Diet and exercise as regulators of lipid risk factors.

Comparisons of different countries have shown that populations with a low dietary intake of saturated fat also have a low mortality from coronary heart disease. Controlled-feeding experiments have shown that the potential for altering plasma cholesterol levels and, consequently, altering the risk of coronary heart disease by dietary modification is great. However, in practice the influence of dietary advice to the general population on plasma cholesterol levels has been less pronounced. Several investigators have shown that by decreasing the intake of saturated fats and dietary cholesterol and increasing the intake of polyunsaturated fats and foods providing soluble fibre, plasma cholesterol levels can be reduced by up to 29% and low density lipoprotein (LDL)-cholesterol by over 33%. In most studies, levels of high density lipoprotein (HDL)-cholesterol are not materially altered by modern lipid-lowering diets; generally, plasma levels are maintained, or increased after correction of overweight is is achieved. It has been calculated that the risk of fatal coronary heart disease is 32% lower in subjects consuming such a diet than in those following a typical American diet, and life expectancy is 5 years greater in the former group. Life expectancy is also 2 to 3 years longer in populations habitually following low fat diets than in Western populations. Frequent exercise has been inversely related to risk of coronary heart disease. Physically active individuals have a more favourable lipoprotein profile than sedentary individuals but the extent of a direct effect of exercise on lipoprotein levels is not known.