If you’re already skinny and lean, you can’t build muscle well unless you eat more.

When obese women eat extremely few calories (under 800 per day), they sometimes gain belly fat, lose muscle, and don’t lose much fat—making it worse than eating a little less.

Women and men gain muscle at about the same rate relative to how much muscle they started with, but women end up gaining less total muscle because they usually start with less muscle to begin with.