One of the key aspects that is often unheeded in dieting is the body’s ability to adapt to anything you do, and slowly reverse (or minimally, fight back hard) against any thing that happens to it that it sees as harmful. Calorie restriction is something the body sees as a stressor…It requires a certain amount of calories to function (which is in itself, variable) and when it does not receive its needed amount of calories, it responds in a few ways
#1 – Which is the one we want – it pulls energy from stored glycogen, body fat and muscle tissue (in that order usually)
#2 – Which we don’t really want – Is it down-regulates our metabolism. For each day the body doesn’t get as much calories as it thinks it needs, it makes chemical changes that signal the body to essentially use less.
#3 – Which we REALLY don’t want, is in the course of the chemical body changes, it decreases our testosterone production and increases our cortisol production. Which, essentially create a situation that the longer we diet (and the lower test levels, and higher cortisol levels go), the MORE likely we are to use that hard earned muscle for energy.
If this process of calorie restriction goes on long enough, it puts the body into a sort of starvation mode, which many contest dieters and other heavy dieters have experienced, where it seems no matter how little they eat, they cannot lose weight. The body essentially does this as a survival mechanism for what, it thinks, is impending death from starvation.
What’s important to understand about body chemical processes and hormones is, the longer they are suppressed (or incited) the longer it takes for them to rebound. This is what you often see in people (in women much more than men, due to lower overall food intake) who did extreme or contest diets for several months, and afterwards their weight increases to far more than it was at the start…..Chances are, they are eating far less than they were prior to dieting, however the body chemicals and hormones that signal the body what to do have been altered and their response to that food intake is completely different, and they just gain weight.
For this reason it’s very important to alternate your dieting with periods (not a day here and there) of much increased calorie intake. The goal for these times is to increase your calories significantly, while maintain the best shape you can. I am a big proponent of meal timing in this situation as it encourages the body to use more calories/energy when active and less when it is sedentary, which helps avoid fat storage.