Issue 99 Item 6 Substituting Dietary Saturated Fat with Polyunsaturated Fat Chan

Dietary change can result in improved insulin sensitivity and less abdominal fat British dietary recommendations are to decrease total fat intake to less than 30 % of daily energy intake and saturated fat to less than 10 %. In practice, it is difficult for people to make these changes. It may be easier to encourage people to switch from a diet rich in saturated fatty acids to one rich in polyunsaturated fatty acids.

For the study a total of 17 subjects – six people with Type 2 (non-insulin-dependent) diabetes, six non-obese and five obese people without diabetes – were randomized to spend two 5-week periods on a diet rich in saturated or in polyunsaturated fatty acids, in a crossover design. At the start of the study and after each dietary period, we assessed abdominal fat distribution using magnetic resonance imaging, insulin sensitivity using hyperinsulinemic-euglycemic clamps and fasting lipid parameters.

The results showed that dietary compliance, assessed by weekly 3-day dietary records and measurement of biochemical markers, was good. Energy and fat intake appeared to be reduced on the diet rich in polyunsaturated fatty acids although body weights did not change. Insulin sensitivity and plasma low density lipoprotein cholesterol concentrations improved with the diet rich in polyunsaturated fatty acids compared with the diet rich in saturated fatty acids. There was also a decrease in abdominal subcutaneous fat area.

The researchers concluded that if the result is confirmed in longer-term studies, this dietary manipulation would be more readily achieved by the general population than the current recommendations and could result in considerable improvement in insulin sensitivity, reducing the risk of developing Type 2 diabetes. Diabetologia (2002) 45: 369-377