Sunny Blende, a sports nutritionist, once described ultramarathons as “eating and drinking contests, with a little exercise and scenery thrown in.”
Marathons, too, have come to resemble mobile buffets, with fueling stations almost every mile. And top cyclists and triathletes are now scarfing down more sugary drinks and gels than ever in search of a performance edge. It’s enough to make some casual athletes wonder whether they should pack some calories every time they lace up their trainers or head to the gym.
This growing focus on mid-exercise refueling is based in part on research showing that elite athletes can digest calories more rapidly than previously thought. But whether the rest of us should emulate this approach is less clear, according to running coach and sports nutritionist Matt Fitzgerald. In fact, he said, “the topic raises fundamental questions about the purpose of fueling in training.”
Before you rethink your workout nutrition plan, Mr. Fitzgerald and other experts recommend considering three key variables: how long you’re exercising, how hard you’re pushing and what your goals are.
How long is your workout?
The case for refueling during a multihour effort like a marathon is straightforward. Your body can store only a limited amount of carbohydrates, the fuel of choice for hard exercise. After 90 to 120 minutes, unless you replenish your body’s stores of carbs, your muscles will shift to using forms of fuel that aren’t as easily metabolized, such as fat. That causes the heavy-legged and lightheaded feeling endurance athletes refer to as “bonking,” or hitting the wall.
Even for efforts shorter than 90 minutes, extra carbs can be helpful. Unlike a car that can drive at full speed until it runs out of gas, your muscles start working less efficiently even when they’re halfway fueled, said Tom Shaw, a performance nutritionist who has worked with professional soccer clubs in Europe and the Middle East.
Current sports nutrition guidelines suggest that athletes don’t need to refuel during efforts lasting less than 30 minutes. It’s also clear that they require progressively more aggressive refueling during multi-hour efforts.
But there’s a middle ground between about 30 and 75 minutes where the guidance is more ambiguous. You might get a boost from swallowing a few sips of a sports drink, the guidelines say — or even, studies have found, from swishing the drink in your mouth and spitting it out. In other words, the benefits during these relatively short workouts may be less about fueling the muscles than about tricking the brain into thinking that more fuel is on the way.
How hard are you pushing?
The guidelines above assume that you’re pushing as hard as you can, as you would during a race or a soccer match. During less intense exercise, on the other hand, your muscles burn fewer calories and can rely more on stored fat — a fuel source that is effectively unlimited, even in the fittest athletes.
As a result, even the professional soccer players Mr. Shaw works with generally don’t need to refuel during practices lasting up to 90 minutes, since they’ll have all the energy they need from their preworkout meal. “If a player needs a gel during a typical training session, it usually means they didn’t prepare properly,” he said.
“For the average person training for health, fueling during a 45-minute gym session isn’t necessary,” he added. “A light, easily digestible snack beforehand — like a banana or a lean chicken sandwich — will do the job.”
What’s the goal of your training session?
In a competition, it makes sense to do anything that might improve your performance by a percentage point or two. In a workout, that’s not necessarily true. “Are you eating for performance or for overall health?” asked Barry Braun, a professor of health and exercise science at Colorado State University. “Because you make some different choices depending on the primary goal.”
In the early 2000s, Dr. Braun and his colleagues published a series of studies that confirmed that exercise has immediate benefits for blood-sugar control and other health markers, but that these benefits diminish if you immediately replace the calories you burned during the workout.
Other researchers have found similar trade-offs when comparing training for endurance sports on a full or an empty stomach, suggesting that depleting your energy stores is one of the signals that tell your body to adapt and get fitter. The upshot is that staying fully fueled when you don’t really need to may mean you’re not maximizing the benefit of the workout, Dr. Braun said.
There’s another reason to think twice about fueling overzealously during shorter or less intense workouts, according to Mr. Fitzgerald. Many of the calories athletes take in during training come in the form of sugary gels or sports drinks, which may have negative health effects in the long term.
There’s no clear benefit to fueling easy workouts, so you might as well err on the side of caution and avoid the extra sugar, he said.
Still, Mr. Fitzgerald’s view is that the overwhelming majority of runners don’t take in enough calories during their training. Of the roughly 200 people who have attended his running camps over the past few years, he said, perhaps 10 were already fueling their training appropriately before they arrived. He doesn’t tell his athletes to fuel during shorter, easier runs, but he strongly encourages them to eat or drink during any run that’s long or hard enough to generate “significant fatigue.”
If they can get in this habit, he said, “they will feel better, perform better, recover better and, ultimately, race better.”
Alex Hutchinson is a columnist at Outside and the author of “The Explorer’s Gene: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map.”
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