Why Do Diets Fail?

Most dieters regain their lost weight. Scientists say the newly discovered appetite-stimulating hormone ghrelin is what makes this happen.

Jamie Cohen writes in abcnews.com that the hormone, which is secreted in the stomach, sends messages to the brain that fluctuate throughout the day, depending on how full the stomach is. Ghrelin produces hunger by rising shortly before meals and dropping soon after.

A team at the Veterans Affairs Puget Sound Healthcare System and the University of Washington compared blood samples of 13 obese patients, before and after six months on a low-fat, low-calorie diet, with those of five patients who had undergone gastric bypass surgery. While dieters lost 17 percent of their body weight, their ghrelin levels rose by 24 percent. In contrast, gastric bypass patients dropped 36 percent of their body weight yet their ghrelin levels were 72 percent lower than the dieters.

Unlike ghrelin levels in the diet group, the hormone levels in the surgery group did not increase and decrease in relation to meals. In fact, “ghrelin levels not only failed to rise but dropped profoundly,” says Dr. David Cummings, an endocrinologist at VA Puget Sound Healthcare System and the University of Washington in Seattle. The reason is that bypass surgery shrinks the stomach to only 5 percent of its original size by rerouting the way food passes through the digestive system. The tiny new stomach can hold only two teaspoons of food, which then travels into the small intestine. It?s the presence of ingested food in the stomach that activates the ghrelin cells there. The permanent absence of food in the stomach eventually suppresses ghrelin production.

After a diet-induced weight loss, researchers observed a rise in blood-ghrelin levels. In addition to increasing food intake, they discovered that the hormone also slows down the body’s metabolic rate. It?s as if Ghrelin wants us to get back to our former weight, even if we were dangerously heavy.

Ghrelin is part of the body’s built-in defense mechanism to protect against starvation. Over the course of evolution, natural selection developed genes that in plentiful times put weight on our bodies in order to prepare for times of famine. During famines, our metabolism decreased in order to keep weight on our bodies, says Cummings. Although our lives have changed, our hormones still work the same way they did in prehistoric times.

This is why “weight loss occurs fast at first but then slows as the body fights vigorously to regain this predetermined set point,” says Dr. Michael Meguid, editor-in-chief of Nutrition magazine and director of surgical research at the State University of New York’s Upstate Medical University in Syracuse, N.Y.

Ghrelin triggers hunger, says Frank Chae, assistant professor surgery and head of obesity surgery at the University of Colorado Health and Sciences Center in Denver, and “Hunger is the chief reason for which most dieters quit dieting and regain the excess weight.”

So is the only way to lose weight to have our stomachs stapled? Not so?researchers believe they can use ghrelin to help ordinary dieters lose weight and keep it off. One possibility is the development of a drug that, like gastric bypass surgery, blocks the production of ghrelin. You can be sure that drug manufacturers are rushing to develop it right now.

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Scientists at the U.S. Department of Energy’s Brookhaven National Laboratory have discovered that the sight of food causes the brain to react with pleasure. This looks very different from the way the brain lights up when people actually eat. “This shows us why all the advertisements about food are so powerful and why we are having problems with obesity in this country–because we are constantly being bombarded with food stimuli,” says Dr. Nora Volkow, the psychiatrist who led the study.

If people are aware of what?s going on they may be able to consciously to block the effects of advertising, the smell of bread in the supermarket and other stimuli that make people want to eat when they know they shouldn?t.

Volkow and her colleagues used positron emission tomography (PET) brain scans to measure dopamine levels in 10 hungry volunteers. Dopamine is a chemical associated in the brain with pleasure. “They were all of normal weight,” Volkow says. “We asked them what their favorite foods were. Then first we studied them under a condition where there was no stimulation of food –we just asked them to please tell us about their family genealogy.” While this was going on, each volunteer underwent a PET scan. This gave the researchers a baseline measurement.

“Then we exposed them to the food they said they liked. But we told them they wouldn’t be able to eat it,” Volkow says. “We were being a little mean for the good of science.”Dopamine levels shot up, which Volkow says is normal.

“It is obviously a mechanism by which nature ensures that we actually consume food when food is available,” she says. “We never know when food is going to be available. Well, now we do because we have (convenience stores). But when we were evolving we didn’t, and when there was food accessible you had to eat it. Unfortunately, we really have created a system where we are flooded with information about food.?

Trying to make their results easier to measure, they gave their volunteers Ritalin (methylphenidate), which is given to children with attention deficit hyperactivity disorder. It can amplify the effects of dopamine in the brain, and it increased the responses of the volunteers to food. “Methylphenidate is known to take away your appetite,” she says. “It’s a problem because children don’t want to eat while on methylphenidate.”

