Why do female athletes sometimes lose their menstrual cycle?

Let’s begin with the most important point – we don’t want female athletes (or any female) losing their menstrual cycle.

While life might be somewhat more pleasant without menstruation, it is not a sign of good health to have an absent cycle.

Never discount an underlying medical reason:
Firstly, a medical reason for loss of menstruation should be ruled out. Loss of menstruation for an athlete can be investigated by a sports physician and they should always be your first port of call.

Why does the menstrual cycle disappear in the absence of a medical reason?
Our lungs don’t respire without access to energy, our liver doesn’t cleanse without access to energy, our kidneys don’t filter without access to energy…. same goes for the menstrual cycle. Our body is like a car, without petrol.. we stop.

The difference between our menstrual cycle and any other bodily function is that if our menstrual cycle stops, we don’t die. Sure, we can’t produce life (a child) without it, but we ourselves don’t die. Imagine if our lungs stopped respiring or our liver or kidneys stopped.. we wouldn’t last too long in the absence of these daily functions.

So, essentially, our menstrual cycle will cease if there is not enough energy left over to complete this function as the body knows it is not a function that is essential to keeping us alive.

Why wouldn’t we have enough energy to menstruate?
This comes down to how much we eat (food contains energy in the form of kilojoules or calories) relative to how much we exercise (energy is burned up through bodily functions, incidental movement and purposeful movement each day).

If our food intake is < our daily needs, eventually the menstrual cycle will be sacrificed in order to conserve energy for life sustaining bodily functions (such as the lungs, liver and kidneys – as mentioned earlier).

How do I know how much I need to eat to cover my needs?
Well, this is a really difficult question. Measuring your energy requirements can only be performed accurately in a lab setting (yes, sorry, fitness trackers and watches aren’t very accurate!) Anddd, it is very difficult to re-create your normal daily life and activities within a lab!

In this case, we can’t aim for perfection (nor should we want to, when it comes to food), but we can aim for a range that is likely adequate and monitor the menstrual cycle to assess the result.

An Accredited Sports Dietitian can assist you with this, or you can experiment yourself – slowly increasing your usual dietary intake until your menstrual cycle becomes regular again. A regular menstrual cycle is considered ~21-35 days apart. There are many apps that allow you to track your cycle so that you can stay on top of it. In fact, many elite sports programs these days incorporate menstrual tracking in their female programs for the very reason of ensuring its regularity.

Wait, so why is it important to have a regular cycle?
Well, not only is reproductive function affected, but hormonally a lot changes without a cycle. For starters, estrogen levels are lower and this has an impact on bone turnover. Over time, in the presence of low estrogen, bone breakdown exceeds bone accretion, and you might end up with a higher propensity for bone injuries such as stress reactions and stress fractures (and therefore a lot of time off training). Not having enough energy to menstruate also can mean you don’t have enough energy for optimal immune function, leaving you more susceptible to colds and flus (and hence more time off training). Not having enough energy can also leave you irritable or with feelings of low mood. In fact, the list goes on. Inadequate energy intake can affect most systems of the body. That’s why it’s important to celebrate your monthly cycle – it is a sign of good health for more reasons than one 🙂

Please note: The pill and some contraceptive options such as IUD’s affect the menstrual cycle, so if you are using any of these, it is difficult to know if you actually have a normal monthly cycle even if you do bleed monthly. Frequent colds/flus, recurring bone stress injuries, persistent irritability or low mood, poor recovery from sessions and unexplained drops in sports performance may be other signs to look for in this instance.