Is the association between dietary fat intake and insulin resistance modified by physical activity?

Abstract

The rising prevalence of type 2 diabetes, a condition associated with insulin resistance, is commonly attributed to changes in dietary patterns and physical activity levels in susceptible populations. However, few studies have described the independent effects of dietary intake and physical activity on the degree of insulin sensitivity within populations or examined the possibility of interactions between dietary factors and physical activity. This study was undertaken to describe the relationship between the quantity and pattern of dietary fat intake on fasting insulin levels (a marker of insulin sensitivity) and to investigate whether the association was modified by physical activity. A cross-sectional study of 815 nondiabetic men and women (30 to 71 years) recruited from a population-based sampling frame was undertaken. Diet was characterized using a semiquantitative food frequency questionnaire. Physical activity level (PAL), the ratio of total energy expenditure to basal metabolic rate, was estimated using individually calibrated heart rate monitoring, a method previously shown to be an objective and valid method for assessing total energy expenditure. In a linear regression model adjusted for total energy intake, total fat intake bordered on a significant association with fasting insulin (b = 0.000081; P =.058), and the polyunsaturated to saturated fat ratio (P:S ratio) of the diet was negatively associated with fasting insulin concentration (b = -0.37, P