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PART ONE

THE BRAIN-WEIGHT CONNECTION

CHAPTER ONE

Solving the Carbohydrate Riddle

Eating carbs and losing weight seem like opposites that never attract. How can you eat the carbohydrates you love when you hate the weight you gain when you eat carbohydrates?

This love-hate relationship often dictates how you try to lose weight. You avoid carbohydrates by going on a high-protein diet. When you go off the diet, carbohydrates are the first foods you reach for and you overeat. Or, when you are stressed, all of your good intentions to watch your carbohydrate intake are tossed aside. It's as though an uncontrollable force pulls you toward anything that is sweet or starchy--or both. As the stress mounts and the £ds are added on, you feel powerless to stop eating the carbohydrates. What are you supposed to do?

Maybe you never had a weight problem until, like millions of others, you began to take antidepressants. For a reason you can't fathom, you never feel full, no matter how much you eat. Suddenly carbohydrates are the only food you really want. And as you give in to this new craving, your weight goes up. What are you supposed to do?

At last there is an answer, based on decades of research and clinical experience. You must eat carbohydrates to lose weight and you must eat carbohydrates to maintain the loss.

THE CARBOHYDRATE-SEROTONIN CONNECTION

As hard as it may be to believe, carbohydrates are as essential for weight loss as gas is to a car. They not only drive the system that controls appetite, they also control emotional eating and mood.

At this point many of you who have been told that the road to weight ruin is paved with carbohydrates (especially the yummy ones) are likely reading this in disbelief. How can it be? Don't carbs bulk up fat cells? Shouldn't they be avoided, or at least limited to brown rice, a few leafy vegetables, and occasionally some fruit? How can it be possible to eat pasta, potatoes, rice, and even bread if you want to lose weight? And how can you stop overeating carbohydrates once you start?

It is not only possible to eat carbohydrates and lose weight, it is essential to do so. The reason lies within your brain.

Eating carbohydrates triggers a process involving the hormone insulin, an amino acid called tryptophan, and a barrier between the blood and the brain. The net result of this process is the production of a brain chemical called serotonin.

Serotonin is the switch that turns off your appetite. It is the "I have had enough to eat" switch. Serotonin is also the control that restores your good mood after minor and major stresses erode it. When produced consistently and regularly, serotonin prevents the tendency to eat impulsively when stresses occur.

Nature seems to have tagged serotonin as the only food-dependent brain chemical. At the same time, nature did you an enormous favor. By being able to manufacture serotonin by eating sweet or starchy carbohydrates, you can tap into a built-in appetite suppressant and mood regulator.

That's why the Serotonin Power Diet is based on maximizing serotonin production. Our carbohydrate-friendly, serotonin-producing diet will satisfy your appetite even though you will be eating fewer calories. If antidepressants are making you overeat, our diet will give you control over your appetite. It will take away the mental fatigue that keeps you from exercising. And the Serotonin Power Diet will also buffer you when you respond to stresses that otherwise would have you setting a world record for hand-to-mouth eating.

CARBOHYDRATES 101

Carbohydrates come in two basic forms: simple and complex. The simple ones, also called sugars (as in table sugar, or sucrose, and milk sugar, or lactose), are made up of one or two molecules. They are digested very quickly into the simplest carbohydrate of all, glucose. Glucose, which circulates in the blood, is the sugar used by muscles for energy. When you exercise, your muscles use a stored form of carbohydrate called glycogen. Marathon runners "carbo-load" before a race to increase the amount of glycogen in their muscles.

Complex carbohydrates are made up of the same molecules, but in long chains with branches. You know these carbohydrates as starches and eat them as potatoes, pasta, bread, cereal, rice, cornmeal, oats, barley, millet, rye, and other grains. Beans and lentils, although higher in protein than some other carbohydrates, are also included in this family of starches. Complex carbohydrates are also digested into the simplest carbohydrate, glucose, but it takes longer for them to reach this state because of their complexity.

Thus, all carbohydrates end up as glucose as soon as they leave the intestines and enter the bloodstream. Fruits, which contain fructose, are the exception. Fructose must go through an additional biochemical process in order to be converted into glucose.

