Dietary fat and insulin sensitivity in a triethnic population: the role of obesity. The Insulin Resistance Atherosclerosis Study (IRAS)

Abstract

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 (SI) 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 SI (SI(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 SI(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 SI(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 SI(rank) differed significantly (P < 0.01) for obese compared with nonobese individuals. Higher fat intake was associated with lower SI(rank) among obese (beta = -1.40, P = 0.03) but not among nonobese persons (beta = 0.16, P = 0.80). Among the obese (body mass index < or = 63), adjustment for body mass index largely accounted for the observed association of dietary fat with SI(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.

Diet but not aerobic exercise training reduces skeletal muscle TNF-a in overweight humans

“…In particular, a higher ratio of carbohydrate to fat consumption has previously been associated with improved insulin sensitivity [24,25,26]. While fasting insulin levels in this study were reduced in conjunc- tion with the HOMA beta cell function index, the HOMA insulin resistance index just failed to reach statistical significance (p=0.08).…”

Serum phospholipid and cholesteryl ester fatty acids and estimated desaturase activities are related to overweight and cardiovascular risk factors in adolescents

“…14,15,45 In summary, this study shows that adverse patterns of fatty acids and DA are already associated with overweight and insulin resistance before adulthood. Results of observational and clinical studies conducted in humans have shown that a diet high in total or saturated fat is associated with abnormal glucose concentrations 3,46,47 or insulin resistance, 3,48 whereas diets enriched in monounsaturated fat 39,49 or Serum fatty acids and CVD risk factors in overweight adolescents LM Steffen et al linoleic acid 50 improve insulin sensitivity. Beneficial changes in the CE fatty acid profile and DA ratios were related to improved insulin sensitivity in a population at risk for type 2 diabetes.…”

Nut consumption, body weight and insulin resistance

“…High-fat diets have been associated with a detrimental effect on glucose homeostasis in epidemiological and intervention studies (Mayer-Davis et al, 1997). There is little evidence on the role of nuts, but it seems that, despite being rich in fat, they do not negatively affect glucose homeostasis.…”