Insulin resistance as a modifier of the relationship between dietary fat intake and weight gain

To investigate whether insulin resistance modifies the rate of weight gain associated with a high percent of energy intake from dietary fat.

Longitudinal, observational population study.

A total of 782 nondiabetic Hispanic and non-Hispanic white free-living adult residents of the San Luis Valley in Colorado.

Subjects were seen up to three times over a 14-y period. Weight, height, fasting insulin and glucose, diet by 24 h recall, and self-reported physical activity were collected at each visit.

Percentage of energy intake from dietary fat was positively associated with weight gain over time (P=0.0103). High intake of dietary fat was more strongly related to weight gain in women than in men, and in those with lower total energy intake levels. The relationship between weight change and relative macronutrient intake also varied by baseline insulin sensitivity (P=0.0025). Weight gain over time in individuals with relative insulin resistance at baseline, as measured by QUICKI, was the greatest among those who consumed a higher percent of energy from fat.

Percentage of total intake from dietary fat predicts weight change independent of total energy intake. Nondiabetic, insulin-resistant individuals are particularly susceptible to the weight gain associated with high levels of dietary fat intake. Further investigation into the relationship between insulin resistance, diet, and weight gain is warranted.