SCIENCE EXPLAINS THE BRAIN-SEROTONIN CONNECTION

At the Massachusetts Institute of Technology (MIT) in the 1970s, Richard Wurtman, MD (Judy's husband), and one of his students made groundbreaking discoveries about the connection between the brain, serotonin, and carbohydrates. They discovered that after animals ate carbohydrates, their brains contained more serotonin.1-4

The connection between carbohydrates and serotonin was puzzling and quite unexpected. It was already known that serotonin is made when the amino acid tryptophan enters the brain. It was also known that tryptophan is one of many amino acids that make up protein. For instance, tryptophan is found in protein foods such as steak, fish, chicken, and eggs. Tryptophan is not found in carbohydrate foods such as potatoes, bread, and pasta. So it seemed logical that eating protein, not a carbohydrate, would prompt serotonin production.

But that's not what happened. When laboratory rats were fed a protein meal (such as the protein in milk), their brains made no new serotonin. And when protein was added to a meal containing carbohydrate, no serotonin was made either, even though the rats were eating carbohydrate. It seemed as if eating protein prevented serotonin from being made.

After the scientific version of "Huh?" was exclaimed, the research team examined how tryptophan gets into the brain from the bloodstream. They knew that there is a barrier around the brain that controls what actually enters the brain from the bloodstream. Some of the substances the brain needs enter through certain "doorways." It was known that tryptophan enters the brain through a particular doorway along with a group of amino acids called neutral amino acids. These amino acids compete with each other to get into the brain through this door the way shoppers compete with each other to be the first ones in the store for the day-after-Christmas sales. The bloodstream fills up with amino acids after protein is eaten and digested. So it seems logical that this would be when a lot of tryptophan gets into the brain. But just the opposite happens. Very little tryptophan gets into the brain because there is less tryptophan in protein than other amino acids. So when the amino acids cluster around the doorway to the brain, the larger number of neutral amino acids squeeze tryptophan out and send it to the back of the crowd. Although some tryptophan may get into the brain, it is not enough to make new serotonin.

This still left the question, How does tryptophan get into the brain so easily after carbohydrate is eaten? It is as if the manager of the store plucks tryptophan from the back of the crowd and sends it through the doorway first.

When any carbohydrate is eaten, with the exception of fruit, the hormone insulin is released from the pancreas. (Only trivial amounts of insulin are released in response to dietary fructose.) As digested glucose enters the bloodstream, insulin sends it into the organs of the body, where it is used as energy. Within several minutes the level of glucose in the blood returns to pre-meal levels.

As insulin pushes the glucose into the organs, it also sends amino acids out of the blood into the organs. Tryptophan is also sent away--but not as fast as the other amino acids. Think of that crowd in front of the store. The people pushing to get in melt away, leaving only one person to walk easily through the doorway. Tryptophan no longer has any difficulty getting into the brain. Once in the brain, it is quickly converted into serotonin.

Dr. Richard Wurtman, Judy, and their colleagues concluded after further research that eating carbohydrate is the only way tryptophan can get into the brain to make serotonin.

Why is this important for you to know? Because, as Judy's later research found, as serotonin is made it begins to turn off your appetite and make you content with eating less. It turns on your good mood and makes you resistant to stress-triggered overeating. And serotonin can make you feel more energetic.

THE SEROTONIN-APPETITE CONNECTION

It wasn't always obvious that serotonin is involved in regulating eating. People used to believe that when the stomach filled up, eating would stop. (Of course anyone who has consumed dessert despite feeling stuffed from the main course would dispute this assumption.)

After the initial serotonin studies were completed, Judy and her colleagues at MIT conducted further research to determine if cravings for sweet and starchy foods were related to serotonin and carbohydrates.

The work was not done in isolation; much research done elsewhere in the United States and in Europe showed that the brain contained the master switch to turn off eating.

Judy's first set of studies on laboratory animals showed that when brain serotonin was made more active, the animals stopped eating.5-7 After animals were treated with drugs that increased serotonin's activity, their food intake was compared to that of animals treated with a placebo.

The treated animals stopped eating much sooner than the animals that did not take these drugs. These studies were done many times to make sure that the results were valid. It was very exciting to find that the brain, and not the full stomach, was able to turn off eating.

