How Body Fat Affects Athletic Performance


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If you’ve ever wondered how your body fat percentage affects athletic performance from running to jumping, you are not alone. This article will open your eyes to what could be the fastest way to improve your athletic performance…and your coach probably has no idea.

After following the advice presented below, you will be able to:

  • Run Faster
  • Jump Higher
  • Improve Quickness & Agility
  • Increase Power
  • … without ever going for a run, or even playing a sport.

    Prepare to be enlightened my friend!

    How Body Fat Affects Athletic Performance | The Origin

    This past weekend I was at the Arnold Sports Fitness Festival where I attended a lecture by exercise professor and coach Dr. Todd Miller entitled:

    “From Overfed to Thoroughbred: Training and Dietary Strategies
    for the In-Season Power Athlete”

    As I was waiting for his presentation to begin, I thought Dr. Miller was going to discuss a bunch of training and diet strategies I’ve read about many times. It turns out I was dead wrong.

    Dr. Todd began his presentation describing his quest to learn how athletic performance can be maintained for the in-season power athlete. When he became a Strength Coach at Penn State several years ago, Dr. Todd learned of an untapped treasure trove of information on Penn State athletes that had never been analyzed before. This information, which spanned all Varsity sports teams from men’s football to women’s soccer featured strength stats throughout the year on every athlete.

    Dr. Todd took it upon himself to analyze the data, which he later published in a research paper. As expected, he noticed that athletic performance tended to decrease throughout the season as players decreased overall training volume and increased sports-specific preparation for competitions.

    On further review, Dr. Todd noticed that one team in particular – the women’s soccer team – experienced significantly decreased performance in-season relative to the other teams. He also noticed that while the average weight of the female soccer players stayed roughly the same from pre to post-season (136lb vs. 134lb respectively), body fat increased 3% translating into 6 pounds of muscle loss and 4 pounds of fat gain.

    Immediately after reviewing this information, Dr. Todd formulated a questions that would guide the rest of his presentation – “How do changes in body composition affect athletic performance?”.

    How Body Fat Affects Athletic Performance | The Insight

    After exhaustive research, Dr. Todd could not find any academic papers that answered his simple and important question of how body composition affects athletic performance.

    He did learn, however, that the horse racing community understood how adding weight to a horse would affect the horse’s running speed. In fact, horse racers had it down to a science.

    A race horse is an amazing physical specimen that typically weighs 1300 pounds at around 5-6% body fat and can run up to 45 mph.

    With this in mind, see if you can answer the following question:

    How much weight do you need to add to a horse to slow it down?

    Yes, a horse is a 1300lb animal, but…

    If you guessed 200lb, you would be wrong.

    If you guessed 50lb, you would be wrong again.

    What about 30lb? Nope, that’s not right either…

    The answer is 2-5lb is all the extra weight needed to slow down a horse so that it loses a race. In fact, only 2lb extra will slow down a horse roughly 8 feet, or one horse length.

    How Body Fat Affects Athletic Performance | The Analysis

    After learning this intriguing information about race horses, Dr. Todd reasoned even gaining a few pounds of fat for an athlete could have significant performance implications. He decided to put his reasoning to the test by loading 170lb athletes with 3.4lb (or 2% body fat) and having them complete power related tests, which he published in a research paper.

    Here’s a quick snapshot of the results:

    For a 170 lb. athlete, a fat gain of 3.4 lbs. (2%), could result in a vertical jump height loss of 2”, and a 40 yard dash time increase of 0.26 seconds. If you are not familiar with the 40 yard dash, 0.26 seconds is an eternity. This is the same sprint test all NFL football players must do at the NFL Combine, which tests the athletic ability of all the athletes before entering the league. A 0.1 second difference can mean millions of dollars.

    Going back to those Penn State female soccer players, recall that there was a 4lb increase in fat (2.9% of body mass) and a 6lb loss in muscle (4.4% of body mass). We’re talking MAJOR decrease in performance.

    How Body Fat Affects Athletic Performance | The Conclusion

    What happens if you are a triathlete, or competitive runner with 20% body fat and a good 10-20lb of fat to lose?

    Well you are essentially carrying the equivalent of a 10-20lb dumbbell with you at all times, which is going to have a massive impact on your athletic performance, let alone your joints. One could make the argument that losing the excess fat (without losing muscle of course) would help performance more than logging extra miles.

    What about increasing weight by adding muscle mass. Does that hurt performance?

    The short answer is no, adding muscle typically helps athletic performance. The power/weight ratio, which is meticulously measured by the cycling community is improved when muscle is gained. The power derived from 2lb of muscle will more than offset the detriment of adding the 2lb of weight. In some cases, because of aerodynamics, losing overall body mass (muscle mass and fat) can sometimes help a cyclist go faster, but this has not been proven with sprinters and other power related athletes.

    What are the key takeaways about increasing athletic performance so you can run faster, jump higher, improve quickness, and also power in a relatively short period of time? The first and most important is…

    => Lose Fat Without Losing Muscle! <=

    Here’s the last slide of Dr. Millers’ presentation with his key takeaways:

  • Small increases in body fat lead to profound decrements in anaerobic performance
  • Untracked changes in body composition can mislead one into believing that his/her program is responsible for changes in performance. Therefore, body composition must be taken into consideration for optimal program design.
  • Keep lifting/training volume high during the competitive season
  • Monitor athletes’ body composition over the course of the season
  • Educate athletes about dietary behaviors

    I hope this was an enlightening article for you, because learning this information was a real shocker to me. I always wondered about the athletic performance implications of increases in body fat, but never saw the affect quantified.

    Be sure to share this article with your triathlete and marathon running friends!

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  • 9 Comments on “How Body Fat Affects Athletic Performance

    1. Christian
      March 7, 2012 #

      Very Insightful Article! Knew that excess body fat affected performance but never realized that little amount of body fat can make that much of a difference. Thanks

    2. mj
      March 7, 2012 #

      This was shocking, but very informative. I am working hard to lose fat without losing muscle. At my age (51) and with my current body composition (very high fat %age), it has not been easy. This gives me encouragement.

    3. Brandon
      March 9, 2012 #

      Excellent article Marc. And definitely thanks for sharing this. I’ve noticed my sprinting speed and power drastically increase with each bit of fat I lose. I feel lighter on my feet and can push myself harder every bit I lose.

    4. dave stein
      March 9, 2012 #

      I will try to incorporate this way of thinking as I coach my high school softball team starting next week.

      As usual, a very helpful article.

      Thank you, Dave

    5. Hank
      March 10, 2012 #

      Wow what great research! It makes great sense and points out, unfortunately for me, how important nutrition is in getting to the next step.

    6. yash
      March 26, 2012 #

      wow thanks bro very informative :)

      1. March 26, 2012 #

        Happy you enjoyed the article!

    7. Dimitris
      June 24, 2012 #

      Hi, Marc! Nice article indeed.
      Could you offer any insight on the ideal body fat % for boxers-MMA fighters?
      Does “the lower, the better” apply there too, or a bf around 12-14% would provide some kind of valuable antishock layer against punches,kicks?

      Thank you!

      1. June 28, 2012 #

        @Dimitris – That’s a really tough call Dimitris, because overall body weight is a factor in the fighting equation. Some fighters use their body weight as an advantage more than others, so my answer would be it depends on how much you use your body weight to your advantage. If you don’t, then yes, getting as lean as possible is ideal, so you can be as quick and strong as possible at a given body weight. This question is similar to let’s say a football player, because some positions need to be very lean and other positions like a linemen need a lot of bodyweight with some fat.

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