How Fast Can Crunches Help to Lose Weight?

Like any form of exercise, crunches can help you lose weight. Doing crunches or sit-ups expends energy, which has a direct impact on calories burned. Obviously, the more energy you expend, the more calories you can burn, helping you to lose excess weight. But if you’re doing crunches just to lose belly fat, you may not see the results you expect.

Crunching Calories

The number of calories burned doing crunches is largely based on your weight and level of intensity. If you weigh 155 lbs. and do crunches at a moderate intensity, you can expect to burn roughly 10 calories per minute. As you get further into your repetitions, you’ll likely begin to slow down your intensity, so, after 10 minutes, you may burn around 99 calories, give or take a calorie or two. At about 20 minutes, which would be difficult to maintain, you could see a caloric burn of almost 200 calories.

Caloric Deficit

Weight loss happens when you generate a caloric deficit. According to estimates by the National Institutes of Health, a pound of fat contains about 3,500 calories. Creating a deficit of this amount should then cause a weight loss of 1 pound. Looking at the amount of calories burned doing crunches for 10 minutes each day, you can expect to lose a pound of fat every 35 days if you currently weigh 155 pounds -- not a particularly impressive amount, but you would develop a powerful core.

Weight Loss

If you’re looking to lose more significant amounts of weight, you’re much better served using another form of exercise as well as making changes to your diet. Jogging, biking, swimming and kayaking are all activities much easier to sustain for longer periods of time, thereby increasing the amount of calories burned at each exercise session. A 155-pound person biking at a moderate intensity for 30 minutes burns 260 calories. Increasing the intensity to vigorous boosts energy expenditure and burns almost 400 calories in half an hour. That translates into a weight loss of 1 pound every two weeks or nine days, respectively. Combine this cutting calories by 250 a day, and you can expect to lose 1 pound every week or five days.

Burning Belly Fat

Though you’re working the abdominal muscles with crunches, this form of exercise doesn’t spot-burn belly fat, says Colleen Doyle, director of nutrition and physical activity for the American Cancer Society. You really need to look at broader activities as well as dietary change to encourage the caloric deficit needed to lose excess weight around your middle.