More fat? More carbs? What kind? How much? When?
Questions about what constitutes an ideal and practical diet for competitive athletes consume and confuse many athletes, as well as their coaches and families. But a new, comprehensive review about the science of sports nutrition published recently in Science provides a lucid overview of what currently is known — and not known — about how athletes should eat.
To find out more about these and other topics, I spoke with Louise Burke, a sports dietitian and professor at Australian Catholic University who has worked with many elite Australian sports teams. She wrote the new review with her husband John Hawley, the director of the Mary MacKillop Institute for Health Research at Australian Catholic University. What follows are edited and summarized excerpts from our conversation.
Q. In your review, you write that “carbohydrates are the predominant and critical substrate for working muscles” and that “the availability of carbohydrates, rather than fat, wins gold medals.” So athletes should be eating and drinking carbs?
A. Broadly speaking, if you had to stretch a big umbrella over the whole sports world and say, what dietary approach will bring the most performance benefits to the most types of athletes, then, yes, a high-carb diet would usually be the answer.
Q. In practical terms, how much carbohydrate are we talking about, especially during competition?
A. Based on what we know now, it looks like 30 to 60 grams of carbohydrates per hour during endurance events lasting several hours would be the sweet spot for most athletes. [For reference, a typical packet of a sports gel contains around 30 grams of carbohydrates, as does a banana or most single-serving bottles of sports drinks.]
Q. Some people, including me, might find it difficult to stomach so much food or drink during a race. Any advice?
A. Train your gut, just like you train your muscles. In the buildup to an event, practice with the foods or drinks you plan to have during the event, adding more, slowly. Some people find that combining multiple kinds of carbs, like glucose with fructose, are more tolerable than either one alone, probably because they are metabolized along slightly different pathways in the body. It’s also clear that you can swish sports drinks around in your mouth and spit without swallowing and your brain will interpret this as meaning you have more energy available. I think that’s fascinating and it can be useful, if you can’t stomach more carbs just then.
Q. The big controversy in sports nutrition right now seems to involve high-fat diets, which some people claim are better for performance than high-carb diets. Do we know whether one approach is really better for athletes?
A. [Dr. Burke noted that “the issue is so much more complicated than the Twitterverse would have people believe.” Carbohydrates remain muscles’ preferred fuel choice during exercise, she explained, because they can be metabolized so quickly. But our bodies contain much larger stores of fat than carbohydrates, so it makes intuitive sense that we might want to become better able to use that substantial fuel source, perhaps by eating a low-carbohydrate, high-fat diet.]
Q. But in the real world, do high-fat diets improve performance?
A. It depends on what kind of event someone competes in. In long, relatively low-intensity events like ultramarathons, fat might provide enough fuel. But even then, if someone wants to sprint at the end, they are going to need carbohydrates for that burst of exertion. For more intense events, there is evidence that high-fat diets impair performance. In our research with elite race walkers, we found that after they went on a high-fat diet, they could not train as hard and their competitive results suffered.
Q. So athletes shouldn’t try high-fat diets?
A. I wouldn’t say that at all. Some athletes love them. And we know that high-fat diets stimulate different molecular changes in the muscles than high-carb diets, some of which could be beneficial for performance.
[A practical compromise approach that allows competitors’ bodies to adjust to using both carbohydrates and fats efficiently, Dr. Burke continued, involves a technique called “train-high, sleep-low,” during which an athlete works out strenuously in the afternoon to deplete his or her body of carbohydrate stores, eats a high-fat, low-carbohydrate dinner, completes a long, slow workout in the morning, and then consumes a gloriously large, high-carbohydrate breakfast before training vigorously again. Dr. Burke threads this technique occasionally into her own training for marathons and other events, she says. ]
Q. What about protein?
A. That’s an interesting topic. We know that most athletes need more protein than the standard dietary allowances call for, to help in muscle repair. But we also are learning, by studying athletes, how important sufficient protein is likely to be for nonathletes, especially older people, if they want to maintain muscle mass.
Q. With all the emerging science about nutrition and sports, what overall advice would you give a recreational athlete about how to eat?
A. Talk to a sports dietitian. I think many recreational athletes get caught up in trends and forget the basics. If you are an Olympic athlete, then, yes, the minutiae of your diet’s composition and timing are very consequential. The rest of us should concentrate on simple, healthy eating.
