Will the Dukan Diet Turn Kate Into a Bridezilla?

Be prepared for the newest trend in weight loss. It's called the Dukan diet. Carbs are out, yet again. Do you want to lose pounds? Follow this high-protein diet that insists you eat only protein for an entire day once a week (Thursday is recommended), and say good-bye to most fruits and vegetable every day. Alcohol? Don't even think of it. Want to mop up the steak drippings with a piece of crusty bread? Dream on. It is not going to happen.

Does this diet sound familiar? Sure. It is the Atkins diet with a French accent -- actually, make that a French-British accent since the diet is now taking over the U.K. With the speed of a trans-Atlantic flight, it is coming soon to your American neighborhood. We are learning about the diet because the popular media announced that Kate Middleton and her Mum are on it.

The diet will work. Why wouldn't it? All of us will lose weight eating very lean protein in tiny portions, eliminating most fat, and not allowing a morsel of carbohydrate to pass our lips. If you go to the Dukan website and read the questions addressed to the diet authority during the evening chat, you will see how careful the dieter must be. Even a food as low in calories as an artichoke was forbidden because it contained too much sugar! The neat thing about this diet is that anyone who lost and then gained weight on the Atkins diet now has a second chance to lose and gain back the weight again.

If Kate is on it and I hope not (she is certainly thin already) I am concerned that bad things will happen to her good mood. Several years ago, I received a frantic phone call from a young man about to be married. "Help me," he begged, "please tell my fiancée to go off the Atkins diet. Her entire personality has changed and I am not sure I can marry her."

After he calmed down, he told me that he was to be married in five weeks to someone he had been dating for a few years. She wanted to lose weight quickly and insisted on following the no-carbohydrate phase of the Atkins diet until the wedding. She did lose a considerable amount weight but, according to my caller, he couldn't bear being with her. My protestations that she was just going through pre-wedding jitters was not reassuring. "No, it isn't that," he insisted. "I could understand if she was anxious or worried or obsessed with some wedding detail. She is simply nasty."

I offered to call her but she refused to speak with me. The wedding never took place.

Changes in mood following carbohydrate deprivation due to the depletion of serotonin in the brain are not surprising. Many years ago, the predecessor to the Atkins diet was being followed in the Boston area. Patients were allowed to eat only very lean protein and were quite successful in losing weight. But they were irritable, had trouble sleeping, and angry. And as soon as they met their weight loss goal and were allowed small quantities of fruits, vegetables and some starch, almost all of them binged and gained back their weight.

We were curious about the effect of not eating carbohydrates on the ability of their brains to make serotonin. So we studied rats who were following a similar diet. The laboratory animals were able to eat as much fat and protein as they wished but no carbohydrates. After a couple of weeks we compared the amount of tryptophan (the amino acid that makes serotonin) in their brains with the amount of tryptophan in the brains of rats that were eating carbohydrate all along. The brains of the carbohydrate-deprived rats had abnormally low amounts of tryptophan. This meant that their brains were unable to make normal amounts of serotonin.

So what, you may be thinking? Who cares how much tryptophan or serotonin I have in my brain ... at least I will lose weight . But this weight loss comes at a cost, especially for female dieters. Women have about 25 percent less serotonin in their brains than men. This has been shown many years ago by several laboratories and it is thought to account for the higher percent of depressive illness among women. Serotonin is not a 'throw away' neurotransmitter that we can make or not make without any ill consequences. In addition to depression, low serotonin activity has been linked to the pain of fibromyalgia, difficulty in falling asleep, depression, difficulty focusing, loss of energy, as well as the anger and fatigue of PMS. Low serotonin may also be involved in binge-like eating after carbohydrates are finally put back into the diet. (This happened with our rats.)

The natural way to make serotonin is to eat simple or complex carbohydrates except fruit. But of course if the diet forbids carbs, then serotonin levels drop.

I doubt if Kate will exhibit the kind of behavior seen on some reality TV shows about bad-tempered brides. But I suspect that as the inevitable stresses of the royal wedding increase, lack of this calming brain chemical may make them harder to endure.

Weddings, mothers-in-law to be (even those who are not Queen), and life in general pose real or potential obstacles to weight-loss attempts. Serotonin helps take the edge off of these stresses and helps us cope with what we cannot change.

If Kate is listening, my advice is to have tea with your future mother-in-law, eat a fat-free biscuit, and enjoy the serenity that comes with new serotonin.