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  • Writer's pictureHaley Schlechter, RD, LDN

Fat Fever: Fat and Athletes

We have now covered carbohydrates and proteins for athletes and to this point should be pretty clear on the importance of both as macronutrients in our daily lives. Up next, fat the stuff that makes up every cell wall in our body, keeps our skin tough, and regulates inflammatory hormones! Fat is the last of the macronutrient in our base training before we move on to things like the wonderful world of supplements and weight management issues, so let’s get started.

Fat and Athletes:

There is a lot of talk in social media currently about the magic of super high fat diets. The truth is, high fat diets, for athletes especially, are not only unsustainable but not beneficial. About 20-30% of your diet should be made up of fats. By increasing fats much over this recommendation you sacrifice precious carbohydrates (which we know to be our bodies number 1 fuel source) and protein (how we rebuild and maintain muscle mass). Yes, our bodies can adapt to this sort of diet over time, but research has shown that performance is often sacrificed. This is because fat cannot be put to use as quickly as the other macronutrients.

How Fats Are Used: Some Science

Fat, alongside carbohydrates, are being used all day as an energy mixture in our bodies but they are used in different ratios depending on need. During our most sedentary times, fat is being used as your main energy source because there is no need for quick energy. At the onset of exercise, along with carbohydrates, fat is put into use more, but at a slower rate than carbohydrates. This happens because you need quicker energy which carbohydrates provide. How much fat an athlete will utilize as exercise continues depends on intensity, duration, how well adapted the athlete is and their diet. As intensity increases fat utilization goes down due to higher demand of quick energy. As duration increases though, your stores of carbohydrates begin to run low and your body adapts by raising its use of fat to a higher level.

Endurance Athletes:

A well trained endurance athlete has the ability over time to adapt to using more fat during longer duration exercise then an untrained endurance athlete, but once they reach a VO2 max of over 75% their body adapts to its increased need of immediate energy and carbohydrates are used almost entirely. Fat need for endurance athletes is around 30% of total calories.

Strength Athletes:

For the most part, strength based athletes are going to be doing short duration high intensity exercises throughout a practice, so they are going to be burning mostly carbohydrates during their training (VO2 max being over 75% more often than endurance athletes) These athletes still have the ability to adapt and burn more fat during exercise than untrained athletes though, just not at the same rate as an endurance athlete. Like endurance athletes, fat needs for strength athletes is around 30% of their total calorie intake for the day.

Summary Points:

  • Athletes need fat to rebuild cells they are breaking down during exercise and regulate inflammation

  • Increase Intensity: you need energy and you need it now= CARB utilization higher

  • Increase duration: glycogen (CARBS) are running low= FAT utilization higher

  • Overall: longer duration moderate intensity exercise utilizes fat at higher rate than high intensity shorter exercise.

  • Trained athletes are able to burn fat at higher rate than untrained individuals

Ketogenic dieting for athletes? Topic to be discussed in great depth soon!


  1. Jeukendrup, Asker E., and Michael Gleeson. Sport Nutrition: An Introduction to Energy Production and Performance. Champaign, IL: Human Kinetics, 2010. Print.

  2. Kiens, Bente, and Jørn W. Helge. "Effect of high-fat diets on exercise performance." Proceedings of the Nutrition Society 57.01 (1998): 73-75.

  3. Helge, Jørn W., B. O. L. E. T. T. E. Wulff, and Bente Kiens. "Impact of a fat-rich diet on endurance in man: role of the dietary period." Medicine and Science in Sports and Exercise 30.3 (1998): 456-461.

  4. Yeo, Wee Kian, et al. "Fat adaptation in well-trained athletes: effects on cell metabolism." Applied Physiology, Nutrition, and Metabolism 36.1 (2011): 12-22.

  5. Burke, LOUISE M., and JOHN A. Hawley. "Effects of short-term fat adaptation on metabolism and performance of prolonged exercise." Medicine and science in sports and exercise 34.9 (2002): 1492-1498.

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