The treatment of the
metabolic syndrome aims to improve
insulin sensitivity and correct/prevent the associated metabolic and
cardiovascular abnormalities. Since many individuals with the
metabolic syndrome are
overweight, dietary treatment should be primarily focused on
weight reduction. This approach can improve
insulin sensitivity and exert beneficial effects on all the other abnormalities clustering in the syndrome.
Insulin sensitivity can also be influenced by diet composition. In this respect, the specific effects of the quality of
dietary fat are of great interest, given the considerable evidence in experimental animals that saturated fat in the diet may lead to
insulin resistance. In man, there is indirect evidence that a higher saturated fat intake is associated with impaired
insulin action. Human studies have also attempted to evaluate the relationship between total fat intake and
insulin sensitivity. They are consistent in showing that fat intake is correlated with both plasma
insulin values (positively) and
insulin sensitivity (negatively). However, these correlations are largely mediated by
body weight. Conversely, intervention studies are consistent in showing that when total fat intake is moderately increased (from 20 to 40%), no major effect is observed on
insulin sensitivity. We have recently undertaken a large, multicentre intervention study in 162 healthy individuals given either a high-saturated-fat or a high-monounsaturated-fat diet for 3 months. It shows that a high-monounsaturated-fat diet significantly improves
insulin sensitivity compared to a high-saturated-fat diet. However, this beneficial effect of monounsaturated fat disappears when total fat intake exceeds 38% of total energy. Independently of its effects on
insulin sensitivity, diet composition can influence the factors clustering in the
metabolic syndrome.
Dietary carbohydrate increases
blood glucose levels, particularly in the postprandial period, and consequently also
insulin levels and plasma
triglycerides. The detrimental effects of a high-
carbohydrate diet on plasma
glucose/
insulin,
triglyceride/HDL or fibrinolysis occur only when
carbohydrate foods with a high glycaemic index are consumed, while they are abolished if the diet is based largely on fibre-rich, low-glycaemic-index foods. In conclusion,
weight reduction is a powerful measure for the treatment of
metabolic syndrome. Moreover, the diet for the treatment of the
metabolic syndrome should be limited in the intake of saturated fat, while high fibre/low-glycaemic-index foods should be used without specific limitations. Moderate amounts of monounsaturated fat could be permitted as they do not induce detrimental metabolic effects.