The Science of Weight Loss

The science behind weight loss is actually quite simple. If you want to lose weight, you have to use up more calories than you eat.

On paper, losing weight is simple math. One pound of fat equals about 3,500 calories. If your goal is to lose one pound of fat, your body has to burn off 3,500 calories. If you cut back your caloric intake and/or increase exercise each day to create a deficit of 500 calories, you can lose one pound every seven days.

In real life, however, it's more complex. Studies show that losing weight and keeping it off requires that you permanently change the way you think about food and dieting and make lifestyle changes to improve your overall health.

What works

Weight loss isn't just going on a "diet," and it isn't about extremes. What really works is making healthy lifestyle changes. Your goal of losing weight shouldn't be a temporary one—you want to get fit and healthy for life. To do that, you have to adopt a lifestyle that you will follow for a lifetime.

Adjust your daily diet so that it includes:

• Plenty of fruits and vegetables

• Whole grains instead of refined white flour

• Lean proteins, including fish, beans, and skinless poultry

• Fat-free and low-fat dairy

Set some limits for better health without feeling deprived:

• Have dessert in moderation.

• Drink alcohol only in moderation.

• Avoid too much of any kind of fat, but in particular the unhealthy saturated and trans fats.

• Limit sugar.

• Limit salt.

It's also important to eat regularly throughout the day—no starvation and no skipping meals. You can divide your food intake into three meals and a snack or eat as many as six small meals over the course of each day.

You also need regular exercise both for losing weight and for maintaining your goal weight once you've achieved it. One study found that 44 percent of dieters tended to eat less after exercising. To lose weight, you'll need to exercise at a moderate pace for about 60 to 90 minutes on almost every day of the week.

What doesn't work

Fad diets might sound tempting, but they don't create lasting results. Even if you do lose some weight, it's likely that the minute you return to your previous eating habits, you'll gain that weight right back—and possibly even more. Dieting and severe calorie restrictions aren't effective in the long term. The more you deprive yourself, the more likely you are to binge on desserts, potato chips, and other junk food.

Taking diet pills is also unlikely to work long-term. Again, even if you do lose some weight when you first start taking these medications, any pounds you lose are often regained. Also, diet pills may cause side effects. Taking diet pills is just another temporary solution to a weight problem and doesn't encourage you to make healthy changes in your diet and lifestyle.

For long-lasting results, set realistic weight-loss goals. You should aim to lose between one and two pounds per week for effective weight loss that lasts. Any more than that, and you're at risk of losing water and healthy muscle rather than fat.