Low Calorie Diets have risen in popularity in the past 20 years because of the rise in obesity in the USA. Obesity affects more than 30 percent of U.S. adults, and is fuelling an industry dedicated to low-calorie foods and drinks, diet and slimming aids. thats over 60 million people, are obese.

A low calorie diet is one that restricts the amount of calories you eat in any given day to 1500 or less. Low calorie diets are not to be mistaken with Very Low Calorie Diets (VLCDs) which are commercially prepared formulas, such as meal replacement shakes and soups of about 800 calories that replace the entire usual food intake for several weeks or months.

Studies have shown that low calorie diets can produce weight loss in obese patients of about 3 to 5 pounds per week, for an average total weight loss of 44 pounds over 12 weeks. Such a weight loss can rapidly improve obesity-related medical conditions, including diabetes, high blood pressure, and high cholesterol.

However, low calorie diets carry many health risks, and like most diets, have a 95% failure rate. When you go on a low calorie diet, youre most likely to suffer from the starvation response. This is when your body realises that its not getting enough energy, and starts to preserve its supply of fat by burning fewer calories. In addition, when you reduce the amount of calories you eat, your brain receives signals to eat more, your appetite is stimulated and you have feelings of hunger and deprivation.

While low calorie diets can result in weight loss in the first few weeks and months of starting the diet, the majority of the weight lost is not fat. This is because low calorie diets do not provide sufficient energy to fuel the bodys basic functions such as breathing, circulation, and digestion etc. In order to provide the fuel to keep itself alive, the body breaks down muscle tissue, which is easily convertible into glucose, and is easier to access and break down into energy than fat.

In effect, low calorie diets reduce the amount of lean muscle tissue in the body, which has a knock-on effect of reducing the basal metabolic rate. Lean muscle tissue is metabolically active, meaning that the more lean muscle tissue an individual has, the more calories are burned. The reduction in lean muscle tissue also reduces the bodys ability to burn fat.

When you finally lose the weight and start eating normally, your body can no longer burn calories at the rate it did before your diet because you now have less lean muscle tissue! You become locked in a vicious cycle of dieting and weight gain - simply because your body breaks down muscle for glucose before it breaks down fat. Although you might only end up gaining back the original weight you lost, you are will end up fatter because you have lost lean muscle tissue and gained back fat.

The result of the loss of lean muscle tisssue and the weight gain arising from it is termed the Yo-Yo effect. Many dieters, when finding that they have regained the weight they have lost, embark on another diet, which plunges them further into lean muscle tissue loss.

So, what is the solution to permanent weight loss? To lose weight effectively, you need to consume enough energy to burn fat, and eat the right foods to maintain your level of lean muscle tissue. A sensible balance of a healthy diet and moderate exercise is more effective in achieving a permanent weight loss than low-calorie diets.