The word ?calorie? appears to have a bad press, and there have been a lot of ill informed comments made about calories and whether calorie controlled diets are effective or not. Quite frankly, it is all said in ignorance. Whether you agree or not, the calorie is a measurement of energy and the calorie content of foods is what is calculated to be the energy value of these foods.

Once inside your body, that energy is either used up or converted to body mass. It is not necessarily converted to fat, since that extra weight could be in the form of muscle tissue. However, it is converted to body mass and so you can put on weight. The basic equation is that if you take in more energy than you use, then you add weight, and if you use more energy than you take in, then you lose weight. It is slightly more complex than that, but it is basically true.

That does not mean that if you eat a pound of dripping (the fat that drips off cooking meat) you will add a pound of weight. It is the calorific value of the dripping in terms of energy, whether measured in calories or in joules, that is the relevant factor, and if that is 4000 calories, which is about average for various types of dripping, then if you use up 4001 calories in exercise, you can safely spread your pound of lard on toast and eat it without putting on weight (you will have also to use up the calories in the toast).

It is the calorie equation that is important, and if this is negative then you will lose weight. You have to: it is a law of science! Whether your calories are in the form of cookies, candies, avocados (loads of them) or dripping, it is all the same. A meat calorie is the same as a vegetarian or vegan calorie. If you eat more than you use you put on weight.

Different foods contain different quantities of energy, or calories. If you buy a Big Mac you eat 570 calories, and 5 from your Super Pepsi. If the guy next to you has an English Muffin, he will have 140 calories. However, if he then goes home and slouches on the sofa watching TV and you go to the gym for a serious workout, he is liable to put on weight and you lose it. It's all in the equation!

However, you don't just use calories in exercise. Your metabolism is also important. In fact 65% - 75% of the calories you use in a day are used up by the body at rest: the metabolism that takes place 24/7 to keep you alive. The heartbeat, breathing and brain activity for example, all use up energy. So not all is doom and gloom, and you can burn up these calories even while you are sleeping.

However, there is another way to prevent the fat you eat from turning into weight. (Incidentally, if you exercise a lot, that weight will likely be in muscle mass, but if not then it will certainly be fat). You have a clue to the way that can be done in the first sentence of this article: ?dietary fat absorption?.

If the fat is not absorbed into the body, then it is not available to be metabolized into body fat. It will pass through the body unchanged. It is not the fat you consume that makes you gain weight, but the amount of that fat absorbed through your intestines. But how is it possible to selectively prevent the fat in your diet from being emulsified by the bile and absorbed through the intestinal wall?

By means of chitosan. This is a fiber that absorbs part of the fat from the food you have eaten and hides it away from your digestive system. It cannot be broken down into sugars and then into fat to add to your unwanted weight. However, because it works after your meal, you get to eat what you want ? that ?finger lickin? good? stuff you love, but don't suffer the consequences of failing to exercise to work it off. It's like you just ate lettuce without the fried chicken with the crispy fatty skin.

So what is this miracle substance, chitosan? Biologists would recognize the name as being associated with chitin, the acetyl-glucosamine polymer that forms the carapaces, or shells, of crabs, lobsters and other marine shellfish. Chitosan is formed by deacetylating the chitin and is mainly used to enhance the growth of plants, and also as a filtration aid. So what does it do to help to remove some of the fat from your diet after you have eaten it?

The mechanism by which it does this is not fully understood, and in fact is still disputed in some quarters. However, the proof of the pudding is in the eating and it appears to act according to the claims. There are two possible mechanisms, one of which is connected with the deacetylation of the chitin molecule. Because of this, the resultant chitosan molecule has cationic groups on the polymer chain. Cations are positively charged, and can react with acids, not the least of which are the bile acids that break down lipids (fats) to render them into a form suitable for absorption.

It is possible for the chitosan to react with the bile acids and prevent them from breaking down the fats into a condition that enables them to be passed through the intestinal wall. However, it has also been proposed that dietary fibers work by increasing the thickness of the boundary layer of the intestine through which the fats would have to pass. This would have the effect of reducing the lipid uptake.

It is also possible that since chitosan is a fibrous substance, it attracts the fats through its charge and absorbs them into a swelling ball of fats and fiber that is not only impermeable by the bile acids, but also passes through the intestinal tract unchanged and eventually excreted. In fact, there is not proof for any of these projected mechanisms, and all are theoretically possible. The fact is that it appears to work, but must be taken for several weeks for the effects to be noticeable.

It is possible to lose weight by dietary fat absorption, and whatever mechanism is used by chitosan, it is well worth trying if you like your fatty foods but also want to lose weight. Combine chitosan with a good exercise regime and you might find that you can control your weight whatever you eat. Chitosan is available over the counter at any health food store.