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.