Health, Nutrition, Podcast, Science

RED-S (Relative Energy Deficiency in Sports) with Margo Mountjoy | EP#233

 May 11, 2020

By  Mikael Eriksson



In this Episode you'll learn about:

  • Health and performance consequences of RED-S
  • The root cause of RED-S: energy deficincy
  • Prevalence, risk groups and risk factors, and early warning signs of RED-S
  • RED-S in female and male athletes - beyond the female athlete triad
  • How to avoid RED-S
  • Energy deficiency and calorie deficit: what is an acceptable range during periods of weight loss?
  • Screening and diagnosis, treatment, and recovery time course of RED-S

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About Margo Mountjoy

05:00 - 

  • I am a sports medicine physician who mainly works with endurance athletes like runners, cyclists, swimmers and triathletes.

    I am as well a scientist and have a Phd in sports medicine and my main field of research is energy deficiency and other health related topics for athletes.

Relative Energy Deficiency in Sports (RED-S)

05:45 -

  • In 1980, a phenomenon known as the female athlete triad was discovered by an American researcher.

    The triad constitutes of eating disorders, osteoporoses and amenorrhea, but during the years the definition of the syndrome has changed so you don’t have to fulfill all three components for being diagnosed with the condition.

    After the issue was thoroughly reviewed in 2014, we found that the core of the problem is lack of energy availability and that plenty of more body systems were affected than the bones as well as the reproductive system, moreover we also found that the condition affected males.

    Given this, the syndrome was no longer deemed suited to be called the female triad and hence, the term RED-S (Relative Energy Deficiency in Sports) was created.
  • RED-S can either be caused by an over expenditure of energy (over exercising) or by under fueling (either consciously or subconsciously), the latter one is actually the most common reason, many people engaged in endurance sports do not fully realize how much they need to replenish in order to keep up with their energy expenditure.
  • Definition wise, RED-S can be explained as a lack of energy to support the exercise after daily functions such as basic metabolism, walking, working etc. have been supported.

    What needs to be understated is that appetite is a rather poor predictor of how much energy we need to take in, many athletes that I meet are claiming that they eat a lot and are rarely in a state of hunger and despite this, they are showing signs of RED-S.
  • For the average triathlete, who do not have the time or resources to exactly balance their energy output and intake, a good way to keep track of the balance is to follow your weight development daily, which if it stays the same is a fairly good indicator of energy balance.

    Another aspect that the average triathlete could consider is to eat food with a high energy density and to try and eat frequently during the day.
  • It’s fine if one wants to reach a lean body composition for a certain competition, and this can be achieved by highly controlling the energy intake over a time of 1-2 months leading up to the event.

    However, one should not strive to have that lean body composition throughout the year as that could pose a serious health threat (e.g. more injury prone and immunosuppression) as well as it is not optimal for performance (body does not seem to react as well to training stimuli etc.).

    One injury risk that is extra large for athletes with RED-S is the risk for bone related injuries, especially stress fractures, which unfortunately are not too uncommon within triathlon.

Calculating energy requirements

22:30 -

  • If one wants to approximate the basic metabolism, a good estimate is to multiply your fat free weight in kg:s with 45 to get your daily calorie needs before compensating for any extra activities.

    We can take Mikael as an example, he weighs 67 kg and may be around 10 % body fat, so rounding up his fat free weight is 60 kg.

    60x45 equals 2700, which is his daily calorie needs a day when he doesn’t train, which is a fairly high energy intake.
  • I found that most people underestimate how much energy they are taking in both by portion size and energy content in the food they eat.

Potential health complications following RED-S

23:45 -

  • Health complications linked to RED-S include menstrual (in women) and sexual dysfunction, bone health, other endocrine dysfunctions (the reproductive systems typically is affected first), metabolic consequences, hematological impacts, suppressed growth and development (in young athletes), psychological effects, impacts on the cardiovascular system (mostly related to endothelial function and the development of atherosclerosis), gastrointestinal and immunological issues.

    Hence, a lot of systems can be affected but it is important to underline that in most people with RED-S, all of these systems are not affected, it can only be one or two systems that show signs of the condition.
  • In women, menstrual function is usually the first sign of RED-S.

    Correspondingly, testosteron plasma levels in males are one of the first signs of RED-S in males.

    Signs of low testosteron levels include fatigue, decreased performance, reduced sex drive, lack of morning erection etc.
  • Among endurance athletes women, irregular menstrual cycles are unfortunately very common and I would like to understate that this is not a normal state among women and should not be normalized under any circumstances.

    The most common reason for missed menstruations is pregnancy, so this is what needs to be checked first in an athlete whose menstruation is absent.

