Positive Health Online

Why Diets Don't Work

Most weight loss diets do little to change body fat. You can lose weight with almost any of the popular weight loss diets, at least initially. However, many of these diets are designed to achieve their weight loss through a loss of water and lean muscle tissue, both of which are normal and important components of the body. Since muscle weighs more than fat, any loss of muscle will give a faster decrease in the reading on the scales than a true loss of fat.

Most people like the psychological boost of being able to say how much weight they have lost after a week or two of the diet, but the overall effect when most—or all—of the lost weight inevitably returns is depressing. Many people think they have failed once again, and instead of blaming the diet think it was their fault. Some distance themselves from feelings of guilt and failure by blaming it on their metabolism.

There is no mystery to the sudden initial drop in weight with almost all fast weight loss diets. Most achieve it by restricting carbohydrates. Once you cut down on bread, potatoes, pasta or rice, your body is no longer supplied with the major fuel for its muscles. Over the next few days (or hours, if you exercise vigorously), the stores of carbohydrate in muscles (known as glycogen) are used up. Since the average person has 500-700 grams of glycogen in their muscles, the loss of this accounts for some of the initial weight loss. However, every gram of muscle glycogen is stored with nearly three times its weight in water, so the total loss of weight is quite substantial. The muscles have lost their main source of fuel—and you feel tired and unable to continue with exercise—but the scales show a fairly dramatic result.

Along with the water loss from muscle, any very low kilojoule or low carbohydrate diet will cause the kidneys to excrete more sodium and potassium than usual. These mineral salts are lost in urine and take some of the body's water with them, causing a further loss in weight. Losses of other minerals such as calcium, magnesium and phosphorus may occur too, and the loss of these, as well as the loss of water, may be responsible for the muscle cramps that often accompany stringent efforts to lose weight.

Many very strict diets fail to supply enough food to last until the next meal. Without enough food, the blood glucose level falls and the body's first attempt to reverse this situation is to send out hunger pangs. Food quickly restores blood glucose and the hunger pangs disappear. If you do not eat anything (and most strict diets forbid anything between meals), the feeling of hunger disappears after a few minutes because the body quickly converts some glycogen stored in the liver to glucose. Once that has been used—usually in about 30 to 40 minutes—you feel another hunger pang. If you again ignore it and do not have something to eat, you use up more of your liver glycogen. This process is repeated several times until the liver glycogen supplies are exhausted.

The body needs to maintain a basic level of glucose in the blood because it is the only fuel the brain can use under normal conditions, and the body always tries to protect the brain. So, ever resourceful, the body puts its next survival mechanism to work and breaks down protein to replenish its flagging blood glucose. With very strict diets, or with diets that do not include enough protein and kilojoules to last you between meals, lean body tissue (mostly the body's muscle) is broken down to replenish blood glucose. This leads to further weight loss—but there have been many reports of people on very strict low carbohydrate diets suffering permanent health problems, even death, because the protein has come from some vital structural tissue. Kidney damage is also possible under these conditions and is the major reason why most strict diets warn people to drink plenty of water.

Many mildly overweight people ignore the warnings against very low carbohydrate diets because they assume that damage will only occur in people who are massively obese. In fact, most deaths in dieters have occurred in people who were only slightly too fat. The reasons are not yet understood.

Muscle is dense and heavy, so losing muscle produces a fast weight loss, at least initially. Once the body breaks down protein to convert it to glucose, it must get rid of the nitrogenous waste products. This occurs through the kidneys and requires a lot of water, leading to further weight loss, but also partial dehydration in those who do not drink enough water. Loss of muscle tissue may give a good-looking response on the scales, but not on the slimmer!

Lean muscle tissue is the firm part of the body that keeps you looking good. The haggard look many people experience when dieting is partly due to loss of lean muscle tissue. Extreme fatigue and dislike of exercise occur because the muscles have lost their fuel supply (glycogen). It is biochemically impossible for the body to spare its lean muscle tissue and convert fat into glucose instead. Some sellers of supplements claim their products help this happen, but they do not understand the biochemical impossibility of it.

Reducing the body's glycogen, muscle and water is the basis for almost all fast weight loss diets. Whatever name they are given, an analysis shows they are low in carbohydrate, and hence cause fast weight loss from muscle loss. The body cannot burn fat fast, and the fast weight loss so many people desire is impossible without a loss of lean muscle tissue.

extracted with permission