Omega-6 polyunsaturated fatty acids and adiposity in the UK Biobank Cohort: a cross-sectional and longitudinal...

The role of n-6 PUFA, especially linoleic acid (LA), in adiposity remains contested. While clinical interventions suggest improved body composition with higher LA intake, observational evidence using dietary data is inconsistent, and few studies consider circulating fatty acids or longitudinal changes in adiposity. Using multivariable linear models, we evaluated cross-sectional and longitudinal associations between n-6 PUFA and waist circumference (WC), weight and whole-body fat mass (FM) in the UK Biobank Cohort. Cross-sectionally (n 272 587, 54 % female, mean age 57 years), higher circulating LA was inversely associated with WC, weight and FM. Participants in the highest v. 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 n-6 were generally consistent with those for LA. Conversely, non-LA n-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 (n 58 335, 51 % female, mean age 55 years) largely corroborate these patterns, with annual changes in WC, weight and FM inversely associated with LA and positively associated with non-LA n-6. Higher circulating LA, but not non-LA n-6, was associated with lower WC, weight and FM both cross-sectionally and longitudinally. Our findings potentially support dietary recommendations to promote LA-rich oils. Divergent associations between LA and non-LA n-6 caution against treating n-6 PUFA as a homogeneous group. Examining the distinct health effects of individual non-LA n-6 is warranted.