The Science of Fasting

Energy balance (calories in, calories out) still matters relative to fat loss. Your alternate day fasting is just changing how you reduce your calories. If you overeat fat, as promoted by Fung and others with the therapeutic keto diet, you'll eventually stall out.

Lots of times, the yo yo dieting is due to your fat cells not actually leaving the body. They just shrink. And when you come out of a prolonged period of caloric deficit (ie weight loss diet), those fat cells are waiting for any extra calories you take in. So unless you're meticulous with tracking calories at maintenance as well as when dieting, you can see any increase in weight very quickly and easily.