Dietary fat has been strongly implicated in Western cultures as a factor that contributes to high rates of heart disease. In a study published in the American Journal of Clinical Nutrition, Raeini-Sarjaz et al. investigated whether fat restriction differed from energy restriction in its effect on circulating concentrations of serum lipids. Overall, plasma lipid profiles differed after diets based on reductions in fat, energy or both. The authors conclude that the energy-restricted diet offered the most positive alteration of lipid profiles through favorable changes in HDL-cholesterol, triacylglycerol concentrations, and HDL:LDL ratios.
Eleven healthy nonobese men aged 40-60 years were studied at McGill University, Montreal. All had elevated LDL cholesterol and triacylglycerol levels and a family history of cardiovascular disease (CVD). In a crossover design, the men consumed 4 different diets for 4 weeks each: 1) a typical Western diet without fat or calorie restriction, 2) a low-fat diet with no restriction of calories, 3) a low-fat and calorie-restricted diet, and 4) a low-calorie diet with no fat restriction. Body weight decreased with all of the diets, and the greatest loss (3.6 kg average) resulted from 4), the low-calorie diet without fat restriction. The diets low in fat and low in both energy and fat resulted in similar reductions in LDL-cholesterol. However, the low-fat diet elevated triacylglycerols and suppressed HDL-cholesterol when compared to the other diets. Of all the diets, the energy-restricted diet had the most beneficial effects on serum lipids by lowering triacylglycerol concentrations and elevating HDL cholesterol more than the other diets, and by producing the greatest improvement in HDL:LDL ratios. The authors suggest that current recommendations calling for low-fat diets to reduce CVD risk should be reconsidered, with more focus being directed to reductions in energy intake for individuals with excess body weight.