The ratio of ω6 to 3 polyunsaturated fatty acid (PUFA) in western diet has remarkably increased over the past decades. This change in dietary fatty acid (FA) composition, independent of the total caloric intake and total fat intake, may contribute to the obesity epidemic in many populations. Experimental studies show that 3 and ω6 FAs play different role in adipogenesis, lipid homeostasis, brain-gut-adipose axis signaling, and systemic inflammation, resulting in divergent effects on body fat

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... rowth. Evidence from human studies remains limited and inconclusive. Very few observational studies and clinical trials have examined the association between composition of PUFA, particularly 6 FA and ω6/3 ratio, with obesity-specific parameters. A consensus on the optimal intake of 3 and ω6 subtype FAs and ω6/3 ratio in diet is lacking. We reviewed the temporal change in dietary PUFA composition in US, experimental studies that examine the effects of ɷ3 and ω6 FAs on body fat, and epidemiologic studies that assess the association between dietary PUFAs and the development of obesity. Future studies need to further evaluate dietary FAs and their biomarkers in association with objective and longitudinal measurements of body fat and elucidate the potential role of diet with a balanced 3 and ω6 FA composition in the primary prevention of obesity.