Quick, but temporary weight loss! This time from France!

I just heard about a “new” diet: the Dukan diet. It’s from France! It promises four steps to permanent weight loss! It promises that people will lose weight while eating as much as they like! The problem is that this “new” diet isn’t really new. It’s just South Beach with a French accent. The quick results from the first phase aren’t from fat loss. Nor will your weight problem be permanently cured by the end of the program, regardless of what Dr. Dukan says. It’s just more false hope for desperate people.

Like many fad diets, the Dukan diet starts with a low-carb phase. As if by magic, this phase causes people to lose several pounds very quickly. Unfortunately, the weight that people lose so quickly does not represent fat. Instead, it represents the loss of the body’s glycogen stores. Glycogen is a starch that is stored in the liver and muscles. When the body needs quick energy, the glycogen is broken down into glucose, which is a sugar that is the body’s favorite fuel.

Like other carbohydrates, glycogen provides about 4 calories per gram of dry weight. However, the glycogen in the body isn’t dry. Each gram of glycogen absorbs about 2.7 grams of water. As a result, each gram of wet glycogen in the body represents roughly 1 calorie of stored energy. If you suddenly deprive yourself of carbohydrates, your body will run through its glycogen stores very quickly, releasing water that will leave the body through the kidneys. You would have to burn up almost 9 times as many calories to lose that much weight from fat.

The rapid weight loss that results from cutting out carbohydrates may be thrilling to the frustrated dieter, but it is meaningless. Nobody is overweight from having too much glycogen, and your body will replace that glycogen and water as soon as it can. What people really want to lose is fat. Besides, losing your glycogen can make you feel crummy. When marathoners “hit the wall,” it’s typically because they’re run out of glycogen.

So the first phase of the Dukan diet or the South Beach Diet will cause a quick but temporary and meaningless weight loss that could end up zapping your energy. If the Dukan diet eventually helps you lose fat, it does so by making your body think that you are starving or seriously ill. During a sudden fast, the body’s supply of carbohydrates is cut off. The body has to rely on its fat stores and the proteins in its tissues instead. A low-carb diet mimics this condition. The body may respond to this emergency by suppressing the appetite. The person may then lose weight the old-fashioned way, by taking in fewer calories than he or she burns up.

The Dukan diet is based on a lie: that people get fat from eating a high-carb diet. In reality, fat is fattening, and starches are slimming. That’s because starch, like glycogen, holds water. It’s actually hard to fatten yourself on starches. For example, consider what happened when the head of the Washington State Potato Commission went on an all-potato diet to protest the exclusion of potatoes from the federal Women, Infants, and Children (WIC) program. He lost 21 pounds in 60 days, even though he was eating about 20 potatoes per day. He also cut his total cholesterol by over a third, and lowered his blood sugar. In other words, he also improved his health.

A starchy diet works on both sides of the weight loss equation. You end up eating fewer calories, because the starchy foods are so bulky. Boiled starches often provide only 1 calorie per gram, whereas fat provides 9 calories per gram. You also end up burning more calories on a low-fat, high-carb diet, because you become much more sensitive to insulin. If you still manage to have a few calories left over, it’s hard for your body to store them as fat. You’d lose about 30% of the calories in the conversion process, so your body just generally revs up your metabolism to burn off the excess. You may end up doing more activity, or simply generating more body heat.

Forget Dukan’s false promises. The only proven way to achieve healthy, permanent weight loss is to switch to a low-fat, high-fiber, high-carbohydrate diet. That’s because it’s the kind of diet that is appropriate to the human body. If you simply train yourself to eating the right kinds of food, you can eat as much as you like and still stay slim.