Then Judy's team wondered what would happen if animals did not have enough serotonin in their brains. Normally, laboratory animals eat a great deal of carbohydrate, so presumably their brains were able to make new serotonin at any time. Would the animals eat differently if their daily carbohydrate were taken away from them? Would the absence of carbohydrate and the absence of serotonin have any effect on how much they ate? Might they exhibit the animal version of a binge?

To find out, rats were given the same number of calories they usually received, but the food contained only protein and fat. They were not allowed to eat any carbohydrate. The rats stayed on this rodent version of the Atkins Diet for 3 weeks. Other rats were given normal rat food, which contained carbohydrate as well as protein and fat, for the same period of time. After the 3 weeks were over, both groups were given three dishes of food. One dish contained protein, the second held fat, and the third contained a mixture of starch and sugar.

The rats that had been allowed to eat carbohydrates in the previous 3 weeks continued to do so, taking a small amount of food from all three dishes.

Things were different for the carbohydrate-deprived rats. They binged on the carbohydrates, ignoring the protein and fat. Rats normally do not binge. Rats always control what they eat. Something had happened.

The research team found that there was very little tryptophan or serotonin in the rats' brains. The few weeks of a no-carbohydrate diet had prevented serotonin from being made. And as a result, not only were the animals eating more than they usually ate, they were actually seeking out carbohydrate. Was the brain telling them what to eat to restore depleted serotonin levels?

If so, the brain succeeded in this case. By the next day the formerly carbohydrate-starved rats were eating as they had before the experiment. It seemed that their serotonin levels were back to normal.

But was this also true of people? Would their serotonin levels and their eating also be affected by the lack of carbohydrates? To find out, human volunteers at MIT were recruited to go on a carbohydrate-free diet. Their blood was tested for amino acid levels that would tell whether serotonin was or wasn't being made in their brains.

The findings were not surprising. The blood tests confirmed that very little tryptophan could get into the brain to make new serotonin. And the lack of serotonin had an impact on how the volunteers felt. They craved carbohydrates constantly and complained about not feeling full, even though they were getting more than enough food.

But scientists have to be skeptical. Maybe the volunteers just missed the tastes and textures of carbohydrates, which would explain why they grumbled about not feeling satisfied. It might not have been due to the lack of serotonin at all.

The only way to tell whether their feelings of deprivation were caused by their brains or their taste buds was to change serotonin activity in their brains without telling them.

It was decided to see if the volunteers still had their cravings when serotonin activity was increased in the brain with a research drug. The volunteers were given either a test medication or a placebo without their knowing which treatment they were taking. If their cravings for carbohydrate decreased after being treated with the test drug and they felt as satisfied as they would have if they had eaten, the researchers could be reasonably sure that these feelings were due to changes in serotonin and not taste buds.

Several studies showed that volunteers treated with the placebo did not experience any decrease in their appetite or carbohydrate cravings. On the other hand, the volunteers who were treated with the test medication experienced decreased carbohydrate cravings. One volunteer said, "I used to polish off the leftovers before they were carried to the kitchen. But for a couple of weeks I couldn't even finish what was on my plate. I learned later that those were the weeks when I was taking the drug."

These experiments, and others like them, suggested that serotonin is the key to controlling appetite so that people can stick to the portion sizes of a diet without difficulty. Serotonin is also the key to minimizing cravings for sweet and starchy snack foods, the downfall of many a dieter.

And nature revealed the perfect diet tool to manipulate serotonin: carbohydrates. To lose weight, no drugs, supplements, or strange food combinations--or side effects--are necessary. Carbohydrate snacks, however, are welcome.

SNACKS: YOUR UNEXPECTED ALLY

From the studies' conclusions, we guessed that carbohydrate snacks would help control appetite, reduce cravings, and prevent overeating when emotionally upset. Before making the snacks an essential part of the Serotonin Power Diet, we tested our theory.

Studies were done with obese volunteers who wanted to lose weight. All of the volunteers were told they would be given one of two drinks that contained the same number of calories. One was composed solely of carbohydrate and the other contained carbohydrate and protein. They were told that one drink would increase serotonin and might cut back their appetite and food intake while the other would not likely have any impact.