• Hi Frank,
      I think running underweight will make you faster, but it’s at the risk of suffering bad stress fractures that could sideline you from running any way from several months to a year. If the stress fracture is bad enough, you may not even be able to run again. All this points to a lager topic that I have addressed in previous posts: training error.

      Training error occurs when an athlete trains in such a way that the body undergoes a lot of stress, such as tired muscles not getting rest, and the result is either an injury or a lengthening of time for the injury to recover. When an under weight runner runs, most of the time it’s a woman, they don’t have enough body mass to absorb the shock that is sent to their joints. The result is often a debilitating stress fracture. Most under weight athletes who have gone on to gain the recommended weight, have found themselves healthier and more able to enjoy running.

  1. Vernita Young

    Really educating post, If we forbid a food, it often makes us want it more. So I have learn to eat all foods, and learn to tune in to what I really want, not just what I think I want.

    • Hi Vernita,
      I think you make a really good point. Yes, it’s true that if we go overboard in restricting our intake of a particular food we may end up wanting more of it. I think wise advise for everyone, especially athletes, is to eat a balanced meal. For an underweight runner including more fat in the diet can be balanced with more protein and fruit, for example. The point is that your body is fueled and strengthened by different types of food. We have to pay attention to our body when it signals that something is lacking.

  2. Jamie

    Very informative and timely post. I have a daughter who is a very serious runner, and has suffered some stress fractures over the years. I have always suspected that her thinness was a big factor in her injuries.

    Your post has convinced me that I was right. She’s okay now, but I’m going to have her look at this amazing and well written post. Maybe, she’ll finally realize that it’s good idea to add some weight to her small body if she’s going to continue competitive running.

    • Hi Jamie,
      As Dr. Timothy Miller, assistant professor of clinical orthopaedic surgery and sports medicine, points out: “When body mass index is very low and muscle mass is depleted, there is nowhere for the shock of running to be absorbed other than directly into the bones. Until some muscle mass is developed and BMI is optimized, runners remain at increased risk of developing a stress fracture “ So indeed, your daughter would do well to listen to you to prevent future injuries. I wish you luck in that regard.

  3. ProlificAshley

    This is a very informative post. I really liked the story of Samantha Strong,that former collegiate triathlete and high school runner. I can’t believe that at 22 years old she had eight or nine  stress fractures over her high school and college careers. Each one, she says, took longer than the last to heal. Her story is an important reminder that the body needs enough mass to withstand the pressure that running has on the joints.

    • Hi Ashley,
      I think Samantha’s own words nicely reinforce your point. “Although Strong admits she is never far from the urges to control her eating and stay at a low weight, she is in a much better place than just a few years ago. “Since getting it out in the open and working with a nutritionist, I’ve had a growth spurt,” she says. “I put on about 15 pounds and grew two inches once I started eating.”
      Even better: She now finds joy in running and is able to maintain about 50 miles per week without injury. “I haven’t had a stress fracture in a full year,” she says. “It’s exciting to be here.”

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