Your menstrual cycle has an impact on every aspect of your life. It can influence how you are feeling, your motivation and ease during workouts, your appetite, cravings, creativity and more. But one aspect less understood is the influence of your menstrual cycle on your metabolism. Imagine understanding your body so well, you can plan your nutrition and workout around optimizing your metabolic activity according to what stage of your menstrual cycle you are in. Yes, that’s right, science is beginning to understand the connection between a woman’s cycle and her metabolism. Here we share with you the science behind it all and how to plan ahead to make the most out of each week!
A woman’s menstrual cycle is divided into four phases. The average duration of the menstrual cycle is 28-30 days, and this can differ from cycle to cycle. A woman’s menstrual cycle is calculated by counting from the first day of her period to the day before her next period. A female generally gets her first period (known as menarche) between the ages of 11-14.
It is important to note that the scientific information this is based on is only relevant to women with regular periods. This does not apply to women in menopause, with premenstrual syndrome, polycystic ovaries, or women who suffer from irregular periods. The same goes for women who take hormonal contraceptives which play a role in changing hormone levels chemically.
A woman’s menstrual cycle is controlled by a complex communication between different glands and the hormones they produce. Within the brain is the hypothalamus. This brain structure is responsible for activating its neighbouring structure, the pituitary gland. This activity results in a chemical production prompting the ovaries to produce estrogen and progesterone.
As a form of bio-feedback, the menstrual cycle works in a way that every structure in the brain and gland involved in this cycle is affected by each other.
There are five phases of the menstrual cycle and each one has a unique impact on the body. Understanding how each phase works and how to adjust your nutrition properly can be critical to helping you achieve your goals, as well as optimizing your metabolism. The five stages of the menstrual cycle are:
When an egg is unfertilized, it creates a drop in hormone levels of estrogen and progesterone. Because there is not a pregnancy for the uterus to support, the endometrium (uterus) no longer requires this thick lining. Thus the drop in hormones triggers a shedding of this lining.
Throughout your period, you shed a combination of blood, uterus tissue and mucus. The average duration of a period is 3 – 7 days.
The follicular phase starts with the first day of menstruation, and ends with ovulation. The hypothalamus is a brain structure that prompts the neighbouring brain structure, the pituitary gland, to release the hormone FSH (follicle stimulating hormone). FSH stimulates the ovaries to produce up to 20 follicles. Follicles are tiny nodules on the surface of the ovary. Each one of these nodules will house an immature egg and one will mature into an egg. As a result of the growth of these follicles, the uterus lining is prompted to thicken to prepare for a possible pregnancy. This happens around day 10 of a 28 day cycle.
The ovulation phase occurs when the mature egg from the follicular phase is released from the surface of the ovary. This generally occurs around the middle of the cycle and around 2 weeks prior to menstruation. The development of follicles in the second phase creates a rise in estrogen. In the brain, the hypothalamus detects this hormone and responds by releasing the hormone GnRH (gonadotropin-releasing hormone). This hormone then prompts the pituitary gland to increase levels of LH (luteinising hormone) and FSH. A direct result of this rise in hormone levels triggers ovulation. The egg is then released and travels through the fallopian tube towards the uterus. The egg will survive around 24 hours, unless it is fertilized.
Days 15-23 of a woman’s monthly cycle are the post-ovulation phase. These days, progesterone and estrogen increase. On one hand, the increase in estrogen, makes women’s bodies more efficient at burning body fat due to an increase in insulin sensitivity, but on the other hand the increase in progesterone inhibits estrogen and causes a decrease in its sensitivity. This makes the effect of this phase on your metabolism uncertain and difficult to predict.
Additionally, the fat cells and small intestine also release less leptin in this phase. Leptin is a hormone that decreases hunger. This means women might experience an increase in hunger in this phase.
This phase develops within the last 6 days (approximately) of the cycle, and is characterized by significant drops in estrogen and progesterone levels. In addition, stress hormone levels (cortisol) and testosterone tend to increase.
As far as research goes, the impact of the menstrual cycle and metabolism, is something that is only beginning to be understood now. A large portion of research performed in the past has been based on looking at men and women in the same way. However today, we understand that this is not true. The difference in hormonal behaviour between the sexes are vast, and the consequences of these differences means that metabolism behaves differently for women and men. That being said, with new research we are beginning to understand how the female metabolism responds to the different phases of the menstrual cycle.
The two main hormones that play a key role in the menstrual cycle are estrogen (in particular estradiol) and progesterone. The two major hormones related to this are LH and FSH. Depending on the variation of these hormones, they signal for different responses in estrogen and progesterone at different times.
The type of metabolic fuel your body is using will depend a lot on insulin sensitivity. When a person has a high insulin sensitivity, cells can utilize blood glucose more effectively. Research shows that estrogen has a significant impact on insulin sensitivity, meaning that by knowing where you are in your cycle, you can control the influence of this phase on your hormones, and in turn your insulin sensitivity. By understanding your changes in fuel oxidation (whether you’re burning carbs or fat), you can plan the way you and your workouts according to your cycle, therefore going with and not against your body.
