Physical activity is generally insufficient by itself to bring about clinically significant weight loss.
You lose weight when your body is in negative calorie balance meaning that you eat fewer calories than your body needs. You can create a calorie deficit by:
For example, a 160 pound person who wanted to lose weight could skip the cola drink (12 ounces = 150 calories) or walk 36 minutes to burn off the same number of calories as the soft drink. The same person could also not have the large order of French fries (saving 540 calories) or walk for over two hours to burn off the same amount of calories. That’s a lot of walking! Who has the time???
This doesn’t mean that people who want to lose weight – or keep from gaining weight – should give up on exercise. Quite the contrary. First, regardless of weight status or weight outcomes, meeting the base recommendation for weekly physical activity (150 minutes of moderate activity, 75 minutes of vigorous activity, or a combination of the two) will yield significant health benefits.
If you want to prevent weight gain or perhaps lose a small amount of weight, the Advisory Committee report recommends doing 150-300 minutes of moderate-intensity a week. If you have lost a large amount of weight, then it is likely that you will need to do more than 300 minutes per week to keep the weight off. Of course, everyone’s body is different so you may be able to maintain your weight loss with less or more physical activity.
The bottom line? The best way to lose weight is to decrease calories eaten and increase calories burned in exercise. To keep the weight off, you will need to find the calorie balance that works best for you, but it will likely include a fair amount of physical activity. 1 Physical Activity Guidelines Advisory Committee. Physical Activity Guidelines Advisory Committee Report, 2008. Washington, DC: U.S. Department of Health and Human Services, 2008.