@selzero Bouts with starvation permanently alter metabolism to make future obesity more likely when food becomes more available. There is a virus, SMAM-1, that makes chickens fatter as they starve. It is zoonotic to humans. This and select human adenoviruses affect body fat composition. It ain't just "choose to eat too many calories". It is also living constantly awash in cortisol from lack of care and institutional abuses.
Let us observe results when poors switch diet to eat the rich.