Blog Post: Relative Energy Deficiency in Sport

By Judith Haudum, MSc - Sport Dietician and owner of

It feels like almost everyone knows someone in cycling who does not have a menstrual cycle. When I meet with women’s teams and bring up this subject, I still see many surprised faces. There are too many stories out there of athletes losing their periods. They think it is normal and convenient to not have to worry about it every month. 

However, it is not normal to not have a period! It is a signal from your body that it is not happy or functioning in a healthy way. Luckily, this is no longer a taboo subject and we can now have productive conversations about this topic in public. 

Cyclists are at high risk of not consuming enough energy. Hard and long rides require good fuelling and additional energy intake next to training to support recovery and performance. When intake is insufficient, there is a risk that athletes experience a syndrome called Relative Energy Deficiency in Sports (RED-S). One of the symptoms of RED-S is amenorrhea, the absence of a period. While athletes tend to think they are consuming too many calories, the opposite is often true. Many athletes are not fuelling enough and finish the day with a huge caloric deficit.

Underfueling can have different causes. Some cyclists want to lose weight or optimize body composition before their first races of the season, or when targeting specific season goals. While others simply underestimate their caloric needs on training and race days.

Some cyclists notice the initial weight loss and think it is great for cycling, but over time they could end up with serious health conditions. Under-fuelling for several days, weeks or months can lead to health and performance consequences, negatively impacting every system in our bodies. 

The food we eat provides our bodies with energy to carry out basic bodily processes, such as regulating metabolism and promoting cell repair and adaptation after training. If we fail to meet energy requirements, we move into an energy saving mode, where certain processes in our body are prioritized over others. The reason a lack of a period is a sign for concern is because with RED-S, this physiological function is turned off in order to minimize energy expenditure and prioritize survival.

Bone health and the immune system are two other areas that are often impacted by this energy conservation mode. I see many endurance athletes break bones during and after their careers, and miss many training days and competitions due to injuries and illness caused by RED-S. 

Every time I see a cyclist in my clinic and she tells me she has no period, my first goal is to get it back. Athletes should not focus too much on the number on the scale, or on the percentage of body fat when striving for high performance. We can only reach our performance maximum if our body is fuelled and functioning.

No period is not normal, and is not okay. I strongly recommend that any cyclist who notices irregularities in their menstrual cycle reach out to a qualified dietitian or nutritionist for help. They can help adjust your nutrition to your training load to achieve individual goals in a safe and healthy way. It is important to prioritize health in order to achieve your best possible performance. 

TCA Members can access 1 FREE Nutrition Consultation per calendar year with Judith and benefit from a ‘preferential TCA rate’ for any additional private consultations. Please contact Judith at to arrange a meeting.

Additional information about RED-S is available here on our website:

It is also possible to watch past nutrition related webinars on the TCA website members portal.

Photo credit: Zac Williams/

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