Diets high in monounsaturated fatty acids (MUFA) such as a Mediterranean diet may reduce the risk of cardiovascular diseases by improving insulin sensitivity and serum lipids. Besides being high in MUFA, a Mediterranean diet also contains abundant plant foods, moderate wine and low amounts of meat and dairy products, which may also play a role. We compared the effects of a high MUFA-diet with a diet high in saturated fatty acids (SFA) and the additional effect of a Mediterranean diet on insulin sensitivity and serum lipids.

A randomized parallel controlled-feeding trial was performed, in 60 non-diabetics (40–65y) with mild abdominal obesity. After a two week run-in diet high in SFA (19 energy-%), subjects were allocated to a high MUFA-diet (20 energy-%), a Mediterranean diet (MUFA 21 energy-%), or the high SFA-diet, for eight weeks. The high MUFA and the Mediterranean diet did not affect fasting insulin concentrations. The high MUFA-diet reduced total cholesterol (−0.41mmol/L, 95% CI −0.74, −0.09) and LDL-cholesterol (−0.38mmol/L, 95% CI −0.65, −0.11) compared with the high SFA-diet, but not triglyceride concentrations. The Mediterranean diet increased HDL-cholesterol concentrations (+0.09mmol/L, 95% CI 0.0, 0.18) and reduced the ratio of total cholesterol/HDL-cholesterol (−0.39, 95% CI −0.62, −0.16) compared with the high MUFA-diet.

Replacing a high SFA-diet with a high MUFA or a Mediterranean diet did not affect insulin sensitivity, but improved serum lipids. The Mediterranean diet was most effective, it reduced total and LDL-cholesterol, and also increased HDL-cholesterol and reduced total cholesterol/HDL-cholesterol ratio.