Optimizing Performance: Fueling Your Training Across the Menstrual Cycle
When we think of the menstrual cycle, it’s common to think just about having a period. But there is more to the menstrual cycle than just a period, with various changes taking place within our body throughout the cycle. Understanding the menstrual cycle and its effects on our training can actually help us to use our physiology to benefit our performance and support our goals.
How hormones affect our metabolism and nutrition needs
A majority of changes in strength, performance and recovery seen throughout the menstrual cycle are attributable to the fluctuations in hormones oestrogen and progesterone. Aside from their roles in reproductive health, oestrogen and progesterone have multiple other effects on our physiology, including metabolism.
Oestrogen:
In the late follicular phase, there is an increase in oestrogen, with it peaking at ovulation, and this is associated with some positive benefits when it comes to training. Oestrogen is associated with increased energy levels, and improved recovery from exercise (1) and is considered anabolic, meaning that it supports muscle growth (2). To benefit from the muscle-building benefits of oestrogen, ensure to include enough protein throughout the day, and particularly after a workout to promote muscle protein synthesis.
When we exercise at higher intensities, carbohydrates are typically our preferred fuel source. Research has demonstrated that oestrogen can influence the levels of carbohydrates available for fuel (3; 4, 5). During the luteal phase, the second phase of the cycle, oestrogen rises again after dipping shortly after ovulation. As a result of this, women rely less on carbohydrates and more on fats as a fuel source both at rest and during exercise during the luteal phase.
This can be beneficial for long endurance events but this can limit performance and make it challenging to push to higher intensities, as carbohydrates are the main fuel provider for intense exercise. However, consuming carbohydrates prior to exercise can improve carbohydrate availability, so carbohydrates should be prioritised (as always) in your pre-workout meal.
The increased reliance on fat during the luteal phase emphasises the importance of consuming sufficient dietary fat to account for this increased use, but fat also plays an important role in exercise recovery, as intramuscular concentrations of lipids can be depleted following exercise, which can hinder subsequent performance if not restored efficiently (6). It is recommended that 20-35% of our dietary intake comes from fat, and this can be achieved by including fat sources at each main meal such as avocado, eggs, salmon, nuts and seeds etc. at meals.
Studies have observed lower appetite levels throughout the follicular phase in comparison to the luteal phase of the menstrual cycle, and this is expected to be attributable to the high oestrogen levels towards the end of the follicular phase (7). If you are training hard, be mindful that you are supporting your overall energy and nutrient needs, as a lower appetite may lead to an insufficient intake.
Progesterone:
Progesterone peaks during the early luteal phase, which is associated with less favourable effects than oestrogen when it comes to supporting our training, and can even counteract the effects of oestrogen (5).
Progesterone is thought to be catabolic, meaning that it encourages the breakdown of muscle proteins. During the luteal phase, where oestrogen and progesterone are high, there is increased protein breakdown at rest (8), but also during exercise (9). Specifically, it has been shown that females require more lysine, an essential amino acid, during the luteal phase in comparison to the follicular phase (10) which is most likely attributable to the increased amino acid use caused by progesterone.
Although protein intake is important to consider in general, particularly when you’re active, it is really important to ensure that you are getting adequate protein throughout the second half of your cycle to accommodate these increased demands and prevent excess muscle protein breakdown (8). The quality of these proteins is important to consider too to ensure that all essential amino acids are provided.
Progesterone is associated with an increase in body temperature, and studies have identified that this can lead to fatigue quicker in endurance and strength focussed sports (11). With this in mind, hydration and intra-workout fuelling may be of increased importance in preventing negative effects on performance, particularly in more challenging sessions.
Intra-workout fuelling refers to the consumption of carbohydrates during a session to help prevent depleting stored carbohydrate levels, and therefore, preventing a drop in performance. A handful of dried fruit or jellies, a banana or an isotonic sports drink can often provide sufficient carbohydrates to keep these stores topped up throughout a session.
With this rise in temperature, progesterone is linked with contributing to an increased metabolic rate during the luteal phase (12) which means that the amount of energy you burn at rest is higher. Various studies have found increases within the range of 2-20% but this of course will vary among women and will be influenced by other factors such as body composition, genetics and physical activity levels (3, 5, 13, 14, 15).
In an attempt by the body to acquire this additional energy, it is common to experience increased levels of hunger in the lead-up to menstruation. Many women can find this increase in hunger frustrating, as it may show up as cravings for specific foods (…like chocolate!). Cravings for high-carb and fat foods are common as these foods are typically energy dense, which is what the body is seeking during this time.
So, if you do experience this increase in appetite, please have some self-compassion and honour your hunger. We know that the more we resist cravings, the more likely we are to overdo it on that food when we eventually allow ourselves to have it. This is why tracking your cycle can be helpful, as you can understand and predict any changes in your body, and make sure to account for this through your nutrition.
In the context of the menstrual cycle
In the follicular phase, carbohydrates are the dominant fuel provider, and the levels of carbohydrates required will depend on the intensity and type of sport. As much as it is important for total carbohydrate intake to be met, the timing of carbohydrate consumption can benefit both performance and health. Consuming carbohydrates prior to a training session ensures there is carbohydrate available to provide energy for the workout, consuming during a workout can help to ensure that performance is sustained by ‘topping up’ levels of carbohydrates in the body and consuming carbohydrates after a workout can support the replenishment of glycogen stores, which is most efficient in the hours after a workout (16).
In the luteal phase, fat is favoured as a fuel source and the rate of protein breakdown is higher than normal, and as a result of this, the overall metabolic rate is increased. In this phase, it is recommended to increase protein consumption to promote muscle growth and repair (18). Particular attention should also be paid to fatty acids. Fats are not only important for providing energy, but also play a vital role in sex hormone production and providing fat-soluble vitamins A, D, E and K., and are utilised more during the luteal phase.
Protein and fats are helpful for promoting satiety and should be included alongside a source of complex carbohydrates at main meals. This can help with the increased appetite that can be caused by high levels of progesterone and balance blood sugar levels, which can prevent cravings which are also common in the lead-up to a period.
The increased reliance on fat as a fuel source does not discount the need for carbohydrates during this period! Carbohydrates are still essential to health and can support our performance and recovery.
Takeaway
Research from well-controlled studies of women throughout different phases in the menstrual cycle suggest that carbohydrate and fat usage is actually similar in both phases (3, 19, 20), but being aware of the preference of fuel sources due to the role hormones play can help women use their physiology to support their training and emphasises the importance of how our nutrition can enhance our performance!
References:
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