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Intermittent Fasting for Athletes: Can It Improve Performance?

6 Min Read

Intermittent fasting has exploded as a weight-loss trend. It’s become widely adopted by both celebrities and everyday dieters, and now it’s starting to garner attention in the academic world. Because of this attention, it’s important to unpack what intermittent fasting for athletes might entail. Their bodies require different – and often significantly more – nutritional intake, so it’s important to unpack how intermittent fasting might affect performance.

What is Intermittent Fasting?

Before adequate attention can be given to how intermittent fasting influences the performance of athletes, it’s helpful to understand the diet plan’s origins and functions.

The dietary sensation began in 2012 when the BBC’s Michael Mosely explored popular research being conducted about the health benefits of fasting. As he created his documentary, which required him to try the diet, he discovered that his overall cholesterol levels improved and that his “risk of contracting age-related diseases like cancer and diabetes” decreased dramatically. As a result, Britain and eventually the world would pick up the trend.

The specifics about intermittent fasting require a little more attention, though. A. Pawlowski of Today has unpacked the essentials for how intermittent fasting typically goes outside of the athletic world. She said the three most common intermittent fasting plans are the 16:8 diet, the alternate day fasting, and the 5:2 plan.

  • The 16:8 Diet: This form of intermittent fasting requires 16 solid hours of fasting every day. In the other eight hours, those looking to lose weight can eat practically whatever they want. Because they will finish their meals early in their waking hours, there will be more time for sugars and fats to metabolize throughout the day.
  • Alternate Day Fasting: Here, people fast every other day of the week. As they limit their calorie intake to 500 calories on their fasting day, they will be able to eat anything on the days they don’t fast.
  • The 5:2 Diet: In this model, dieters need to limit their consumption to 500 calories per day for two days in a row. In the other five days of the week, all other food is fair game.

While intermittent fasting requires stringent limitations on caloric intake, athletes can still exercise during their diets. According to K. Aleisha, M.S., CSCS, people can still exercise while fasting, but they need to be smart about it. Specifically, dieters need to follow four basic guidelines when exercising while fasting:

  • Commit to low-intensity cardio exercises during fasting times
  • Perform higher-intensity workouts after meals (or snacks during fasting days)
  • Consume protein-rich foods
  • Eat snacks to stabilize blood sugar

While this is a good starting point for understanding the relationship between intermittent fasting and exercise, most of this research has been completed on everyday dieters. As athletes are required to train for multiple hours practically each day, it’s important to zoom in on how the diet plan both benefits and potentially serves as a detriment for competitors.

Strategies for Athletes Considering Intermittent Fasting

Before the benefits of intermittent fasting for athletes can be given proper attention, it’s necessary to understand why they might choose this diet plan.

Before intermittent fasting reached its peak popularity, some athletes were already having to navigate the balance between fasting and training/competing. In the article “Optimizing training and competition during the month of Ramadan,” researchers looked into the challenges that Muslim athletes have to negotiate as they compete during the month-long fasting period. The researchers recommended ways that trainers and managers can help athletes prepare and perform during the period, maintaining that they apply a “holistic approach, rather than focusing on the single alterations/perturbations.”


To this end, the writers of the study cited the need for “variability among athletes and their specific needs (biological, psychological, cognitive-behavioral), and their social and living environment.” Trainers should work with athletes’ different body compositions in a one-on-one capacity.

Athletes who don’t observe Ramadan are beginning to consider fasting techniques for a variety of reasons. A 2017 scholarly article from the academic publication called The Journal of the International Society of Sports Nutrition focused on potential motivations and benefits of intermittent fasting for athletes. The researchers found that intermittent fasting would be immensely helpful for competitors aiming to lose fat, especially endurance athletes competing in sports like track and field, swimming, or cycling. Low-carbohydrate and intermittent fasting diets “can be similarly effective for improving body composition.” In order to achieve this goal while maintaining peak performance, though, athletes should consume more protein in their diets.

Additional research out of the journal Sports has highlighted the weight-loss and fat-burning qualities of intermittent fasting but warned that other behavioral changes should be considered. The researchers recommended that athletes looking to lose weight using an intermittent fasting diet should be careful about when and how they exercise, train, and compete, and they noted more research into their conclusion was needed.

What are the Side Effects of Intermittent Fasting?

Even though there’s still work still to be done on the research side, it’s helpful to consider the perspectives of athletes currently training. Craig Pickering is a former Olympic sprinter and bobsledder who now writes about nutrition in athletics. He wrote that, while there are marked benefits of intermittent fasting for athletes, competitors should be careful as they pursue the diet.

Specifically, he wrote that “not eating before a high-intensity exercise, such as sprints and resistance training, also will likely reduce training performance and, in turn, hamper competition performance.” Pickering also noted that an intermittent fasting plan for athletes may hinder or limit their overall protein intake. In the events that athletes compete while nutrient-deficient, there performances will suffer. As a result, he has recommended that athletes carefully plan when they eat to maximize performance.

Pickering’s sentiment is backed up by some recent research. An article in the academic journal Nutrition highlighted the importance of carbohydrate consumption for athletes training for competition. In most intermittent fasting plans, dieters cut out carb-rich foods to lower their calorie consumption on fast days. Carbs are important in an athlete’s diet, though, since they break down as energy to burn during training and competitive performances.

The study examined how a lot of existing research warns against athletes adopting a carb-restricted diet because they need enough energy to compete at the highest level. However, the study also made note of how little research is available at this time. In other words, intermittent fasting may still be appropriate for endurance athletes looking to drop weight, but more conclusive evidence is required.

As some researchers have gestured toward its benefits and others have rightly recommended caution, there’s still a considerable amount of work to be done to fully understand if the diet plan is suitable for athletic training. Professionals in the athletic and health industries will want to learn more about its nuances before recommending to clients. The ideal way to do so is through an online B.A. in Exercise Science. Concordia University, St. Paul’s flexible and fully online program prepares students looking to become athletic trainers, fitness trainers, and coaches to confront diet plans like intermittent fasting directly and soundly. At the same time, CSP prepares students to enter the research side of exercise science by equipping them with the tools to go on to conduct graduate-level study.

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