Hormones and Metabolism in the Menstrual Cycle

Pink blocks spelling out "hormones" with flower in corner

What are the female hormones?

Hormones are chemicals produced in the body that send signals to and influence other parts of the body.  Females have four primary hormones involved in the reproductive system: estrogen, progesterone, follicle-stimulating hormone (FSH), and luteinizing hormone. 

For the purposes of this post, we will focus on estrogen and progesterone as they are the two that impact nutrient metabolism, body heat regulation, how easily we are fatigued, and exercise recovery. Ever wonder why workouts are so much harder right before your period? Read on!

Note, hormonal contraception modifies hormone levels and we don’t currently have much information about how the various types of birth control impact metabolism and performance.  The information in this post is related to women with regular menstrual cycles without hormonal contraception.

Estrogen and Metabolism

Out of all the female sex hormones, estrogen plays the biggest role in metabolism.  Metabolism is the breakdown of macronutrients (carbohydrates, protein, and fat) to produce energy.

Estrogen levels vary throughout the menstrual cycle, with levels peaking right before ovulation, then becoming elevated again about a week before menstruation.  The breakdown of different types of nutrients changes as estrogen levels fluctuate.

As indicated in the graph below, the luteal phase of the menstrual cycle is the roughly 2 weeks between ovulation and menstruation.  A rise in estrogen during this time is responsible for increasing how much fat is broken down for energy.  The result is that your body doesn’t need to rely as much on glucose to fuel exercise, so muscle glycogen (the storage form of glucose) is not depleted as quickly. (2)

Even though estrogen slows glycogen depletion during the luteal phase, during exercise or competition of longer than 2 hours, glycogen levels will eventually deplete.  Without sufficient carb intake, you may experience decreased performance in longer workouts/events during the luteal phase of the menstrual cycle. (2)

Estrogen is also believed to slow the breakdown of muscle proteins.  In studies conducted with post-menopausal women, higher levels of estrogen in the blood were associated with greater muscle mass and strength. (2)

Finally, in addition to the role it plays in metabolism, estrogen is an antioxidant. (3)  Antioxidants help to protect cells in the body from oxidative damage.  As such, estrogen helps to limit muscle damage during exercise, thereby limiting inflammation in the body as well. (2)

Progesterone and Metabolism

While progesterone doesn’t play as large a role in metabolism as estrogen, it is still very important and at times offsets the effects of estrogen.

Progesterone is believed to increase protein breakdown, particularly in the mid-luteal phase of the menstrual cycle when progesterone levels are elevated above estrogen levels. (1)  After ovulation, your body begins the process of thickening the uterine lining to support the fertilized egg.  Protein is required for this process, which explains the increased breakdown of protein throughout the body. (2)

Progesterone is also responsible for increasing core body temperature, skin temperature, and heart rate. (1) Progesterone further impairs body temperature regulation by increasing the temperature at which sweat begins. (2)  It is, therefore, very important to increase fluid intake during the luteal phase when progesterone levels are elevated, especially in hot and humid weather. 

How Do Female Hormones Impact Dietary Needs?

In general, women who have regular menstrual cycles can minimize the metabolic effects of hormones at different phases of the menstrual cycle by ensuring sufficient carbohydrate intake during prolonged exercise.  You should consume ~60 grams of carbs per hour of exercise. Carbohydrate intake during exercise minimizes glycogen depletion and protein breakdown. (1)

Follicular Phase

During the follicular phase of the menstrual cycle, when estrogen peaks and progesterone remains low, your body relies more on carbohydrates for fuel than it does during the luteal phase.  That said, it’s important not only to fuel with carbs both before exercise and during prolonged exercise, as mentioned above, but it’s also important to refuel with carbs as soon as possible following long (>60 minutes) or intense exercise to help recharge glycogen stores. (1)

Before exercise, you should aim for at least 1 gram of carbs per kilogram of body weight (0.5 g/lb) within a few hours of your workout.  As noted above, aim for ~60 grams per hour during longer workouts.

If carb loading during the follicular phase, you should increase carb intake to 8-10 grams per kilogram of body weight (3.6-4.5 g/lb) per day for the 3 days leading up to an event. (2)

Luteal Phase

During the luteal phase of the menstrual cycle, when both estrogen and progesterone are involved with metabolism, your body relies more on fat for fuel than it does during the follicular phase, and protein is broken down at a higher rate as well.  Impaired body temperature regulation and elevated heart rate during this phase also contribute to higher overall calorie needs. (2)

It is important to increase your protein intake during the luteal phase of your menstrual cycle.  Endurance athletes should consume no less than 1.63 grams of protein per kilogram of body weight (0.74 g/lb) during the follicular phase, so you should bump protein up a bit from your base during the luteal phase. (1)

Your body uses fat not only as a source of energy, but also for absorption of fat-soluble vitamins, protection of organs, production of hormones, and more.  Due to the higher utilization of fat for fuel in the luteal phase, you should also pay particular attention to ensuring that at least 20% of your calories come from fat during the luteal phase. (2) Be sure to include plenty of omega-3 fats from fish/seafood, nuts, seeds, and soy to help keep those hormones balanced.

Since carbohydrates spare protein from breakdown, you should also continue to ensure you get plenty of carbs during the luteal phase. 

In addition to increasing intake of protein, fat, and calories, you should pay close attention to hydration during the luteal phase, especially in hot and/or humid weather, to avoid overheating.

In Summary

Women with regular menstrual cycles who are not on hormonal contraception will have normal fluctuations in estrogen and progesterone levels throughout the menstrual cycle.  As estrogen and progesterone both impact metabolism of carbohydrates, protein, and fat in different ways, nutrition needs will change accordingly.

During the follicular phase of the menstrual cycle, which begins with the start of menstruation and ends at ovulation, estrogen rises to its highest level and progesterone remains low.  During this time, the body relies more on carbohydrates for energy.  As such, you should adjust carb intake to meet increased needs.

During the luteal phase of the menstrual cycle, which begins after ovulation and ends at menstruation, both estrogen and progesterone are elevated.  More fat is used for fuel during the luteal phase, and protein is broken down at a higher rate and used to prepare the body for pregnancy.  Body temperature regulation is also impaired during this phase.  You should increase protein, fat, and fluid intake during the luteal phase.  

Note, estrogen levels decline as we age, reaching almost negligible levels after menopause. (3)  This has multiple implications for metabolism, bone density, muscle retention, and more.  More women are staying active well beyond menopause these days, so a separate post dedicated solely to dietary adaptations during and after menopause is warranted.  Stay tuned!

Check out these posts on pre-workout fueling and protein absorption to learn more about how the body uses different nutrients and how to make sure you’re getting what you need.

If you need guidance with fueling for your menstrual cycle, I am available for 1:1 nutrition coaching.  Just send me a message to schedule a free informational call!

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