Abstract MP050: Changes in Dietary Fat Intake and Long-term Weight Change in US Women and Men

Introduction: The role of dietary fat intake in body weight regulation remains controversial and few studies have examined long-term changes in types of dietary fat and weight change in longitudinal studies. Methods: We examined the association between changes in energy from dietary fat and weight change in three large, prospective cohorts including 102, 123 U.S. women and men who were free of diabetes, cardiovascular disease and cancer at baseline. Linear mixed model was used to assess the association between changes in energy from specific dietary fat and weight changes at 4-year intervals with multivariable adjustment for age, baseline body-mass index at each period, and simultaneous changes in dietary factors (total energy, energy from protein, cereal fiber) and lifestyle factors (smoking, physical activity, television watching, sleep duration). Results: Increased intake of polyunsaturated fatty acid (PUFA) was inversely associated with weight gain. A 5% increment in energy from total PUFA was associated with less weight gain (-1.8 lb, 95% CI: -1.95 to -1.65, p<0.0001) and a 5% increment in energy from n-6 PUFA was associated with 0.90 lb (95% CI: -1.07 to -0.73, p <0.0001) less weight gain over 4-yr period. For marine n-3 PUFA, a 0.3% increase in intake was associated with 2.28 lb (95% CI: -2.50 to -2.10, p<0.0001) less weight gain; a 0.3% increase in intake of vegetable n-3 PUFA (ALA) was also associated with less weight gain (-0.77 lb, 95% CI: -0.86 to -0.68, p<0.0001) at a 4-year interval. The effect of monounsaturated fatty acid (MUFA) intake on weight changes varied across time as the major food contributors to MUFA shifted from animal sources since 1986 to plant sources after 1994 in these cohorts. Prior to 1994, increasing intake of MUFA was positively associated with weight gain (0.50 lb, 95% CI: 0.36 to 0.65), whereas after 1994, increasing intake of MUFA was inversely associated with weight gain (-0.56 lb, 95% CI: -0.56 to 0.07, p<0.0001 for interaction). In addition, a 5% increase in energy from SFA was associated with 1.71 lb (95% CI: 1.59 to 1.83) greater weight and a 1% increase in energy from trans -fat was associated with 1.97 lb (95% CI: 1.86 to 2.08) greater weight gain within each 4-year period. Conclusion: Different types of dietary fats have divergent associations with long-term weight change: higher intakes of PUFA (both n-6 and n-3 PUFA) and plant-based MUFA were associated with less weight gain, whereas increasing saturated and trans -fat intakes were associated with greater weight gain. Our results support the current dietary guidelines that recommend unsaturated fats as replacements for saturated and trans -fats.