jojo, the body is continually breaking down muscle cells and using them as nutrients. If you could get it to stop doing so, you might very well put on 100 ibs of muscle in a year without working out. Needless to say, the lower your caloric intake and the farther apart your meals, the greater its tendancy to do so.
Griz, no your summary explains it rather well. The human body has evolved for maximum energy conservation. Given ANY indication that its energy supply (food) might be becoming less plentiful (going any peroid of time without eating... meaning, in our natural environmental conditions, that you do not have access to food for hours becuase you couldn't find any) will cause it to hoard as much body fat as possible to prevent starvation. If you are continually eating smaller meals, it signals to your body that there is a continual supply of food available, and little need to hold on to the fatty acids bound in our adipose tissue.
Meal frequincy also has alot to do with insulin levels. Obviously all foods (except pure fat like olive oil or lard) cause some insulin response, however it is in proportion to the amount eaten. If you take a given amount of food, and break it into meals, obvioulsy the more meals it is divided into, the higher one's insulin levels rise. By breaking it down into many meals, one's insulin levels will always be lower. Insulin is the primary fat storage hormone in the body. While you must have some in order for survival, really, if insulin levels are kept below a certain level, it is impossible to gain any signifigant amount of body fat, even when eating excess calories. The same holds true for fat loss. The higher's one's insulin levels rise, the more difficult it is to use the fatty acids present in yoru fat cells for fuel. It will slow down their release into the bloodstream.
There is also the factor of the boost in metabolism followed by a meal. Every time you eat, you get a small boost in your metabolic rate, and the mere act of digestion used calories. Woul you rather get that small metabolic boost 3 times a day, or 12? Granted the difference might only be an extra 100 calories a day burned in some individuals, however, that adds up over the course of a several month long diet. It could equal another ibs of body fat lost every month.