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Relative Energy Deficiency in Sport

A collage of swimming photos of Coach Rebecca across the years. From a little girl swimming in the pool, to youth swimming as part of a relay, to high school swimming at Bolles.

I loved being in the water from an early age.

My Personal Story as an Athlete with RED-S

It was a running joke amongst my roommates in college that it took a year for us to go through one shared box of tampons in our apartment.  I was swimming 20 – 25 hours per week across 10 sessions per week.  I kept a training log, and if I didn’t hit 80,000 meters of swimming in the week, I worried that I would get out of shape.  I ate whenever I was hungry which was always.  I think the whole athletic department shared one sports dietician.  I remember him stopping by practice once per year before we took our annual three-week training trip to Hawaii to discuss fueling tactics for training camp.  Fueling tactics included horrible tasting shakes of which the coaches brought several cases to camp.  The coaches decided who needed shakes and who didn’t.  A lot of the men on the team had the shakes, but I only remember a handful of women chosen for shakes.

Long story short, the education around sports nutrition for Division 1 athletes at the time was dismal at best.  To be fair it was the early 2000’s, and we as a sports community know a lot more today about RED-S and the importance of proper fueling for optimal sports performance.  However, despite the knowledge we have today, there are still many coaches at all different levels spewing the old adage that smaller is better and faster.

So, what is RED-S anyway and why is it so important?

The International Olympic Committee Consensus group defined Relative energy deficiency in sport (RED-S) as “impaired physiological function including, but not limited to, metabolic rate, menstrual function, bone health, immunity, protein synthesis, and cardiovascular health caused by relative energy deficiency (Mountjoy et al 2014).”

In female athletes a normal menstrual cycle depends on an intact hypothalamic-pituitary-ovarian axis (Gordon 2010, Gordon et al 2017).  The hypothalamus is referred to as the master gland because it is responsible for several downstream hormones in multiple organ systems.  Exercise can impact the hypothalamic-pituitary-ovarian axis and may impact ovulation (Hakimi 2017).  Exercise-related menstrual disturbances can include a range that is more far reaching and complex than simply not having periods.  It can include shortening of the luteal phase, anovulation, and oligomenorrhea (Hakimi 2017).

From a performance perspective, research has shown RED-S to negatively impact sports performance in both male and female athletes.  For example, Drew et al. found that low energy availability was associated with health disorders and disruptions in training schedules in Olympic-class male and female athletes (2018). Likewise, Ackerman et al. reported that low energy availability was associated with aspects of declining performance (decreased training response/endurance performance, impaired judgment, decreased coordination and con-
centration, irritability, and depression) (2019).

After starting my period at age 13, I was really starting to get serious about my swimming training.  I went to boarding school in high school at a renowned swimming school with an ethos of training BIG yardage.  Some mornings we swam 10,000 yards all before school started and followed that up with three hours of swimming after school.  I distinctly remember swimming a practice once towards the end of the school year and realizing I hadn’t had my period the whole school year.  Dorm food was not very appealing, so our food intake was not all that nutrient dense.  I ate my weight in boxed cereal and granola bars.  We had mandatory weigh-ins with the whole team lined up behind you which was mortifying.  I remember the coaches nodding in approvement when I stepped on the scale.  I also remember a few girls who were chosen to do more cardio after weigh-ins.  They had to run in addition to the five hours of swimming we did per day!

In college we didn’t have mandatory weigh-ins but we were encouraged to weigh ourselves regularly.  When we had travel meets dinner would be catered at the hotel.  Once there was a plate of cookies brought out for dessert and we all started to beeline towards them.  One of the coaches asked the server to take the cookies away.  I still wish to this day I taken a damn cookie!

