New study suggests that fasted exercise might help with overall health and weight loss—but it’s important to do so responsibly. – By Selene Yeager
For decades, cyclists have sworn by fasted morning rides—rolling out the door after consuming nothing more than maybe some black coffee—as a way to fuel up their fat-burning metabolism and shed unwanted weight. Now, for the first time, a study confirms that exercise before eating may indeed do just that.
In the study, researchers from the University of Bath in the UK had a small group of overweight men perform 60 minutes of cardio on two separate occasions—once in the morning after a 12 hour fast and another two hours after eating a 650 calorie, carb-rich big breakfast, including cornflakes, toast, and OJ. They collected fat tissue samples immediately before and an hour after each session to check for changes.
The proof was in their genes—specifically two called PDK4 and HSL, both of which are triggered when your body uses stored fat to fuel your activity. When the men were fasted, the expression of these genes increased. When they exercised after eating, both decreased. That means you’re not just burning more fat during that bout, but also could enjoy long term fat-burning benefits, explained the corresponding author Dylan Thompson, PhD, in a media release, noting that when you exercise after eating, your fat tissue is too busy responding to that meal to fire up these fat burning changes. “Exercise in a fasted state might provoke more favorable changes in adipose tissue, and this could be beneficial for health in the long term,” he says.
Remember, we’re talking fat-burning—not performance. A couple of fasted rides a week can help with overall health and weight loss; but when you need to go hard, put a little fuel in the tank first.