, Volume 51, Issue 7, pp 1261-1268

First online:

Beneficial effects of long-chain n-3 fatty acids included in an energy-restricted diet on insulin resistance in overweight and obese European young adults

  • A. RamelAffiliated withUnit for Nutrition Research, Landspitali-University Hospital & Faculty of Food Science and Nutrition
  • , A. MartinézAffiliated withDepartment of Physiology and Nutrition, University of Navarra
  • , M. KielyAffiliated withDepartment of Food and Nutritional Sciences, University College Cork
  • , G. MoraisAffiliated withDepartment of Biochemistry, Faculty of Medical Sciences, New University of Lisbon
  • , N. M. BandarraAffiliated withThe National Research Institute on Agriculture and Fisheries Research
  • , I. ThorsdottirAffiliated withUnit for Nutrition Research, Landspitali-University Hospital & Faculty of Food Science and Nutrition Email author 



Epidemiological research indicates that long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) improve insulin resistance. The aim of this study was to investigate the effects of seafood consumption on insulin resistance in overweight participants during energy restriction.


In this 8 week dietary intervention, 324 participants (20–40 years, BMI 27.5–32.5 kg/m2, from Iceland, Spain and Ireland) were randomised by computer to one of four energy-restricted diets (−30E%) of identical macronutrient composition but different LC n-3 PUFA content: control (n = 80; no seafood; single-blinded); lean fish (n = 80; 150 g cod, three times/week); fatty fish (n = 84; 150 g salmon, three times/week); (4) fish oil (n = 80; daily docosahexaenoic/eicosapentaenoic acid capsules, no other seafood; single-blinded). Fasting glucose, insulin, adiponectin, plasma triacylglycerol and fatty acids in erythrocyte membrane were measured at baseline and endpoint. Insulin resistance was calculated using the homeostasis model assessment of insulin resistance (HOMA-IR). Linear models with fixed effects and covariates were used to investigate the effects of seafood consumption on fasting insulin and HOMA-IR at endpoint in comparison with the control group.


Of the participants, 278 (86%) completed the intervention. Fish oil intake was a significant predictor of fasting insulin and insulin resistance after 8 weeks, and this finding remained significant even after including weight loss, triacylglycerol reduction, increased LC n-3 PUFA in membranes or adiponectin changes as covariates in the statistical analysis. Weight loss was also a significant predictor of improvements.


LC n-3 PUFA consumption during energy reduction exerts positive effects on insulin resistance in young overweight individuals, independently from changes in body weight, triacylglycerol, erythrocyte membrane or adiponectin.

Trial registration: NCT00315770.

Funding: The YOUNG study is part of the SEAFOODplus Integrated Project, which is funded by the EC through the 6th Framework Programme Contract No. FOOD-CT-2004-506359.


Glucose Insulin Insulin resistance LC n-3 fatty acids Weight loss