    The second most common reason, however, is lack of energy availability.

    It can be okey health wise to be in a state of infrequent menstruations for maybe a month or two while one is trying to reach a lean body weight for a certain competition but always suffering from irregular or absent menstruations does pose certain health risks and is moreover not optimal for performance.

    I encourage all women who have had 2-3 absent or irregular menstruations to seek medical counseling,
  • It’s hard to say if a state of over training or over reaching while energy availability is still sufficient can lead to the same symptoms as RED-S, I think that in the years the come, the research will find that these different conditions are very closely linked to each other.
  • In terms of how long time it takes for an athlete to be in a state of RED-S until it starts posing health threats are very hard to know, plenty different factors come into play such as age, training volume, familiarity of high training volumes, other individual factors etc.

Getting into race weight

35:00 -

  • If someone wants to reach that ”optimal race weight” where they perform at their absolute peak of their ability, there is a ”right” way to do it, a ”wrong” way to do it and a ”terrible” way to do it.

    Firstly, it should be done over a longer period of time, 2-3 months and NOT 1-2 weeks.

    Secondly, one should make sure to take in all important macro nutrients, including carbohydrates, proteins and fats.

    ”Empty calories” such as treats are the ones that is recommended that one cuts first in this process.

    When the process is done right it is fairly risk free but after the key event the recommendation is that the weight that was being lost is gained rather quickly.
  • If someone wishes to loose more weight than just a couple of kg:s (if that is possible), one should just focus on eating a healthy and a balanced diet with an emphasize on large amount of vegetables and at the same time engage in activities that brings plenty of joy.

    If this is doing correctly, one should then loose around half a kg per week, a higher weight lost is generally not sustainable and/or healthy.

    However, it’s probably better to focus on the health benefits that a good activity level leads to that is not directly related to body composition than just weight itself.

The prevalence of RED-S

39:55 -

  • It’s very hard to say how prevalent RED-S is since it is extremely sport dependent, sports where performance is highly dependent on weight or sports that implement weight classes as well as sports where looks matter a lot (like figure skating and diving) are known to be at greater risk.

    Another risk group is also people who practice sports very much on their own, and are not surrounded by a team of for instance physicians, dietitians, coaches etc. that can monitor the athletes closely.


44:15 -

  • The main treatment for RED-S is to ensure to reverse the lack of energy availability, which is extremely logical, however, one needs to point out that if there is an eating disorder behind the RED-S, then completely different measures need to be undertaken.
  • The typical time it takes for a female athlete who is suffering from RED-S and has had amenorrhea to get her menstrual function back is about 3-6 months.

    When it comes to bone function it takes about a year until the bones has recovered properly.

    In males, the recovery times seems to be slightly shorter.


50:20 -

  • RED-S is highly preventive by having a proper diet, doing a sensible amount of training as well as spreading the knowledge about the condition so that it reaches the broad mass.
  • When it comes to if one should weigh oneself every day or not to keep track of weight patterns, I am very divided about this.

    For people who keep track of their weight to ensure that they are not loosing weight, it can be a good thing, but for those on the other hand that do this in order to try and loose some weight there is clearly a risk with that.

    For amateur athletes my advice is that they weigh themselves once a week to ensure that the weight is staying roughly the same, for elite athletes, one may need to be more diligent about this and weigh in daily.

Rapid fire questions

55:50 -

  • What is your favorite book, blog or resource related to endurance sports? I normally restrict my reading to scientific literature but I can warmly recommend to follow people like for instance Louise Burke on social media, they are great at translating science so that is is understandable for regular people.
  • What is a personal habit that has helped you achieve success? Persistence, never giving up, hard work and keeping my eyes on my goals.
  • What do you wish you have known or done differently in your career? I actually don’t have any regrets, I have been an elite athlete and enjoyed that very much and then I moved into medicine and sports medicine, which I also have enjoyed thoroughly.


Mikael Eriksson

I am a full-time triathlon coach, founder of Scientific Triathlon, and host of the top-rated podcast That Triathlon Show. I am from Finland but live in Lisbon, Portugal.

Please contact me if you have feedback on the podcast or want to make suggestions for improvement or send in a question for a Q&A episode.

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  • I really wish she’d gone into more detail about how they are cutting a pound a week off of their athletes without causing RED-S and significantly reducing performance. I am still so confused about how to do this well after reading tons of books and resources on the topic.

  • Thank you for episode #233 on RED-S. One cause of unwitting under fueling could be undiagnosed celiac disease. Celiac is not rare, and mostly undiagnosed. Trying to train for endurance sport while not realizing your body is not able to take in nutrition sends health off the rails. It happened to me. Thanks for your show.

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