Why do people always say that if you don't eat, your body will go into starvation mode and store fat, so you wont lose any fat, but gain more when you start eating again? Is it an urban myth? I went through a stressful time a few years back and couldn't eat for a couple of weeks. I lost loads of weight. More than a stone I think.
Surely anorexics are losing fat? And Christian Bale stopped eating to lose weight for The Machinist. I don't see him wobbling round his latest movies.
Yes, in "starvation mode" fat is NOT stored, it is used up and goes through a chemical cycle which is very inefficient for producing energy. I this process continues then a state of ketoacidosis is produced which is life threatening.
It's not magic, extreme conditions will still starve you. Fail to eat at all and you will still waste away to nothing. But there is still an ability of the body that kicks in to try to get over lean times. It conserves whatever it can to minimise potential future problems, and if you start eating again it'll take a while to revert back to normal.
With a sudden reduction in diet the body has the ability to lower it's metabolic rate and use what it is getting more efficently. This is a survival strategy from when food was only available spasmodically ( feast or famine). One reason why crash diets are to be avoided