Dietary fish as a major component of a weight-loss diet: effect on serum lipids, glucose, and insulin metabolism in overweight hypertensive subjects

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Abstract
Background: Obesity in hypertensive patients is associated with dyslipidemia and insulin resistance, both of which are improved by weight control. n−3 Fatty acids have diverse effects on mechanisms underlying atherosclerosis, including a decrease in serum triacylglycerols and an increase in HDL2 cholesterol. Objective: The objective was to examine whether dietary fish enhances the effects of weight loss on serum lipids, glucose, and insulin in 69 overweight, treated hypertensive patients. Design: Overweight patients being treated for hypertension were randomly assigned to either a daily fish meal (3.65 g n−3 fatty acids), a weight-loss regimen, the 2 regimens combined, or a control group for 16 wk. Results: Sixty-three subjects completed the study. Weight decreased by a mean (±SEM) of 5.6 ± 0.8 kg with energy restriction. Weight loss decreased fasting insulin (P = 0.003) and the area under the curve for insulin (P = 0.003) and glucose (P = 0.047) during an oral-glucose-tolerance test. The greatest decrease occurred in the fish + weight-loss group. There was no independent effect of fish on glucose or insulin. Fish increased HDL2 cholesterol (P = 0.004) and decreased HDL3 cholesterol (P = 0.026) without altering total, LDL, or HDL cholesterol. Weight loss had no effect on these variables. Fasting triacylglycerols fell significantly with fish consumption (29%) and weight loss (26%). The fish + weight-loss group showed the greatest improvement in lipids: triacylglycerols decreased by 38% (P < 0.001) and HDL2 cholesterol increased by 24% (P = 0.04) compared with the control group. Conclusions: Incorporating a daily fish meal into a weight-loss regimen was more effective than either measure alone at improving glucose-insulin metabolism and dyslipidemia. Cardiovascular risk is likely to be substantially reduced in overweight hypertensive patients with a weight-loss program incorporating fish meals rich in n−3 fatty acids.