I think on survivor to some extent, and in WWII, when you are not eating much of anything at all - your body burns muscle and fat - whatever it can to survive, and the metabolism and energy and everything gets slow. Probably even bone density is used and the bones become brittle, so maybe even "weight" is lost from bone and just all over the body as muscle and fat, and organ tissue - whatever the body needs to use to create glucose as energy for the brain. This is an extreme example of "weight loss". (Well, bone wouldn't be used for energy, but without proper food, bone would be sacrificed for the body's calcium needs, and bone would just be broken down and not build back up)
Why someone who would eat less, would gain weight? Not sure about that? I think it's a very personal thing. Just depends on alot of things.
I have read if you eat small regular meals (healthier choices) throughout the day, you body burns energy evenly with maybe less going to fat stores.
But if you skip meals, go hungry for long periods of time (all day with no lunch) - things like that, you are signaling to your body that next time there is food it will need to save as much as possible to go through the next stretch of time where you do not eat for hours. So then for dinner, you may even eat a little more because you had deprived yourself all day and are hungrier, but also your body stores what it can to last the next day (as body fat or glycogen in the muscle). So if you are not really eating a whole lot overall (you have skipped meals) then I could see where the metabolism may slow some and the body try to store all it can to hold on to the energy it is given as fat stores when you do eat. Probably would make weight loss more difficult. I don't know for certain, but maybe eating this way the body might not really be able to build muscle properly? so the energy just goes to the fat stores and preserving the fat.
Also, if you just eat excess calories than you need (me and my sweet tooth, haha) :) then your body has no need for their use so they are stored as fat. But, you weren't asking about that - if you eat more than you need, then you will gain. Everybody gets that. :)
<message edited by Andelyn on Sunday, September 21, 2008 4:33 PM>