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I often get the question: How much does an extra pound slow you down? Yes, studies do show that carrying excess weight can slow you down. The classic study that’s often cited is by Kirk Cureton and his colleagues at the University of Georgia back in 1978. They added an extra 5, 10, or 15 percent to the body weight of their subjects with a harness attached to their waist and shoulders during a 12-minute run performance. They calculated that every extra pound carried added an extra 1.4 second per mile.

But it’s not that simple!

It’s hard to know how well the extrapolations would hold at different paces, distances, sports (bike vs. swim vs. run) and weights.

Most importantly, two people who have the same weight can look and perform very differently depending on their actual body composition, meaning their muscle mass, fat mass, and water weight. Having a good muscle mass and being well-hydrated will add weight on the scale, but will also help optimize performance.

Another crucial aspect to consider before you try to lose weight is the danger of under-fueling. Being in a consistent caloric deficit will impair performance and can have serious health effects.


Prolonged and/or severe low energy availability, named RED-S (Relative Energy Deficiency in Sport), happens when an individual’s dietary energy intake is insufficient to support the energy expenditure required for health, function, and daily living once the cost of exercise and sporting activities is considered. It leads to detrimental outcomes including decreased metabolic function, reproductive function, musculoskeletal health, immunity, glycogen synthesis, and cardiovascular and haematological health, which can all individually and synergistically lead to impaired well-being, increased injury risk, and decreased sports performance.

Below is a list of potential indicators of RED-S (including, but not limited to):

  • In females, secondary amenorrhea (absence of 3 to 11 consecutive menstrual cycles) or oligomenorrhea (>35 days between periods for a maximum of 8 periods/year)

  • In males, sub-clinically low free or total testosterone (within the lowest quartile of the laboratory and age-specific reference range), reduced or low libido/sex drive or decreased morning erections

  • Repeated stress fractures

  • Chronically low iron

  • Elevated total or LDL cholesterol

  • Psychological symptoms (increased stress, anxiety, mood changes, body dissatisfaction and/or body dysmorphia)

  • Sleep disturbances

  • Exercise dependence/addiction

  • Extreme bradycardia (HR<40 in adult athletes; HR<50 in athletes under 18 years old)

  • Low systolic or diastolic blood pressure (<90/60mmHg)

  • Urinary incontinence (females)

Feeling the strongest and fastest that you can be comes naturally through training and eating well. Focusing too much on weight loss can lead to disordered eating and an unhealthy relationship with foods. Lastly, trying to have a particular number show up on the scale causes loss of focus on the ultimate goals: improved performance and overall health.

Want to hear more about this topic?

Join us for a FREE virtual clinic on October 16 at 8pm Eastern. Axes dietitians Kathryn Adel and Janet Carter will dive into the discussion in more detail, including:

  • Race weight: Is weighing less always better?

  • Body composition and how to determine ideal race weight

  • RED-S and the dangers of under-fueling

  • How to get to your ideal race weight safely without compromising performance

  • Disordered eating vs. intuitive eating

We are opening this monthly clinic to the public, so feel free to share with a friend!


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