Expert: Ryan Hale - 4/6/2011

Question
I've heard repeatedly that if you don't consume enough calories you will go into "survival mode" and stop losing weight.  How can that possibly be true, when I have seen for myself people that are anorexic? If they stop eating enough they should go into survival mode and stop losing weight right?  But that isn't what happens, they do in fact keep getting thinner and thinner. So if I am overweight and stop eating, won't I in fact lose weight, just like a thin person who is anorexic?  Burning more calories than you take in is the key to losing weight so I do not understand why "experts" say if you don't eat enough you won't lose weight.  If I don't eat, biologically wouldn't I HAVE to lose weight?

Answer
Diana- survival mode doesn't mean not losing weight, it simply means that your metabolism will slow down and be altered, perhaps for a long time or the rest of your life.  That means the weight loss will slow down to a point where it seems like it has stopped, but you can't waste away to nothing.  Eventually people die of organ failure, usually the heart.  This happens around a point where weight loss slows almost to a stop.  It comes to almost a stop because the body is trying to stay alive to the point that your metabolic rate is barely above comatose level and your body starts to burn tissues that can supply a little energy but not result in a great deal of weight loss.

Another effect is that the movement of food through the digestive track will slow way down... that's part of the survival mode as well.  It is also the cause for much discomfort when people start to re-feed.  Often the person will drop out of treatment because of how they feel...that's where the bloating comes from because the food just sits in the GI tract.  Calorie balance is the ultimate deciding factor in weight loss, but your body is going to do all it can to maintain life, burn as little calories as possible, and use such little body tissue to do it that it seems like weight loss has stopped.