Ask the Personal Trainer: Low- vs. High-Impact Fat-Burning

In our weekly fitness Q&A series, William Sukala, MS, CSCS, answers questions about fitness, from whether to eat before exercising to how to treat sore muscles.

Q: I have read that low-impact exercise burns more fat than high-impact exercise does. How can this be?

A: Exercisers continue to argue over which is better for fat burning. So this offers a perfect opportunity to look at the science behind the debate. Ultimately, both low- and high-impact exercises burn fat. But in the big fat-loss game, it's how many calories you burn off, relative to how many you take in, that makes the difference. Let's take a closer look.

It is true that low-impact exercise burns more fat than does its more intense high-impact cousin. But not so fast: There's more to it than meets the eye. Low-impact, slower-paced exercise burns proportionally more fat than carbohydrate as a fuel source. But the trade-off is that you also burn fewer overall calories per unit time you exercise.

On the other hand, high-intensity exercise burns proportionally more carbohydrate than fat, but in the bargain, you burn more calories overall. This translates to larger calorie deficits, which are later "paid back" with stored body fat.

Low-impact exercise is still a very effective way to lose body fat. You just need to go a little longer in order to burn more calories. As you improve your fitness level, you'll be able to tolerate a faster pace for longer. No matter which you do, remember that consistency is the key to success — and that if you burn up more calories than you take in each day, you'll lose body fat.

In this Q&A series, William Sukala, MS, CSCS, answers questions about fitness and exercise. Read more articles from our personal trainer.