How to weigh the competing claims of all those weight-loss plans

If you are thinking about a diet, you are probably pondering which side to choose in that huge divide splitting America -- low carb, or low fat. The fact is, it doesn't matter. Take "The Zone," a low-carb diet developed by Dr. Barry Sears. He calls for all meals to follow a 40-30-30 distribution -- 40% from carbs, 30% from protein, and 30% from fat. The formula lends gravitas, but it's not why you lose weight. If The Zone's initial meal plans and portions are followed exactly, you are eating 850 to 1,000 calories a day. Considering that the average daily calorie intake for adult Americans is 2,750 (that's 500 more than the government recommends, by the way), it would be almost impossible not to lose weight. Diets come and go. But we keep forgetting that there is only one way to successfully shed pounds: Burn off more calories than you take in. This is an ironclad law of bodily thermodynamics. Diets that claim you can eat as much as you want of certain foods and still slim down make it sound as if you'll never go hungry again. It's just not going to happen. The reason: It doesn't matter how your calories are ingested, only how many.

A calorie, which is a unit of heat, is the same whether it's contained in a slice of bread, a slab of steak, or a stalk of celery. There are 3,500 calories in a pound of body fat, so to lose a pound per week you have to burn off 500 calories per day more than you take in. On average, women need 10 to 11 calories per pound per day to remain at their current weight, and men need 12 to 14. Multiply your desired weight and your current weight by those numbers, subtract the difference, and you'll know how many calories you should cut.

Counting calories, however, is complex. Weight-loss expert Dr. Donald D. Hensrud of the Mayo Clinic in Rochester, Minn., says this is why diets fail. "People on diets consistently underestimate their calorie intake."

Consequently, most of the best-selling diet books throw calorie-counting out the window. Instead, they advocate sticking to certain food groups while eliminating or reducing others. That can be an easy way to cut calories, especially if you've been loading up on the carbohydrates, fats, or sugars that are banned. It is almost inevitable that if you cut out all carbs, for example, you will lose weight, because you are eating less food.

Many medical experts aren't wild about weight-loss plans based on food restrictions. A well-balanced diet combined with portion control is widely considered more healthful than one that eliminates certain foods. It can also be very hard to stick to a diet over the long term that cuts out entire food groups, and the long term is what matters. Studies have found that up to 95% of all dieters regain lost weight after a year -- and even add more pounds.

Still, food-restriction diets are enormously popular. They can be easy to follow and often produce immediate results. What's hard is wading through the competing claims from the many different plans. Each has its fervent adherents, and carries both pros and cons.

Low-carb diets are the current craze, led by the Atkins and South Beach diets. Fast-acting carbs such as refined flour, pasta, and white rice quickly break down into glucose (sugar) molecules in the blood, which in turn unleash a surge of insulin. High insulin levels can stimulate hunger, and low-carb advocates argue that you will eat less if you minimize insulin surges. Several studies have shown that this strategy is very effective in the first six months, but by the one-year mark, even Atkins researchers have found that the low-carb diets have just as high a failure rate as other weight-loss plans.

Medical specialists also worry about the long-term health impact. The Partnership for Essential Nutrition, a coalition of public-health groups that includes the American Obesity Assn. and Shape Up America!, recently did a survey of the scientific literature on low-carb diets. It concluded that these diets can lead to kidney stress, liver disorders, and gout and can increase the risk of heart disease, diabetes, and stroke.

On the other side are the low-fat advocates, such as the Pritikin Principle and Weight Watchers. This approach has been popular for well over a decade, as evidenced by the huge increase in low-fat foods displayed on supermarket shelves.

The medical Establishment particularly favors low-fat diets for their proven ability to help prevent heart disease. Also note that the National Weight Control Registry, which has collected data on more than 3,000 people who maintained a loss of 30 pounds or more for at least one year, found that the majority of successful dieters in the registry followed a low-fat program.

Keep in mind, though, that successful dieters are few and far between. It's tough to cut fat without feeling hungry all the time, and many people end up replacing fat calories with carb or sugar calories. Besides, some fats, such as nuts and olive oil, can be good for you.

Ultimately, the successful diet is the one that works for you. Figure out your current eating habits and lifestyle, and decide what changes you are most likely to stick with. If you are seriously overweight or have a health problem, a consultation with a doctor or a dietician is the best way to start. Then incorporate these rules, which apply to any weight-loss program:

-- Exercise. Even moderate exercise, such as a brisk walk three times a week, can make a big difference. Diet alone can take the pounds off, but exercise is the best way to maintain weight loss.

-- Eat "low-density" food. Fruits, vegetables, and whole grains have the fewest calories per ounce of any food, so filling up on them can quickly cut calories.

-- Eat slowly. It can take 15 minutes for the message to reach the brain that your stomach is full. Don't try to beat that clock.

-- Don't get hung up on reaching an "ideal weight." The Mayo Clinic's Hensrud warns that "weight goals can be elusive, and people are rarely satisfied when they reach them." Instead, focus on losing 10% of your weight. Once you have accomplished that, you may be inspired to keep going.

-- Avoid crash diets. The most successful weight-loss programs are gradual, usually a pound a week. Rapid weight loss can damage your health, and it's rarely sustainable.

Finally, don't think in terms of diet -- it's such a depressing word -- but lifestyle change. Remember, there was probably a time when you never supersized anything. Get back to that, and weight loss should follow.

By Catherine Arnst

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