Nutrition for Female Runners & Sex Differences in Athletics

By Holley Samuel MEd, RD, LD, CSSD, CPT


Introduction

We live in a world where women make up ~57% of the finishers crossing the line at races. There’s been a ~25% increase in female participation in running in the past few years, and we are totally here for it! That being said, despite a rise in female participation in athletics, most current sports nutrition and performance research has historically been completed in cis-male populations. New research is starting to be completed on cis-female athletes, which should help make nutrition and exercise recommendations for cis women in sport more specific and relevant, as present sex differences in physiology make previous cis-male findings in research potentially not applicable to cis-females. More research needs to be done on trans gender athletes to have a better understanding of specific nutrition and performance implications in this population. 

Ladies, do you find that you respond differently to certain diets, types of workouts, or supplements than other males in your life? Maybe you find that you and your male peers could do the same diet and workout program and get completely different results. There’s reasons for this- as researchers in the field like Dr. Stacy Sims- have coined, “women are not small men.” So perhaps, we should not be training and fueling like we are! Historically, most sports research was conducted on young male athletes and applied to all genders and age athletes across the board. This is not necessarily appropriate or applicable to every athletic population. Women have many physiological differences than men, and one of the driving factors of this is the menstrual cycle. Women ARE still human beings though… so many scientific concepts that we’ve extrapolated from male data do still apply to women to some degree too.

In this article, we will dive into current nutrition recommendations for cis-female runners who are pre-menopausal from a performance and health standpoint, and how they differ from traditional cis-male centered recommendations. 

First, let’s observe a brief review of the menstrual cycle.



The menstrual cycle has 2 main phases and is generally 28 days long on average (but can range anywhere between 21-40 days normally). The follicular, or “low hormone” phase occurs at the start of a woman’s period through ovulation, which is usually around 14-18 days in most women. The luteal, or “high hormone” phase starts after ovulation up until the start of a woman’s period.

Hormonal fluctuations throughout the cycle have effects on females’ abilities to use macronutrients (fat, protein, and carbohydrate are the macronutrients that provide the body with calories) and is the root of why nutrition recommendations differ between men and women. Approximately 64.9% of women who are between the ages of 15-49 in the USA are currently taking hormonal contraceptives, which further alters nutrition recommendations based on that individual and what type of contraceptive they use. Men do not have a monthly hormone cycle, and therefore have the ability to remain more consistent and constant throughout the month in their abilities to use and metabolize these macronutrients. We will discuss how nutrition recommendations differ within each phase of the menstrual cycle below.


Energy & Macronutrient Needs


One important thing to note, is that historically females tend to under-eat and also have more of a desire to be thin than men. While we won’t go too much into the nuance of why this is the case in terms of societal standards, diet culture pressures, and eating disorder prevalence, it is important to identify if you are meeting your caloric needs in the first place prior to implementing other sex specific nutrition strategies. When we do not meet our calorie needs (either intentionally or unintentionally), this can cause negative consequences such as: hormone imbalances, menstruation changes, osteoporosis or osteopenia, poor performance, and increased risk for injury or burnout among many other complications.


How to know if you are meeting your needs? 40-45 calories per kg of fat-free mass (lean body mass) per day is recommended to maintain energy balance in an active population. This range meets the bare minimum, and chances are if you want to improve your performance, you’ll likely need to eat even more. Also to note, most women will experience a 2.5–11.5% higher resting energy expenditure (REE) during the luteal phase of the menstrual cycle. Menstruating individuals, have you ever experienced increased hunger during certain times of the month (read: the week or two before your period starts) and wondered why you feel that way? It’s your body trying to tell you something- it needs more food this week(s) in order to perform its best! 

Carbohydrates

Macronutrients, or “macros,” provide the body with calories, or “energy.” The macronutrient that should make up the majority of an endurance athlete’s (whether male or female) diet is carbohydrates. For females in endurance sports like running, it is recommended that they consume 45-65% of their total daily calories from carbohydrates, or 6-10g per kg body weight per day of carbohydrates. 

