Exercise on Empty to Burn Fat, Study Says

Athletes load up on carbs before exercising in order to fuel their muscles, but if your aim is to burn fat then you should consider working out on an empty stomach, according to the findings from a new study.

The Associated Press reported June 4 that European researchers found that cyclists who fasted before they trained burned more fat than those who ate. “When you exercise (after fasting), your adrenalin is high and your insulin is low,” explained researcher Peter Hespel of the University of Leuven in Belgium. “That ratio is favorable for your muscles to oxidize (break down) more fatty acids.”

Hespel said that skipping breakfast is the best way to get a fat-burning workout, since you’ll need to avoid eating carbohydrates for six hours in order to get the body to burn fat, instead. “Science is finally catching up with what smart runners have always known,” said Ron Maughan, a sports medicine expert at Loughborough University in Britain. “If you have a long, hard run without breakfast once a week, that hard run will train you to burn fat. And for the rest of the week, have plenty of carbohydrates so you can train hard.”

A fasting workout could help people with diabetes, Hespel said. However, other researchers said that exercising without eating would mostly burn fat stored within muscle, not elsewhere in the body, making the effect on the waistline minimal unless you were doing an intense workout. Some experts recommend eating at least something small, like a banana, to keep your blood sugar up.

The research was published in the April 2010 issue of the journal Medicine & Science in Sports & Exercise.