Trans Fats Consumption and Body Mass Index in Cross Sectional Analysis

Background Trans fats remain on the market in parts of the world. Emerging evidence suggests that factors beyond calorie balance may affect fat deposition and body mass index ( BMI ). Trans fats are prooxidant, proinflammatory, and have shown adverse metabolic effects and increased fat deposition in animals. Objective To assess the relation of dietary trans fatty acid consumption ( dTFA ) to BMI in humans. Design Cross-sectional analysis of baseline data from a broadly-sampling study. Setting Community-dwelling adults from Southern California. Participants 1018 adult men and women aged 20-85 without known diabetes, CVD, or cancer, with screening LDL 115-190mg/dL. Women of procreative potential and children were excluded. Measurements Height, weight, and waist circumference were measured, and BMI calculated (kg/m 2 ). The Fred Hutchinson Food Frequency Questionnaire provided data on dTFA (grams/day) and calories consumed. Additional covariates included activity, chocolate consumption frequency, and mood. Regression assessed the relation of BMI (outcome) to dTFA, unadjusted and in models adjusting for age and sex, and adding calories and activity, chocolate consumption frequency, and mood. Results Higher dTFA was associated with higher BMI and waist circumference. The coefficient was strengthened, not attenuated, with adjustment for calories and activity, and other assessed covariates. In the fully adjusted model, each gram/day of dTFAs was associated with 0.44 higher BMI (SE=0.12;95%CI=0.21,0.67); P<0.001 and 1cm greater waist circumference (SE=0.35;95%CI=0.37,1.7); P=0.003. Conclusion Findings: relating greater dTFA to higher BMI in humans comport with experimental data in animals, extend adverse metabolic associations of dTFA, and buttress evidence that foods’ composition, as well as caloric number, bears on BMI. Findings are cross-sectional but strength and consistency of association, biological gradient, and biological plausibility add “weight” to the prospect of a causal connection. Strengths and limitations of this study Findings: are cross-sectional and rely on dietary recall. Observational studies carry risks of bias and confounding; but randomized trials are problematic where products with potential for harm are under evaluation. Although some nations have implemented plans to remove or reduce dTFAs from the food supply, dTFA remain on the market in other nations, rendering findings of continued interest. The association of increased dTFA with increased BMI and waist circumference fits with other documented adverse metabolic associations of dTFA and is buttressed by experimental documentation that dTFA (without excess calories) increases visceral fat in animals, supporting prospects for causality in the observed association.