From 13 – 21 years old I averaged anywhere from 2 – 4 periods per year.  When my period did come it was usually when we were tapering or in the off season when training load would decrease.  After graduating college and retiring from swimming, I started racing triathlons and bought a new bike.   I noticed some lower back pain when doing long rides after several months of feeling comfy and well-fitted on the bike.  I went back to see if the bike fit needed to be adjusted and we realized that I had grown over one inch in height.  I will never forget the look of shock on the bike fitter’s face that a 23-year-old woman was still growing.  I was working at a local running store at the time, and when one of my former college coaches came in for running shoes, I told him about my growing over an inch.  By that point I had asked around with some of my former teammates and some of them had reported growing after college as well.  The coach responded that he thought it was cool that we had trained hard enough to stunt our growth. I’m not sure why I expected a different response.

I have experienced some long-term effects from my history with RED-S.  I experienced several bone stress injuries when I started triathlon and running after retiring from swimming.  I have also noticed that I am very sensitive to increases in training load.  I begin to feel tired quite easily and instead of losing my period, the cycle will be irregular (21 – 22 days vs. 28) until I decrease my training load.  After several discussions with my sports medicine physician about this, he suggested that while the long-term impacts are not catastrophic, I am at increased risk of experiencing RED-S now and in the future compared to an athlete without a history of RED-S.  Basically, I have to be very careful with my training load – recovery balance as well as pay very close attention to my nutrition intake.


What are the lessons? And what can athletes do to avoid RED-S?


  • Education

When athletes have a very high training volume (I averaged 20 – 25 hours per week of swimming) underfueling can happen intentionally as well as unintentionally.  The amount of calories required when training 20 – 25 hours per week is massive.  Unfortunately, many coaches continue to support the notion that lighter is better in sport despite no science backing this up.  Sports performance research supports a well-fueled athlete will perform better than an athlete with RED-S.  We need to talk more about fueling and less about body weight.


  • Monitoring symptoms and metrics

The most obvious sign for female athletes with RED-S is either the absence of a period or irregular periods.  However, there are other symptoms that are important to discuss as RED-S also happens to male athletes.  Other symptoms may include fatigue, impaired performances, muscle soreness that does not go away, feeling cold all the time, heightened anxiety, and/or poor sleep.  Track metrics daily so you have a record of fatigue, muscle soreness, etc. This can provide a useful context when making decisions about your future training sessions.


  • Consult the right professionals

Build the right team around you.  Health professionals such as a sports dietician and sports medicine physician can provide evidence-backed advice to ensure you are healthy in the long term and also perform at your best.




Ackerman KE, Holtzman B, Cooper KM, Flynn EF, Bruinvels G, Tenforde AS et al (2019) Low energy availability surrogates correlate with health and performance consequences of relative energy deficiency in sport. Br J Sports Med 53:628–633

Drew M, Vlahovich N, Hughes D, Appaneal R, Burke LM, Lundy B et al (2018) Prevalence of illness, poor mental health and sleep quality and low energy availability prior to the 2016 Summer Olympic Games. Br J Sports Med 52:47–53

Gordon CM (2010) Clinical practice. Functional hypothalamic amenorrhea. N Engl J Med 363:365–371

Gordon CM, Ackerman KE, Berga SL, Kaplan JR, Mastorakos G, Misra M et al (2017) Functional hypothalamic amenorrhea: an endocrine society clinical practice guideline. J Clin Endocrinol Metab 102:1413–1439

Hakimi O, Cameron LC (2017) Effect of exercise on ovulation: a systematic review. Sports Med 47:1555–1567

Mountjoy M, Sundgot-Borgen J, Burke L, Carter S, Constantini N, Lebrun C et al (2014) The IOC consensus statement: beyond the female athlete triad–relative energy deficiency in sport (RED-
S). Br J Sports Med 48:491–497

2 thoughts on “Relative Energy Deficiency in Sport”

  1. Thanks for sharing your story. Makes me very sad that this was tolerated and is still today despite all that we know how important estrogen and having periods is for growth, mood and bone health. You may want to share this information w/ your GYN and get a baseline bone density. Have you read Dr Stacey Sims, PHD? She has talked a lot on this issue.

    1. Thanks for your comment Maureen! Will chat to my GYN at my next annual. I really enjoyed Stacey Sims’ book Roar, and have been meaning to get her next book. Hope you are well!

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