It’s True: Research Shows Leaner Athletes Are Faster

Endurance sports, of course, tend to favor two related body characteristics:

  1. low body weight
  2. lean body composition (or a low body-fat level).

This is the case because endurance racing demands the ability to move economically so that a high work rate (or speed) can be sustained for a long time and a low body weight and lean body composition contribute to movement efficiency.

The advantages of being light and lean for endurance performance are so obvious that they hardly needed to be scientifically proven, but exercise scientists have gone out and proven them anyway, and the proof is interesting. Here are just a few examples.

  • Bale, Bradbury, and Colley 1986: Among 60 male runners, the fastest runners were the lightest and leanest. The heaviest, least lean runners were the slowest. And in this study, the average weight difference between the fast, average, and slow groups was just 11 pounds. The point? Just a few pounds make a big difference.
  • Knechtle et al. 2011: Body weight had a moderate effect on race times for Ironman® athletes, but body-fat percentage had a large effect on race times. Both body weight and body fat were more strongly correlated with race times, especially for run splits, than training variables like average weekly training time. The point? Your body composition matters more than how much you train.
  • A 1999 Spanish study: Performance in a flat cycling time trial is best predicted by a rider’s maximum power output, but performance in an uphill time trial is best predicted by the rider’s power-to-weight ratio. The point? If you plan to race going up, you’ll want your power-to-weight ratio to go up first.
  • Hecht et al. 2007: Researchers found that the average body-fat percentage among age-group (i.e., non-elite) participants in an Ironman triathlon was 17 percent for males and 27 percent for females. These values are lower than average for the general population, but much higher than the values seen in the pros. And sure enough, when the researchers matched body-fat percentages against finishing times, they found that the men and women with the leanest bodies were also the fastest. The point? Yes, even triathletes can improve their finish times by getting leaner.

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Racing Weight is a proven weight-management program designed specifically for endurance athletes. Revealing the latest research and drawing from the best practices of elite athletes, coach and nutritionist Matt Fitzgerald lays out six easy steps to help cyclists, triathletes, and runners lose weight without harming their training.

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