Circulating Fatty Acid Composition and Subsequent Adiposity Gain: A Prospective Study in the China Kadoorie Biobank

Background/Objectives: Evidence linking circulating fatty acids to adiposity gain remains limited. We examined associations of circulating fatty acid composition with longitudinal adiposity progression among Chinese adults. Methods: We included 1498 participants from the China Kadoorie Biobank with baseline nuclear magnetic resonance measurements of circulating fatty acid proportions and repeated measurements of body mass index (BMI) and waist circumference over a median of 8.22 years. Excessive adiposity increase was defined a priori as a BMI increase of ≥5% from baseline. Modified Poisson regression was used to estimate risk ratios (RRs) or prevalence ratios and their 95% confidence intervals (CIs) with multivariable adjustment when appropriate. Results: Overall, 499 participants (33.3%) experienced excessive adiposity increase. A one-standard-deviation (SD) higher monounsaturated fatty acid (MUFA) proportion was associated with a lower risk of excessive adiposity increase (RR = 0.870; 95% CI, 0.801–0.945; q = 0.004), whereas a higher ω-6 proportion was associated with a higher risk (RR = 1.115; 95% CI, 1.029–1.208; q = 0.016). However, in the cross-sectional analyses, MUFA and ω-6 showed associations with baseline overweight or obesity in directions opposite to their prospective associations with excessive adiposity increase. Conclusions: Higher circulating MUFA and ω-6 proportions were associated with lower and higher risks of a ≥5% BMI increase, respectively. The associations were less consistent across alternative outcome definitions, particularly for ω-6.