Fad Diets for Athletes

Author: Annika Weisjahn

There are new diets and trends that seem to come up every year. While fad diets may be very popular and relatively harmless to the regular population, there may be more things to consider when looking at these diets through the eyes of an athlete. These diet plans often need modification to make sure that they are meeting their energy needs, macronutrient, and micronutrient intakes are met to fuel their training and performance goals. (1) A popular trend in these diets is to restrict carbohydrate intake; however, it is also shown that impaired physical performance can also be attributed to a low carbohydrate diet (2). Most people working in the exercise science field will say carbohydrates must make up the better part of an athletes diet if they want to perform at their peak level (2). This is important because in order to fuel muscles in a high intensity workout, they need glycogen in which they get from carbohydrates. However, it is not just carbohydrates that are important to fueling a workout; if you are working out for longer than a few minutes, a workout is fueled by a combination of intra-muscular and extra-muscular carbohydrates, lipids, and a small amount of amino acids (3).

One diet that is very popular right now is the Ketogenic Diet. The keto diet consists of consuming less than 50g of carbohydrates per day and at least 75% of the calories from fat (3). In addition to the low carbohydrate and high fat diet, people may also consume a moderate amount of protein. The thought behind this diet is that it is an attempt to increase fat oxidation during exercise, this will in turn slow the oxidation of the limited carbohydrate stores and sustain near-maximal performance through increased carbohydrate availability, stemming from less oxidation at submaximal intensities (3). However, it is also shown that even though there is an increase in fat oxidation, there is no clear data that shows it improves performance (3). There are some data that shows that it can be very effective for weight loss. If an athlete is looking to lose weight this may be a potentially effective diet but should know it will not directly affect their performance.

The Paleo diet is another diet that is trending at the moment. When on the Paleo diet, a person does not eat any starches (such as potato, corn, refined cereal), grains (such as pasta, rice, bread, flour, barley), processed foods, added sugar, or dairy products (5). Even though the number of carbohydrates is not necessarily restricted, the type (which can have a large impact on glycogen stores) the draw backs of this could be very similar to that of the Keto diet with carbohydrate restriction which could inhibit necessary glycogen to fuel the muscles. Some positives to this diet can include positive effects on the metabolic markers but, like the Keto diet, there is little evidence supporting actual improvements in physical performance for the athletic population (6)

Intermittent fasting is a little different than the other two fad diets we have talked about. Intermittent fasting can take many different forms but the most common is the 16:8 diet, this consists of 16 hours of fasting every day, and normal eating in the remaining 8 hours. There has been some data that has shown it can reduce the rate of type two diabetes which could be helpful to an athlete looking to lose fat (4). However, there are many draw back to this diet, like mentioned before, an athlete needs to be able to properly fuel their workouts. If they are fasting before a performance or training session, they could run the risk of seriously decreasing their performance. It has been suggested that if an athlete wants to take part in a workout like this they should commit to very low intensity while fasting and perform their higher intensity workouts after meals or snacks as you need the fuels from your food to sustain your workouts (4).

In conclusion, an athlete needs to be very careful if they were to consider participating in one of these fad diets. It is critical they that consume the energy they need to fuel their workout, most of which comes from eating carbohydrates which contributes to glycogen stores. The Paleo and Keto diets are two of those that heavily restrict your carbohydrate intake, while intermittent fasting does not, it is very restrictive on the time period that you can eating in general in which you run the risk of not consuming enough energy, and must be careful you are not exercising heavily during your fasting periods. There can be small positive to these diets if athletes are looking to lose weight, but they must understand that the diets have not been shown to directly improve performance. So, are these fad diets good for athletes? There is no clear answer, however, most experts will say that the best thing an athlete can do is eat a diet balanced with all food groups and adequate amounts of fluid (8).


  1. Rosenbloom, C. Popular Diets and Athletes: Premises, Promises, Pros, and Pitfalls of
    Diets and What Athletes Should Know About Diets and Sports Performance, Nutrition
    Today:September/October2014-Volume 49-Issue 5-p244-248.
    doi: 10.1097/NT.0000000000000043
  2. Phinney, S.D. Ketogenic diets and physical performance. Nutr Metab (Lond) 1, 2 (2004).
  3. McSwiney, Fionn T et al. “Impact Of Ketogenic Diet On Athletes: Current Insights.” Open
    access journal of sports medicine vol. 10 171-183. 15 Nov. 2019,
  4. “Intermittent Fasting for Athletes: Can It Improve Performance?: CSP Online.” Concordia
    University, St. Paul Online, 6 Feb. 2020,online.csp.edu/blog/intermittent-fasting-for-
  5. Medicine, National Academy of Sports. “The Paleo Diet for Strength/Power
    Athletes.” NASM, blog.nasm.org/paleo-diet-for-strength-power-athletes.
  6. Escobar, Kurt A et al. “The Effect of a Moderately Low and High Carbohydrate Intake on
    Crossfit Performance.” International journal of exercise science vol. 9,3 460-470. 1 Oct.
  7. McSwiney, F. T., Doyle, L., Plews, D. J., & Zinn, C. (2019). Impact of ketogenic diet on
    athletes: Current insights. Open Access Journal of Sports Medicine, 10, 171–183.
  8. University of Wisconsin Hospitals and Clinics Authority. “Eating for Peak Athletic
    Performance.” UW Health, www.uwhealth.org/health-wellness/eating-for-peak-