Science is only now beginning to expose the effects of the interaction between estrogen and progesterone. Here is what we understand so far:
During the first phase of the menstrual cycle, you have phase 1 (menstruation), where estrogen levels dip, and phase 2 (the estrogenic phase) where estrogen peaks. Moreover, the ovulatory phase causes a peak in FSH and LH. Followed by phase 4 (the postovulatory phase). During this time estrogen levels rise and progesterone peaks. Lastly, the pre menstrual phase takes place during the last days of the cycle where the progesterone and estrogen levels drop off again, leading to a new cycle.
This rise and dip in estrogen plays an important role in insulin sensitivity and therefore metabolism.
It has been theorized that estradiol enhances the metabolism of fat. There have been some studies that have examined this relationship between the menstrual cycle phases and metabolism at rest. These studies have found lower RER in phase 2 (the estrogenic phase) of the menstrual cycle when estrogen levels peaks
The menstrual cycle begins with the first day of your period. During this phase, progesterone and estrogen production drops off .
Due to decreased energy levels, this is a time in your cycle to listen to and work with your body and rest if needed. This may be the best time to integrate your rest days. However gentle exercise such as yoga or a gentle walk can help improve energy levels and keep you feeling well. Avoid intense workouts and heavy lifting as the increase of estrogen levels can also make you more prone to injury.
During this phase it is important to pay special attention to your iron intake, as menstrual bleeding increases women’s iron intake due to blood loss. Iron is a mineral that can be found in many foods such as lentils, green veggies, eggs, liver, meat, broccoli, and figs – among many others-. During this phase inflammation levels can also rise, for that reason it’s recommended to include foods with anti-inflammatory properties such as ginger, turmeric, green tea, among others.
Between days 7-14, women are generally in the estrogenic phase. In this phase estrogen levels increase and as a result insulin sensitivity increases. This increase in hormones provides you with a higher level or energy and this can be used to your advantage.
This is your time to shine. Take full advantage of your peaking energy levels and opt for workouts that make you break a sweat. Workouts like HIIT (high intensity interval training), spinning classes and cardio are great exercises to take part in during this time. It is important to note that the rise in estrogen levels can slightly increase injury and so it is important to always listen to your body, especially during high intensity workouts.
Because you experience more insulin sensitivity, this phase is optimal for boosting your body’s ability to burn fat. For that reason, you should prioritize healthy fats which are rich in omega 3 and omega 9, like fish, avocado, nuts and extra virgin olive oil.
During this phase of the menstrual cycle, there is a natural tendency for the body to store more fat due to the release of a hormone called adipsin. Also, women can experience more hunger due to a slight increase in the basal metabolic rate that occurs.
Due to the fact that the body is less efficient at burning fats during this phase, it is recommended to avoid endurance training and focus more on exercises of moderate intensities.
Focus on slow-absorption carbs, they are full of fiber and also micronutrients (vitamins and minerals) which will help you feel satiated and also provide you energy for your daily activities .
The postovulatory phase takes place during the second half of the menstrual cycle and after ovulation. In general this occurs on day 15 of the cycle. During this time progesterone rises, in turn decreasing insulin sensitivity. This makes you less tolerant to carbohydrates. Additionally during this phase proteolysis is stimulated (the breakdown of proteins). Therefore your diet should reflect this.
Furthermore during this phase women often experience food cravings and the release of stress hormones. This may reflect a greater reliance on carbs oxidation where the metabolism uses carbs as an energy source. Focus on foods to curb cravings such as high fibre and/or protein rich foods, some great options can be Quinoa, beans, tofu, cottage cheese and meat. Also, be mindful of how much you’re drinking. Keep in mind that an increased body temperature may cause you to sweat and lose water. Make sure you drink at least 8 glasses of water every day.
During this phase, you may experience a bigger appetite, drink plenty of water and choose protein found in low-fat cheese, yogurt, edamame, peanuts, and chia pudding. Be sure to eat healthy fats like fatty fish, pure cacao, eggs, avocado, and flaxseed oil to meet your energy needs and improve your metabolic flexibility.
First and foremost you should definitely learn about you and your cycle. A great way to do this is to either keep a diary or use a menstrual tracker. Flo is a great option for this as it not only helps you track your menstrual cycle, but it also helps with predictions of your period and ovulation and gives you some pretty useful insights about the phase that you are in.
Understanding where you are in your monthly cycle can help you understand how to plan your workouts and prepare for those difficult binge and cravings. Preparation is one of the keys to success when it comes to weight loss and keeping healthy.
Because the biological process behind a woman’s menstrual cycle is so complicated and individual, science still has a way to go to be able to provide an individualized breakdown of the impact of your cycle on your metabolism. However, that doesn’t mean you cannot not use the knowledge science has gathered so far to be prepared. Personal tracking both with Lumen and of your cycle is a great way to explore your metabolism’s reaction to your cycle and the hormones behind it. By doing so this connection becomes clearer and you can understand you far better, and do something about it. The power is in your hands (and breath)!