Is it better to eat before or after exercise?

ATLANTA - We work hard when we work out, so how do we get the most bang for our exercise buck?

Is it better to fuel up beforehand, or wait and eat after we're done?

Emory internist Dr. Sharon Bergquist said a lot of it has to do with personal preference.

"Some people like to exercise on an empty stomach because they find that a hard workout upsets their stomach," Bergquist said. "Some people just find they hit that wall, and they can't get past that wall."

If you're trying to lose weight, some experts argue a fasting workout, or sweating it out on an empty stomach, is the best way to burn fat. The reason is the way our brains burn fuel.

"So the primary fuel for the brain is glucose," Dr. Bergquist explained. "So, if your brain is low, it's going to go to any source in the body, be it fat or muscle, and it's going to try to turn that into fuel, turn that into glucose."

So, if you work out on an empty stomach, say first thing in the morning, the thinking goes your body will burn stored fat for energy. And Dr. Bergquist said that might work, for a little while.

"However, the body is constantly dynamically alternating its sources of fuel that we use as energy," she said. "And, what we see is that, if you looked at what happens not over the course of an hour, but over the course of a day or two, the compensation for that by burning carbohydrates later in the day."

Meaning, you may burn fat -- for a little while, before your body switches gears.

"So, longer-term, body composition doesn't change much by whether you eat before or after exercise," Dr. Bergquist said. "It's only a short-term effect around the time of exercise."

The bottom line, Bergquist said, is fuel your work out whatever way works best for you.

And remember to drink plenty of fluid, especially when you're sweating it out in the Georgia heat.