It’s an ongoing debate whether or not to eat before a workout. Some individuals need time to have a yogurt and a banana, while others roll out of bed and head out the door on an empty stomach. So which is the better for you: Eating a pre-workout meal or exercising fasted?
THE CASE FOR FASTED
A new study from the University of Bath in the U.K. found that not eating before a workout can burn more fat tissue. Researchers examined overweight males by having them walk for an hour at 60% of their maximum oxygen consumption on one occasion on an empty stomach, and then, on another occasion, two hours after enjoying a carb-heavy, high-calorie breakfast. They found that, after eating a meal, the subject’s bodies were focused on the meals and exercise didn’t have the same beneficial effect on fat tissue. “This means that exercise in a fasted state might provoke more favorable changes in adipose tissue, and this could be beneficial for health in the long term,” writes Dylan Thompson, in the study. Translation: More fat tissue was burned when participants exercised fasted.
“Most sports dietitians would not recommend a calorie-laden meal before exercise,” says Leslie Bonci, RD, founder of Active Eating Advice, nutrition consultant for the Toronto Blue Jays and Kansas City Chiefs. “Nevertheless, the theory that the body may be able to use more fat as an energy source in a fasted state is intriguing, as digestion is a non-factor in a fasted state.”
So it’s time to give up the pre-workout meal, right? Not necessarily. First, it’s worth noting that the study was only done on overweight men, so it’s hard to know how women would respond.
BUT IS IT FOR EVERYONE?
“My concern with working out fasted — contraindicated for those with diabetes, pregnant or lactating women and those who are hypoglycemic — is that this could also mean someone may not be optimally hydrated either, as food contains fluid,” says Bonci. “And while you may be burning fat, you may also be using muscle as an energy source as the body looks to fuel itself during exercise and it can more quickly break down muscle tissue to yield carbohydrates as an energy source than the time it takes to break down fat to free fatty acids.” Therefore, your muscle gains may be compromised along with fat, so you could burn into the results you’ve been working so hard to get.
This study also focused on fasted cardio versus a fasted strength workout. “I would doubt that the body would burn fat in a strength-training workout,” says Bonci. “The absence of fuel before a cardio workout is the potential for the body to use muscle as a fuel source in addition to fat. But fasting before a strength workout may have a catabolic or muscle breakdown effect, which is not what most people are looking for as a result of strength training.” And not eating protein before lifting may contribute to muscle protein breakdown.
TIPS FOR A PRE-WORKOUT SNACK
If you’re going to eat before a workout, it’s important to be aware of what you’re eating. A small banana, half a cup of oatmeal or a slice of whole-wheat toast with honey would suffice — but you shouldn’t be eating all three! The more food you have in your gut, the more blood is diverted to the stomach instead of the exercising muscles, explains Bonci.
The most important thing is to have a good, clean diet overall, to know your body and proceed accordingly with what works best for you, explains Adam Rosante, fitness and nutrition coach in New York City, author of Super Smoothie Revolution, whether that’s a fasted workout or eating prior to exercise.
“In terms of training fasted, the tricky part comes when a person can’t exert sufficient effort in a fasted state — and everyone is different,” he says. “I, for instance, do very well training hard, fasted — not because it burns more fat but because it works for me. But on the complete opposite end of that spectrum, I have clients who can barely function on an empty stomach, let alone train.”
While some individuals function fine fasted, others cannot focus as clearly, may fatigue faster and may be weaker with nothing in their stomach. In that case, their workout isn’t as good, which means they’re burning less fat. So the answer to the long-standing question about eating before a workout versus fasted exercise is that there still isn’t a definite answer. It’s about figuring out what works best for your body and sticking with that.