What’s Better for Athletic Performance: Carbs or Fat?


We all know adequate nutrition is a big component of athletic performance, particularly for the serious athlete. When it comes to fueling for things like endurance races or high-intensity sports, carbohydrates have long been the primary fuel source of choice. Recently, however, some professional athletes have made headlines for, quite literally, going against the grain––trading carbohydrates for fat to fuel everything from 50-mile runs to cross-court sprints. Not surprisingly, this has many sports-minded individuals wondering just what is better for performance, carbohydrates or fat.

How Carbohydrates Compare to Fat During Exercise
While the body can store both carbohydrates and fat, when it comes to converting these nutrients into energy, carbohydrates are by far the fastest and most efficient form, which is why they’re great for fueling athletic performance.

Fat, on the other hand, is a slower-burning fuel. As duration increases and/or intensity decreases, the utilization of fat as an energy source increases at the cost of speed and intensity.

The body’s fat stores are almost limitless in relation to available carbohydrate stores. This makes fat an attractive fuel choice for endurance exercise like long-distance runs, bike rides and swims. How well your body can use fat during exercise depends on how athletically conditioned you are.

Can Fat Adaptation Improve Performance?
It’s been well established that, with training, the body becomes better at using fat for fuel, and in 2004, the Australian Institute of Sport concluded that even in the short term, the body can adapt to a high-fat, low-carbohydrate diet by burning more fat during exercise.

However, according to Louise Burke, researcher and head of sports nutrition at the Australian Sports Commission, research hasn’t yet shown that extremely high-fat, low-carbohydrate diets (also known as ketogenic diets) actually enhance sports performance.

In fact, these studies generally show that high-fat diets impede athletic performance during high-intensity exercise such as sprints, and lead to an increase in perceived exertion, meaning those sprints felt harder. It seems, in these circumstances, nothing beats those fast-burning carbohydrate stores for fuel.

To date, the vast majority of studies looking at fat adaptation and performance are small in size and lack consistency in defining these “high-fat” and “low-carb” diets, weakening both sides of the argument for and against fat-adapted training. It also makes the findings less actionable to the average person looking to tweak their diet to improve performance. More research is needed in larger, more diverse populations before the final verdict on fat adaptation, and whether or not it can improve or even sustain one’s performance, is reached.

It is best to stick with the sports-nutrition strategy that is evidenced-based, which is adequate nutrition from carbohydrates, protein and fat, keeping in mind your needs are dependent on type of sport, sex and environmental conditions. Inadequate nutrition can result in muscle loss, increased fatigue and prolonged recovery, making you more susceptible to injury and illness.

Fueling with Carbohydrates or Fat: What Is the Best Strategy?
If you’re looking to optimize your performance, it’s wise to stick with the sports-nutrition strategies that have been consistently backed by research. Carbohydrates are converted into energy by muscles faster and more efficiently than fat, proving why they’ve been the go-to fuel of choice for so many athletes for so long now.

Every sports-nutrition plan should be individualized, however, as one person will respond differently than others. For this reason, you may want to experiment with different carb-to-fat ratios and see how it impacts your performance and overall health. Whether you’re a recreational or serious athlete, a sports dietitian can help tailor a nutrition plan to meet your individual needs.

One last thing to keep in mind: If you’re an athlete or someone who is concerned with performance, when you eat your calories is just as important as what and how many calories. Not eating enough or eating a low-quality diet can result in muscle loss, increased fatigue and prolonged recovery. As far as timing goes, the important windows for thinking about fueling for performance are: 3–4 days, 24 hours and 4 hours before training or competition. Additionally, spreading your caloric intake throughout the day is ideal to help maintain lean body mass, reduce body fat and have the energy you need to get through your training session and competition well fueled.


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