Forget fad diets. Get the facts on weight loss

By Ginny Graves

updated 8:32 a.m. ET June 6, 2008

For years, diet-book authors, weight loss gurus, and talk-show hosts have proposed a dizzying array of methods for shedding pounds.

There are juice fasts, raw-food programs, and hypnosis techniques; you can eat like a Frenchwoman, a caveman, or Jesus; and according to one recent book, you can even binge one day and fast the next ("Diet only half the time!"). So much for the common sense approach.

Tired of the hype, we turned to six diet experts for the real scoop. These anti-gurus have spent their careers studying what leads to real weight loss. Taking advice from experts who shun the limelight for the lab? That’s a fad we can get behind.

James O. Hill has studied successful dieters for 13 years to see how people lose weight — and keep it off. He is the director of the Center for Human Nutrition at the University of Colorado Health Sciences Center in Denver.

What's the biggest thing you've learned from successful dieters?
Weight loss happens in two stages that require two different approaches. First, there's the losing stage. That's all about food restriction. There's no particular diet that seems to be more effective than another one; it has more to do with individual preference — what you can stick with long-term. The weight-loss stage lasts an average of three to six months. We use 10 percent as a reasonable first goal. After six months, if you get there, you're a success story. If you haven't lost all the weight you want to lose in that time, you're probably not going to do it. If you still have a lot of weight to lose at that point, it's best to take several months to maintain the weight you've shed, then try another six-month diet.

Does exercise help?
Exercise has many health and emotional benefits, but it doesn't make a huge difference when it comes to weight loss. You can restrict your food intake by 500 to 1,000 calories starting tomorrow, but you have to work out for a long time, or at a very high intensity, to burn as many calories.

What's the second stage?
Maintenance. And that's when exercise becomes much more important. By burning a few hundred extra calories a day, you can eat a little bit more, which makes the diet tolerable and easier to maintain. Exercise helps you find a healthy balance between the calories you consume and the calories you burn. Successful dieters typically exercise a lot — 60 to 90 minutes a day. That's not just a short walk. They really prioritize daily, vigorous physical activity.

Are there other habits of successful dieters?
They tend to weigh themselves regularly to stay on track. The scale has been vilified, but it helps you stay focused. They also keep food diaries or count calories. And they are seven-day-a-week breakfast eaters. Eating a meal first thing in the day seems to help people manage hunger better. The typical pattern of obese people is to skip breakfast, have a light lunch, and eat a lot from late afternoon on.

Is there a point at which you're safe — when you'll keep off the weight you've lost?
After three years, you'll know whether you've settled into a routine that allows you to maintain the weight loss. By that point, most of the people in our study say they feel sure they're not going to regain the weight.

Ralph La Forge studies the role of exercise in weight loss and is managing director of the Lipid and Disease Management Preceptorship Program at Duke University Medical Center.

Why is it so hard to lose weight just by exercising?
Unless you're a serious athlete, you just don't burn that many calories. Most people overestimate the amount they've burned during a workout.

If exercise is part of your weight-loss plan, what's the best type to do?
Aerobic activity is far and away the best, for one simple reason: You burn more calories.

Doesn't strength training build muscle and therefore increase your resting metabolic rate?
That's actually a myth. You'd have to be totally ripped — like, bodybuilder ripped — to get a noticeable bump in your metabolism. Most people burn about one calorie per kilogram of body weight per minute, whereas a bodybuilder burns about 1.2.

What aerobic activities give you the biggest calorie burn?
Cross-country skiing — in nature, not on a machine — is the highest. Outdoor exercise is almost always more strenuous. You encounter variable terrain, which makes you work harder. Running comes after skiing, and walking on hills is probably third. In general, you burn more calories doing a weight-bearing activity that uses lots of big muscle groups. Swimming and biking usually aren't as good because they're not weight-bearing.

Are you better off doing a long, moderate-intensity workout or a shorter, high-intensity one? If you want to lose weight, stay at a moderate pace, because you can go longer and it doesn't wipe you out as much. When you do a high-intensity workout — running or cycling so hard that you can't carry on a conversation — you are so tired afterward that you tend to be lazier for the rest of the day. Instead of going shopping, you lie on the couch. People also tend to eat 20 percent to 25 percent more than normal because they're so hungry.

Don't you enter a fat-burning zone when you exercise at lower intensities? The idea of a fat-burning zone is b.s. In order to burn only fat, you would have to go at such a slow pace that you'd burn only two to three calories per minute. You'd have to walk 50 miles to get a decent workout. It's better to exercise at a moderate pace, so you'll burn some fat and some carbs. Doing that regularly can definitely help you control your weight.

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