Many diets on the market rely on the concept of starving the body of calories so that it will burn stored energy. On the surface this makes sense. If you eat less calories than you burn, you will lose weight because the body will be burning stored fat for energy. Then when you scratch the surface you find a complex web of science and evolution that complicates the matter. Now a simple formula, less calories=weight loss, becomes a problem with many variables.
Let’s take a look at the science that makes starvation diets ineffective. The body is a complex machine that has one main purpose, survival. The body adjusts its responses and internal functions to maintain homeostasis. When a change occurs the body will fight against it to return to a state or normalcy. This is what happens when a person chooses a calorie-restriction diet.
The body is used to getting a certain number of calories per day (some even say per meal.) When that level changes the body changes its response. It begins to burn fewer calories to maintain its lean tissue and energy stores. So, the lower calorie diet only results in weight loss for a short time, until the body regulates its internal functions. Then the metabolism will be slower, so the body will burn fewer calories at rest. Each day the body will be burning fewer calories during the day. This means that the lower caloric intake will not result in further weight loss. And, even worse, when the normal caloric intake returns the body will be burning calories at the new, lower level which will result in the extra calories being stored as body fat. So, instead of losing weight, in the long run weight, more specifically fat, will be gained. Not a very successful weight loss plan.
It may be easier to understand in numbers. If a person normally takes in 2500 calories per day their metabolism will be set to burn 2500 calories each day. This means that taking in more than 2500 calories will result in weight gain and less will mean weight loss (at least for a short time.) Now, that person decides to go on a calorie-restriction diet and drops their calories to 2000 per day. That is a reduction of 500 calories a day, or 3500 calories per week. The first week this person will lose a pound, then the second week they may lose another pound and the third week will see about a half pound lost. By the end of the third week the metabolism will be reset for the lower calorie level, so weight loss will stop. After a frustrating couple of weeks of no weight loss, this person may give up on the diet and go back to normal eating. This new influx of 500 extra calories per day will result in a regaining of one pound per week for at least the firs three weeks. So, this person will have a net result of no weight loss or possibly gaining an extra half pound.
So, when seeking long-term, effective weight loss starvation, or calorie-restriction, diets are not the answer. They only result in the body seeking to survive by lowering the metabolism to match the new lower calorie level.