of Iceland, Reykjavik, Iceland
- 2Faculty of Economics and Business Administration, University of Iceland, Iceland
- 3Department of Food and Nutritional Sciences, University College Cork, Cork, Ireland
- 4The Department of Physiology and Nutrition, University of Navarra, Navarra, Spain
- 5The Nutrition Laboratory, The National Research Institute on Agriculture and Fisheries Research, Lisbon, Portugal
- 6TNO Nutrition and Food Research, The Netherlands and Wageningen University, Wageningen, The Netherlands
Correspondence: Professor I Thorsdottir, Unit for Nutrition Research, Landspitali University Hospital, Eiriksgata-29, 101 Reykjavik, Iceland. E-mail: ingathor@landspitali.is
Received 2 August 2006; Revised 21 February 2007; Accepted 8 March 2007; Published online 15 May 2007.
Abstract
Objective:
To investigate the effect of including seafood and fish oils, as part of an energy-restricted diet, on weight loss in young overweight adults.
Design:
Randomized controlled trial of energy-restricted diet varying in fish and fish oil content was followed for 8 weeks. Subjects were randomized to one of four groups: (1) control (sunflower oil capsules, no seafood); (2) lean fish (3 
150 g portions of cod/week); (3) fatty fish (3 150 g portions of salmon/week); (4) fish oil (DHA/EPA capsules, no seafood). The macronutrient composition of the diets was similar between the groups and the capsule groups, were single-blinded.
Subjects:
A total of 324 men and women aged 20–40 years, BMI 27.5–32.5 kg/m2 from Iceland, Spain and Ireland.
Measurements:
Anthropometric data were collected at baseline, midpoint and endpoint. Confounding factors were accounted for, with linear models, for repeated measures with two-way interactions. The most important interactions for weight loss were (diet energy intake), (gender diet) and (gender initial-weight).
Results:
An average man in the study (95 kg at baseline receiving 1600 kcal/day) was estimated to lose 3.55 kg (95% CI, 3.14–3.97) (1); 4.35 kg (95% CI, 3.94–4.75) (2); 4.50 kg (95% CI, 4.13–4.87) (3) and 4.96 kg (95% CI, 4.53–5.40) on diet (4) in 4 weeks, from baseline to midpoint. The weight-loss from midpoint to endpoint was 0.45 (0.41–0.49) times the observed weight loss from baseline to midpoint. The diets did not differ in their effect on weight loss in women. Changes in measures of body composition were in line with changes in body weight.
Conclusion:
In young, overweight men, the inclusion of either lean or fatty fish, or fish oil as part of an energy-restricted diet resulted in 
1 kg more weight loss after 4 weeks, than did a similar diet without seafood or supplement of marine origin. The addition of seafood to a nutritionally balanced energy-restricted diet may boost weight loss.
Keywords:
fish proteins, n-3 fatty acids, weight-loss-diet, overweight, humans
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