I don't think this is right -- my understanding is the fat tissue closely correlates with fat in the diet. E.g., "Tissue and blood fatty acids, because they a

I don't think this is right -- my understanding is the fat tissue closely correlates with fat in the diet. E.g., "Tissue and blood fatty acids, because they are mainly derived from the diet, have been used as biomarkers of dietary intake for a number of years." from "Fatty acid composition of adipose tissue and blood in humans and its use as a biomarker of dietary intake" https://www.sciencedirect.com/science/article/abs/pii/S0163782708000283?via%3Dihub https://www.sciencedirect.com/science/article/abs/pii/S01637... Of course, lipogenesis is a thing, but it only produces SFA or MFA -- not PUFA. I can't find a reference, but if I'm not mistaken obese people have a higher percentage of body fat as PUFA than non-obese people, which, if true, is another way we can tell a significant portion of their fat must be coming from the diet. I guess it might be possible to eat sufficient quantities of high-carb, very-low-fat diet to drive enough lipogenesis to get fat, though I don't know if this actually happens in practice. As one sort of silly example, people eating a pure potato diet lose weight easily, with no restriction on total calories.