Why is my friend's low carb diet working for her, while my healthy diet isn't working for me?

Q: My friend went on a low carb diet, did absolutely no exercise and has lost 20 pounds in four months. I watch both my bad and good carbs, and I walk three to four days a week, but I haven't lost any weight. Why not?

Low carb diet versus healthy diets with good carbs: here's the difference.

A: People tend to lose weight quickly on low carb diets because they restrict their calories to about 1,200 a day. "It's not the 'miracle' of eating protein or not eating carbs," says Cindy Moore, M.S., R.D., director of nutritional therapy at the Cleveland Clinic Foundation in Indiana.

Chances are, you're consuming more calories than your friend is. But that's good. Most people who go on restrictive diets eventually regain the weight. (In healthy diets, physically active women generally need at least 1,800-2,000 calories a day.) "A diet is an artificial way of eating," Moore says. Once they go off the plan, people usually resume old eating habits and regain the weight.

Losing weight without exercising is not an effective strategy. You tend to lose muscle along with fat, so your metabolism slows down. To help you lose weight, add two days a week of strength training to boost your metabolism or at least preserve your muscle mass as you lose weight. To burn extra calories, add an extra day or two of walking to your current program.

On the nutrition front, there's no benefit to "watching your good carbs" -- unless the carbs are nutritionally void, high-sugar foods such as sodas, cookies and cakes, and processed snacks. Good carbs such as whole grains, fruits and vegetables, and legumes are important for maintaining good health and fueling exercise, and they should make up at least 50 percent of your total calories in healthy diets. Rather than making drastic changes to your diet, make small modifications that you can sustain healthy eating indefinitely.