So if you’re a 150lb female (68.1kg), that’s between 409-681g carbohydrates per day (150lb/2.2=68.1 kg x 6-10= 409-681g carbs/day). Many females are not meeting their carbohydrate needs and therefore are not meeting their calorie needs in order to optimize their health and performance as runners. Carbohydrates are used more efficiently by the body during the follicular phase of the menstrual cycle and are stored more efficiently during the luteal phase in cycling females. Many women in menopause also experience inefficient use of carbohydrates and poor access to the carbohydrates they do store, which makes the timing of carbohydrates around exercise an important key to consider. No matter what your “access” level is to the carbohydrates you eat or store in the body as glycogen, the key takeaway here is that you still require 45-65% of your total calorie needs from carbohydrates as a female endurance athlete. 

Recent research also supports the recommendation of 30-60g carbohydrates per hour during long runs (long runs are anything over 75-90 minutes long) no matter what phase of the menstrual cycle you’re in. 1-4g/kg bodyweight carbohydrate in the 1-4 hours before your training or competition and 0.75g/kg bodyweight carbohydrate immediately after exercise to restore muscle glycogen stores and promote optimized recovery are also recommended for female athletes throughout the cycle. 

For distances over 2 hours, current research on men shows 60-120g carbs will benefit performance, but we don’t have research on these higher carbohydrate intake levels yet for female athletes- so if you take in more carbs during longer runs and feel good doing so as a female athlete, go along with what works best for your individual needs.

Recent research also supports that females can and should carbo-load prior to competitions or long runs with 8-10g/kg bodyweight carbohydrate per day in the 3 days or so prior to their competition. Older research showing that carb loading does not benefit women is flawed, in that the women in the studies concluding this were not consuming enough carbohydrate to appropriately carb load in the first place in comparison to what’s recommended to their male counterparts. If anything, this research pointed out that females are more susceptible to underfueling. Women can and SHOULD carb load.


Protein

Protein is a key player in recovery and maintenance of lean body mass in both males and females, but is especially important for females, who tend to have less lean body mass than males (generally speaking). Female runners need between 1.6-1.8g/kg bodyweight protein daily in order to optimize recovery, body composition, and metabolism. For the 150lb female (68kg), that’s between 109-123g of protein per day. Women may need more if they are also incorporating strength based exercise.

Women experience more potential muscle breakdown during the luteal phase of their cycles and peri and post menopause, so athletic women in these categories may benefit from focusing on consuming adequate protein. The best results to stimulate muscle growth (read: looking “toned”) in women were found when protein was incorporated in every meal and snack spread across the day in 20g doses every 4 hours, however women in menopause may need 40g protein post workout to stimulate the same result.

Fat

The current recommended macronutrient distribution range for fat is between 20-35% of calories for both men and women with at least 15% of that range preferably coming from unsaturated fat sources like nuts, seeds, fish, avocado, olive oil, lean meats, eggs, and other non inflammatory sources.


Takeaways

So what to do with all of this information? 

  • Track your cycle and take note of any changes in your appetite or energy levels you may be feeling. Also note any irregularities in your cycle and discuss with your coach, doctor, and registered dietitian.

  • Make note of when your goal races are during your cycle & adjust your fueling strategy as needed.

  • Know that your hormonal contraceptive may be masking symptoms that arise from inadequate nutrition and may negatively impact your performance, so talk with your registered dietitian and doctor about what considerations you should make based off your individual needs and preferences .

  • Consume 40-45 or more calories per kilogram of fat-free mass, 45-65% of your total calories from carbs, 20-35% of your calories from fat, and 1.6-2.0g per kilogram bodyweight from protein to support your training throughout the cycle

    • Focus on increasing your calorie intake by 2.5-11.5% and emphasizing fiber, fat, and protein intake during your luteal phase (the 1-2 weeks before your period after ovulation) or simply eating more by paying attention to increased hunger cues

    • Emphasize carbohydrate intake and preferably plan harder training efforts during your menstrual & follicular phases (the week of and after your period) or use rate of perceived exertion (RPE) throughout your cycle instead of strict paces

  • Check out the Holley Fueled Nutrition podcast episodes as a further resource

Know that you can perform well on any day throughout your cycle as long as you use these tools to adjust your nutrition and training strategy!

About Holley Samuel

References

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Holley Samuel