Wednesday, March 26, 2008

The Metabolic Effects of Eating Less

Dieting affects your metabolic rate. If you start to eat less your body slows down the rate at which it functions.

It is only relatively recently that there have been ampleamounts of food available to most people in the western world. In terms of human existence on earth we are still programmed to deal with droughts, food shortages and periods of starvation. It is far more damaging and more likely in evolutionary terms for the body to starve to death than it is to overeat. And so we have evolved with the perfect method for avoiding starvation during a period of food shortage: storing excess food when it is available. This excess food is stored mainly in the form of fat, which is oxidised to produce energy when needed.

Diet Start

Metabolic rate refers to the amount of energy made available for use for a specific period of time. Our metabolic rates are also perfectly adapted for food shortages. If we decrease our food intake our bodies prepare themselves for the anticipated assault on stored food. The metabolic rate decreases so that the body can function as efficiently as possible and therefore use as little energy as possible and as little stored fat. Dieting for a period of fourteen days can lead to a decline of up to 20 per cent of the metabolic rate.

A recent study at the Rockefeller University in New York examined the effects of dieting on dieters' daily energy requirements. A group of obese people were studied; they had lost substantial amounts of weight and yet were still overweight by an average of 86 pounds. They found that as they lost weight their daily energy requirements dropped accordingly. After they had lost an average of 124 pounds their calorie requirements had dropped by an average of 28 per cent to become lower than those of normal-weight people. As they lost weight their bodies were using any available food more efficiently.

Although irritating to the dieter who wishes to lose weight, it makes perfect sense to the body which is responding to an evolutionary history of dealing with the lack of food. Excess food is still only a relatively recent development, and the desire to be thin by rejecting food makes no sense to our sense of survival.

So, even if dieters are managing to eat less food than non- dieters and less than they would do if they were not dieting, dieting reduces their metabolic rate. Any food eaten is used more efficiently and the need for metabolising fat is minimalised. To lose weight and maintain this weight loss, dieters have to eat less consistently, and to compensate for a decreasing metabolic rate they have to eat less and less over time.

But what about the times when dieters are eating more than non-dieters and perhaps even eating more than they would do if they were not dieting at all?

... andjoyohoxing