Dietary fat and insulin sensitivity in a triethnic population: the role of obesity. The Insulin Resistance Atherosclerosis Study (IRAS)
Published on Jan 1, 1997in The American Journal of Clinical Nutrition6.568
· DOI :10.1093/ajcn/65.1.79
From the Insulin Resistance Atherosclerosis Study (IRAS), 1173 men and women of African-American, non-Hispanic white, and Hispanic ethnicity with no history of diabetes were included in an evaluation of the cross-sectional relation of habitual dietary fat intake with insulin sensitivity (S I ) as assessed by minimal-model analysis of a 12-sample, insulin-modified frequently sampled intravenous-glucose-tolerance test. Dietary intake was measured by a food-frequency interview modified to enhance sensitivity to food choices within the three ethnic groups. Percentage of energy from total fat was associated with rank of S I (S I(rank) ; r = -0.06, P = 0.03), with log fasting insulin (r = 0.10, P < 0.001), and with BMI (r = 0.10, P < 0.001). Multiple-linear-regression models included S I(rank) as the dependent variable, dietary fat (g/d) as the primary independent variable adjusted sequentially for total energy, other covariates, body mass index, and waist-hip circumference ratio (WHR). For all subjects combined, total fat intake was inversely related to S I(rank) , but this association was not significant (P = 0.14) and was attenuated by adjustment for body mass index and WHR (P = 0.44). The association of total fat (g/d) with S I(rank) differed significantly (P < 0.01) for obese compared with nonobese individuals. Higher fat intake was associated with lower S I(rank) among obese (β = -1.40, P = 0.03) but not among nonobese persons (β = 0.16, P = 0.80). Among the obese (body mass index ≤ 63), adjustment for body mass index largely accounted for the observed association of dietary fat with S I(rank) . These findings were generally consistent for monounsaturated, polyunsaturated, and saturated fats. Among individuals already at increased risk for non-insulin-dependent diabetes mellitus because of obesity, high intake of dietary fat may worsen insulin sensitivity. This effect may be mediated by the relation of dietary fat to obesity.