Debunking the Race Weight Myth in Sports

January 4, 2024 ,

Many endurance athletes think that they need to lose weight and reach a target race weight to be as fast as possible, for example to run a marathon. But it’s not that simple!

Two people with the same weight can look and perform very differently depending on their body composition, i.e. muscle mass, fat mass, and water weight. Having optimal muscle mass and being well hydrated will add weight to the scale, but it will also help optimise athletic performance.

Another crucial aspect to consider is the method used to lose weight. A constant calorie deficit will impair athletic performance and can have serious long-term health effects.


Prolonged low energy availability, called RED-S (Relative Energy Deficiency in Sport) occurs when an individual’s dietary energy intake is insufficient to support the energy expenditure required for health and daily living activities, once the cost of exercise is taken into account. This can negatively affect metabolic, reproductive, gastrointestinal, neurocognitive, cardiovascular, immune, muscle, and bone functions. More specifically, this can lead to detrimental consequences including nutritional deficiencies, decreased bone density, reduced immunity, increased risk of injury, and decreased athletic performance.

Here are some potential indicators of RED-S:

  • In women: secondary amenorrhea (absence of 3 consecutive menstrual cycles)
  • In men: low testosterone levels, reduced libido, decreased morning erections
  • Low bone density, stress fractures
  • Anemia
  • Anxiety, mood swings, sleep disturbances
  • Low blood pressure, extreme bradycardia (heart rate <40)
  • High cortisol levels
  • Hypoglycemia

The prevalence of RED-S ranges from 15 to 80% in athletes depending on the sport. This syndrome remains relatively unknown among athletes, coaches and health professionals. It can be unintentionally exacerbated by a “sports culture” due to perceived short-term performance gains when limiting calorie intake. The LEAF-Q or LEAM-Q (Low Energy Availability in Female or Male Questionnaire) is a tool that can be used to screen for RED-S.

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Kathryn Adel
Kathryn holds a Bachelor Degree in Nutrition as well as a Bachelor and a Master Degree in Kinesiology, all from Laval University. She is a Registered Dietitian and active member of the Ordre professionnel des Diététistes Nutritionnistes du Québec (ODNQ) and of the American Academy of Nutrition and Dietetics. She holds the Monash University's certification for the FODMAP diet and IBS, and has considerable clinical experience in that area. She is also an accomplished athlete, having ran track and cross-country at a national level. Kathryn specializes in sports nutrition, weight loss, diabetes, as well as heart and gastrointestinal health.

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