So why did it increase the response of people who were shown images of food? Volkow thinks methylphenidate actually increases appetite, but only when food is presented under unusual circumstances. She says, “So if you want your child to eat while on Ritalin, try to give him the food in non-regular way. Don’t sit him down but present him with food that he is not expecting to have and then entice him to eat. Give him a novelty.”

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We’re spending about $222 billion on dining out each year, and the Center for Science in the Public Interest says this is becoming a dangerous habit. The non-profit group makes some surprising claims about the nutritional value of typical restaurant dishes.

“More than half of Americans are overweight and it’s no coincidence that we are eating out in record numbers,” CSPI?s Jayne Hurley says. “More restaurants are serving huge portions of high-calorie food. An entree or appetizer or dessert that is less than 1,000 calories is tough to find. That’s half of what you need for the whole day.”

CSPI nutritionists spent nine years and several hundred thousand dollars analyzing about 250 menu items. They examined national chains like Bennigan’s and Applebee’s, as well as family-style, Chinese, Italian, Mexican, Greek, seafood, steakhouses, pizzerias and some fast food restaurants. They also looked at mall food, drinks and movie snacks. The average person needs about 2,000 to 2,500 calories a day, containing about 65 grams of fat.

One of their most disturbing discoveries about restaurant food was the huge amount of calories and fat in appetizers, Hurley says. Some appetizers contain over 3,000 calories. An appetizer of deep-fried onions, for instance, has 2,000 calories. Buffalo wings have 1,000 calories.

A plate of cheese fries from the Outback Steakhouse chain was the worst, with over 3,000 calories and 217 grams of fat, including 90 grams of saturated fat. This one appetizer contains the maximum amount of saturated fat that a person should eat in four days. “It’s like starting your meal off with two T-bone steak dinners with Caesar salad and baked potatoes and butter, for one person,” Hurley says.

If you are going to eat pizza, the wisest thing to do nutritionally is to stick to one slice of regular cheese pizza, which contains half the day’s supply of saturated fat. “It’s not the crust ? it’s the cheese,” Hurley says. “And when you go to the extra cheese and the toppings you have a big problem.”

The Pizza Hut Big New Yorker Sausage pizza contains 570 calories per slice, along with 33 grams of fat and 14 grams of saturated fat. That amounts to three-quarters of a whole day’s suggested caloric requirements. In terms of health value, the pizza slice is worse than a Big Mac from McDonald’s. But while most people wouldn’t eat more than one Big Mac, almost everyone has more than one slice of pizza. Hurley suggests that pizza lovers order half cheese, and choose vegetable toppings, which cut down on calories and fats. They should also avoid stuffed crusts.

At Starbucks, a Venti White Chocolate Mocha with whipped cream contains 600 calories, 25 grams of fat and 15 grams of saturated fat. That is the equivalent of a Quarter Pounder with Cheese from McDonald’s. If you add a scone, that extra snack adds 530 calories, 26 grams of fat and 16 grams of saturated fat. That is the equivalent of a Quarter Pounder. You can easily reduce the calories by asking for skim milk and skipping the whipped cream. A latte with skim milk is only 150 calories and a cappuccino with skim milk is only 100 calories.

A tuna salad sandwich might seem like a healthy choice, but the tuna is usually drowned in mayonnaise, and that is where the problem is. An average tuna sandwich has about 830 calories, 56 grams of fat and 10 grams of saturated fat. If you add potato chips, that equals 1,000 calories. At Subway, a light mayo version of the tuna salad sandwich is about one half of the calories.

A chicken Caesar salad may sound healthy, but it isn?t. A typical one contains 660 calories, 46 grams of fat and 11 grams of saturated fat. Most of the fat is in the salad dressing, because restaurants put too much on. Try ordering the dressing on the side, or asking for less of it.

Hurley says restaurants should have to put nutritional values on their menus. The big chains already have that information, and they should give it to consumers, so that they know how what they?re eating.

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Household chores are included in the 30 minutes per day of moderate physical activity recommended by the U.S. government as part of a healthy lifestyle, but researchers in England say there is no evidence that it has any health benefits. Shah Ebrahim and colleagues at University of Bristol recruited 2341 women between the ages of 60 and 79 from 15 British towns to fill in questionnaires about their activity levels. The team also gathered information on the women’s weights, medical history, and heart and lung function.

Housework turned out to make a huge contribution to whether or not most women met the U.S. health guidelines. More than two-thirds of the women were considered healthily active if housework was included, but 4 in 5 were not sufficiently active if it was removed.

Regular physical activity such as brisk walking and cycling significantly reduced average weight, pulse rate and fitness. But people who spent two and a half hours a week on housework scored the same on a series of health measures as those who did no exercise at all. “Housework doesn’t seem to count”, says Shah. “I would strongly recommend that women share the housework with their partner and use the time afforded to do some more interesting and beneficial activity.”

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