Well, you figure it might be worth a try, since you're still fighting that bulge. But you may be starting to wonder: If these diet-book authors are so smart (and some do have medical degrees), how come their diets haven't worked for you?
The fact is that fad diets usually don't work in the long run. Experts say they tend to produce quick results that don't last. Running after the latest diet trend may be the only form of exercise that actually doesn't help you lose weight. It's also something of a national obsession, to judge from the success of diet books and other products aimed at the weight conscious.
Of the four top-selling paperbacks on the Feb. 27 New York Times bestseller list in the "Advice, How-to and Miscellaneous" category, for instance, three were diet books, all touting a routine of low-carbohydrate, high-protein foods. At the top stood Dr. Atkins' New Diet Revolution, by Robert C. Atkins, M.D., in its 176th week on the bestseller list.
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On the fat track
The American Dietetic Association says Americans spend more than $33 billion a year on weight-control products and services. It estimates that about 25% of men and 45% of women are, at any given time, trying to lose weight.
Yet Americans just keep putting on the pounds. According to the National Centers for Disease Control and Prevention, 43% of the U.S. population was overweight in the early 1960s. That number had risen to 55% by the mid-1990s. The direct cause of this trend is no mystery, either. People are simply eating more and sitting around too much. The American Dietetic Association says only about a fifth of the population gets enough exercise to help control their weight.
"The big problem with Americans is not losing weight, but keeping it off," says Nancy Bloom, a registered dietitian in the San Francisco area. Lasting weight loss takes "some work and education," she says.
A fad diet, as dietitians use the term, is any scientifically untested eating plan that sharply restricts the kinds of food you eat while promising dramatic weight loss. Some have a link to scientific fact, though they make claims that go way beyond the evidence. Others (like diets that promise weight loss from the interaction of certain foods) are based on pure myth.
But all of them, in some way or another, are at odds with mainstream thinking, which holds that the healthy way to lose weight and keep it off is to maintain a balanced diet with a lower overall intake of calories and to exercise regularly. Fad diets, as a rule, do not require exercise.
Get-thin-quick schemes
What makes fad diets popular is that they work in the short term. People who follow them can lose weight quickly, but not through any metabolic magic. What's going on is much simpler: Because of the sharply restricted food choices, the dieter is taking in far fewer calories than normal.
The low-carb diet works a bit differently: When the body is deprived of the glucose (sugar) in carbohydrates, it starts converting fat into substances called ketones to use as fuel. High-fat, low-carb diets can lead to ketosis, an oversupply of ketones. Fruity breath is one infamous symptom of this. If Ketosis continues for a long period of time, serious health problems, such as vomiting and dehydration, can occur.
In a low-carb diet the body also starts turning the liver's store of the carbohydrate glycogen into glucose, which is the body's main source of fuel. As Cornell University nutritionist David A. Levitsky notes in an article at the university's Food and Nutrition Web site, liver glycogen has lots of water molecules, so the body loses water weight as this substance is converted. This accounts for the majority of early weight loss seen in these types of diets.
Finally, on a high-protein, low-carbohydrate diet, you tend to lose your appetite.
"Weight loss during the first week on a low-carbohydrate, high-protein diet is impressive," Levitsky concludes. But the loss is not sustainable, he says, because most people find they can't stay on the diet. They tire of the diet and soon go back to their old eating habits.
Low-carb and other fad diets also raise safety concerns, such as their potential impact on the kidneys. But it's hard to study their long-term impact when most people don't stay on them very long. The main criticism against them from dietitians is that they're just too restricted and unbalanced to be a sound long-term nutrition plan. People naturally want to eat a variety of foods, they say, and fad diets deny them this variety.
The pitfalls of fad dieting
And even if they do no direct physical harm, fad diets can get in the way of healthy weight management by wasting a dieter's time and maybe sapping the spirit. If they're the only way you've tried to lose weight, and you haven't been successful, you might give up.
Laurel Mellin, a registered dietitian and associate professor of family medicine and pediatrics at the University of California School of Medicine, says fad dieting creates a vicious circle: "Realistically, it doesn't matter whose diet it is," Mellin says. "They'll blow it and get the weight back. Then they blame themselves and get more depressed and gain more weight."
Mellin says there's no mystery to losing weight successfully: You just eat a little bit less and exercise daily. "Even as little as 50 calories a day less in eating produces significant weight loss over a year," she says.
All it takes, really, is patience. But that's just the problem for many people, who would rather get quick results even at the cost of having to repeat the same ordeal over and over again.
Meanwhile, the people promoting fad diets get the best of both worlds: A public obsessed with being thin and unwilling to wait for healthy weight loss, and a cycle of diet failure that keeps them overweight — and eager to try the next new diet when it hits the bookshelves.
Here are some problems to watch out for when trying to lose weight:
Fad-diet risks
- You may experience long-term health problems from eating an unbalanced diet. The high-protein diet, for example, calls for high-fat foods, while others leave out essential nutrients. The result: possible damage to the kidneys, heart or other organs.
- By setting unrealistic weight-loss goals, you are more likely to fail, which might discourage you from trying even a reasonable diet plan.
- If your weight is truly a health problem, you're prolonging the harm it can cause you by not finding a way to keep the weight off.
Weight-loss barriers
- You can't remain on a diet, either because it makes you miserable, or you get tired of the limited types of food you can eat.
- You don't develop a regular exercise routine.
- You don't deal with behavioral causes of overeating, such as eating when you're not really hungry.
- You may have a medical or psychological condition that calls for professional help.
- You lose weight for the wrong reason — to fit into a particular dress, for example, not to improve overall health.
- You are too intent on losing weight quickly, not on managing weight and cutting the pounds slowly.
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