Background/Objective:Previous research has focused on associations between dietary fat and body mass index (BMI), but the contributions of different types of fat to BMI remain unclear. The purpose of this study is to estimate whether plasma phospholipid omega-3 (n'3), omega-6 (n'6) or trans fatty acids are associated with BMI at baseline and with subsequent BMI changes over time; and whether total phospholipid n'6 or trans fatty acids modify any association between phospholipid n'3 and BMI.Methods:Cross-sectional and longitudinal linear mixed models include 6243 participants in the Multi-Ethnic Study of Atherosclerosis (MESA) cohort. Participants were 45'84 years old, had no history of cardiovascular disease at baseline (2000'2002) and were followed for up to 10 years. Plasma phospholipid fatty acids were measured using fasting plasma samples at baseline. Fully adjusted models include demographics, health behaviors and other fatty acids (n'3, n'6 and trans) as appropriate.Results:In fully adjusted models, phospholipid n'3 fatty acid levels were inversely associated with baseline BMI (P trend <0.001). Baseline BMI was 1.14 (95% confidence interval (CI): 0.71, 1.57) kg m -2 lower among participants with total n'3 values in the highest vs the lowest quartiles, but was not associated with changes in BMI. Total phospholipid n'6 was positively associated with baseline BMI in partially adjusted but not fully adjusted models. No overall association was observed between fatty acid levels and changes in BMI. No clear association was observed between trans fatty acids and baseline BMI or BMI change. No effect modification in the association between phospholipid n'3 and baseline BMI or BMI change was observed by either phospholipid n'6 or trans fatty acids.Conclusions:Phospholipid total and specific n'3 fatty acid levels were inversely associated with BMI at baseline, whereas associations tended to be positive for total n'6 fatty acids. Significant associations between fatty acid levels and BMI changes were not observed.
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