Reproductive Consequences of Underfueling

by Nicole Strock PhD (ABD), Theresa Cwenar & Maddie Holmberg, Mary Jane De Souza PhD

July 2020

Manipulating weight for competitions is a commonly accepted social norm in the world of combat sports. As athletes, you are raised with “whatever it takes” mindset and “no pain no gain” attitude. These tools can lead to great success, but where can they become harmful? The answer is clear: when you jeopardize your health. You cannot reach peak performance if you are not healthy enough to train. As an athlete, it is important to understand that an inadequate energy intake may lead to impaired health and impaired performance. When you are not consuming enough calories each day to meet the needs for your level of physical activity, your body begins to alter important systems. When you are properly fueling and utilizing food as a tool to supplement your training, you will be better prepared and have the energy to pursue your short- and long-term goals.

As women who fight, it is essential to fuel your body so that you have enough energy for every round. Because many combat sports involve weight-cycling, this puts you at higher risk for being in a state of energy deficiency–this occurs when you do not have enough energy for your body’s needs or exercise. An energy deficiency will not allow you to feel your best throughout a training session or throughout the day, and we will explain how it can lead to a chain reaction of other health complications. The most important idea to keep in mind is to focus on how your body feels, and not how it looks in the mirror. As women in combat sports, we cannot deny that the number on the scale is important, however, it is crucial that you are competing at a weight that supports your health and are achieving this weight in a healthful way.  

You might be wondering, what can happen to your body if you are chronically energy deficient or underfueled? When you are consistently depriving yourself of adequate fueling to support practice and competition, you put yourself at risk to develop physiological consequences of The Female Athlete Triad (Triad), a condition encompassing the metabolic and reproductive dysfunction stemming from a chronic energy deficit that contributes to poor bone health [1]. Almost four decades of rigorous scientific research have investigated the energy-reproduction-bone paradigm, i.e., the Female Athlete Triad and it has recently been used as the evidence-based cornerstone of the more recently introduced model of Relative Energy Deficiency in Sport (RED-S) [2, 3]. Simply put, when you aren’t eating enough to support high training loads, your metabolism slows down and you might experience a range of menstrual cycle disturbances. Essentially, your body has complex mechanisms to sense and communicate energetic status to various tissues and organs throughout the body- one key regulator is the hypothalamus-pituitary-ovarian axis. During times of energy deficiency, the “communication,” indicated by the release of hormones, between the hypothalamus and pituitary gland is lessened, which ultimately impacts the release of other hormones controlling reproductive function [4, 5]. When underfueling has occurred for an extended period of time, you could experience a severe reproductive dysfunction called amenorrhea, or the lack of a menstrual period for three or more months. This can have serious implications for your bone health, because when you are not regularly menstruating, you are not producing enough estrogen—estrogen is incredibly important for bone health by helping to prevent the breakdown of bone and the occurrence of bone stress injuries. 

“no pain no gain” attitude
Photo by: Nigel Lough


1. De Souza, M.J., et al., 2014 Female Athlete Triad Coalition Consensus Statement on Treatment and Return to Play of the Female Athlete Triad: 1st International Conference held in San Francisco, California, May 2012 and 2nd International Conference held in Indianapolis, Indiana, May 2013. Br J Sports Med, 2014. 48(4): p. 289.

2. Williams, N.I., et al., Female Athlete Triad and Relative Energy Deficiency in Sport: A Focus on Scientific Rigor. Exerc Sport Sci Rev, 2019. 47(4): p. 197-205.

3. De Souza, M.J., et al., Current Status of the Female Athlete Triad: Update and Future Directions. Curr Osteoporos Rep, 2017. 15: p. 577-587.

4. Loucks, A.B., M. Verdun, and E.M. Heath, Low energy availability, not stress of exercise, alters LH pulsatility in exercising women. J Appl Physiol (1985), 1998. 84(1): p. 37-46.

5. