Abstract
BACKGROUND: The role of omega-6 polyunsaturated fatty acids (PUFAs), especially linoleic acid (LA) in adiposity remains contested. While clinical interventions suggest improved body composition with higher LA intake, observational evidence is inconsistent, and few studies incorporate repeated measures to examine longitudinal change. OBJECTIVE: To investigate associations of circulating LA, non-LA omega-6, and total omega-6 PUFAs with adiposity outcomes in the UK Biobank. METHODS: Multivariable linear models evaluated cross-sectional and longitudinal associations between omega-6 fatty acid levels and waist circumference (WC), weight, and whole-body fat mass (FM) adjusting for relevant demographic, lifestyle and medical history covariates. Models considered FA levels per interquintile range and by quintiles. RESULTS: Cross-sectionally, higher circulating LA was inversely associated with WC, weight, and FM. Participants in the highest versus lowest quintile of LA had significantly smaller WC [-11.04 (-11.17, -10.91) cm], lower weight [-11.77 (-11.92, -11.62) kg], and lower FM [-7.87 (-7.97, -7.77) kg]. Associations for total omega-6 were generally consistent with those for LA. Conversely, non-LA omega-6 was positively associated with WC [1.46 (1.32, 1.61) cm], weight [2.41 (2.25, 2.58) kg], and FM [1.81 (1.69, 1.92) kg]. Longitudinal analyses largely corroborated these patterns, with annual changes in WC, weight, and FM inversely associated with LA and positively associated with non-LA omega-6. CONCLUSIONS: Higher circulating LA, but not non-LA omega-6, was associated with lower WC, weight, and FM both cross-sectionally and longitudinally. Our findings support dietary recommendations to promote LA-rich oils. Divergent associations between LA and non-LA omega-6 caution against treating omega-6 PUFAs as a homogenous group, and there remains a need to examine the distinct health effects of individual non-LA omega-6.