Body fat is the ultimate survival insurance. Research by Leibel shows the body defends fat vigorously—increasing hunger, decreasing metabolism—because for most of human history, those who held onto fat survived famine and reproduced. Your body responds to weight loss as if starvation has begun. This defense mechanism doesn’t know about grocery stores or desk jobs. Understanding this isn’t fatalism; it’s knowing what you’re working with.
This companion covers evolutionary logic, what fat does, and working with biology. (4 min read)