A:Why is everyone so wishy washy on this subject? It all comes down to burning fat. Some researchers have claimed that exercising in a fasted state (i.e. right after you wake up) helps train your body to burn fat more effectively, while others say that’s simply not true.
If you were to search Outside, you would probably notice that we’ve also published conflicting information on whether or not to eat before your morning training session. Recently, Selene Yeager recommended spinning before breakfast to “burn fat better,” while in the past, our nutrition experts have said that doing exactly that is buying into a “nutrition myth.”
Unfortunately, the debate is not over, so there’s no definitive scientific answer. But research suggests that athletes with weight loss goals, like yourself, should probably eat something before training.
The study most often cited in articles that recommend exercising in a fasted state was published in the Journal of Applied Physiology in 2010. After the study appeared, everyone from the New York Times to Men’s Fitness touted exercising before breakfast as the fastest way to weight loss. The problem with that study, says Lauren Antonucci, a marathoner, sports dietician, and owner of New York-based Nutrition Energy, is that it wasn’t meant for athletes.
“This study was done on a hypercaloric, high-fat diet,” Antonucci says. “It was looking at whether or not people who are eating 50 percent of their calories in fat should exercise in a fasted state. How many athletes actually fall into that category? Most athletes concerned with their fueling and performance are not eating 50 percent of their calories in fat and are not eating 30 percent more calories per day than their bodies need.”
For people who are eating too much all of the time, yes, she says, they can benefit from exercising in a fasted state. But for athletes who want to lose five or 10 or 20 pounds, and who are already in training, “you’re better off fueling first,” Antonucci says. “The carbohydrates and calories you take in will help you maximize your energy and workout, prevent hunger later, and help you achieve your weight loss goals.”
She recommends eating some carbs before working out whether your goal is downsizing or performance or both, even if that something is as simple as a banana or a few handfuls of cereal. If you’re exercising very early in the morning and can’t eat, she recommends sipping on a carbohydrate drink like Gatorade.
Can you get up and work out for 45 to 60 minutes without eating? Yes, says Antonucci, but if you find yourself dizzy or hungry, eat something. “It’s better to have some carbs on board so you can enjoy your workout, which will be better for long-term compliance, weight loss, and success,” Antonucci says.
For every study like the one cited above, there are a handful of others that have posted different outcomes. A study published in 2011 in the International Journal of Sport Nutrition and Exercise Metabolism found that fasting before performing moderate exercise (subjects performed 36 minutes of cardiovascular training on a treadmill at 65 percent of their maximum heart rate) did not improve fat metabolism. Those researchers recommended eating a light meal before exercising.
And as for weight loss in general, a study published in June 2012 in the journal Appetite found that it was no more effective to run for 60 minutes on a treadmill before eating breakfast than after to aid weight loss.
THE BOTTOM LINE: If you're in training, you're probably better off eating something before exercising, even if it’s only a banana or some Gatorade.