By: Thomas Pickering, MD, DPhil, FRCP, Director of Integrative and Behavioral Cardiology Program
of the Cardiovascular Institute at Mount Sinai School of Medicine, New York.

In many people hypertension occurs in conjunction with a combination of problems commonly referred as the “insulin resistance syndrome” (or sometimes as “syndrome X”). This includes (in addition to the high blood pressure), central obesity, insulin resistance (which can lead to diabetes), high cholesterol, and high triglycerides. An Australian study (whose results we have reported elsewhere) has shown that a diet that combines weight loss and a daily meal of fish produces a substantial reduction of blood pressure. In this report we describe the effects of the diet on blood lipids and glucose metabolism.

Sixty-three overweight men and women with hypertension were allocated to one of four treatment groups: weight loss, fish, weight loss plus fish, and no change. Those allocated to the two fish groups were advised to have one meal a day of fish, which consisted of frozen Greenland turbot, canned sardines, canned tuna, or canned salmon.

The average weight lost in the two weight-loss groups was 5.6 kilograms (12 pounds). Weight loss on its own resulted in an improvement in glucose and insulin metabolism (lower blood glucose and insulin), and an improvement in lipid metabolism (lower triglycerides and total cholesterol). Fish on its own did not have much effect on glucose metabolism but did lower triglycerides by 29%. However, the most striking benefits were seen in the group who were on the weight reducing and fish diets. Triglycerides fell by 38%, and HDL cholesterol increased by 24%. Glucose and insulin metabolism were also improved. None of the diets had much effect on total or LDL cholesterol.

Doctor’s comments

Central obesity (the “beer belly” type) is a major problem which leads to high blood pressure, high blood lipids, and diabetes, all of which act to increase the risk of heart disease. Conventional wisdom is to advise weight loss. What this study shows is that combining a daily meal of fish with the weight loss program has additional benefits, which should interact to lower the risk of heart disease. In another report of this study, the authors showed that the fish + weight loss diet lowered the blood pressure the most, and in this report they show that it also improves the lipids the most and reduces the chances of getting diabetes the most.

Where it was published

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