Dietary saturate/unsaturate ratio as a determinant of adiposity

The characteristic leanness of vegans and adherents to "Mediterranean" diet patterns may reflect the fact that the high saturate-to-unsaturate ratio of Western omnivore diets tends to impair muscle insulin sensitivity, leading to a compensatory up-regulation of insulin secretion. Since insulin signals adipocytes to take up and retain fatty acids, a high dietary saturate-to-unsaturate ratio would be expected to promote obesity. It is proposed that, at any given level of total fat intake, the dietary saturate/unsaturate ratio will correlate positively with BMI and propensity for weight gain - a readily testable prediction. The relatively low ratios of saturates to unsaturates and of essential to non-essential amino acids in plant-based diets may be primarily responsible for the low rates of obesity, diabetes, coronary disease, and "Western" cancers observed in quasi-vegan societies.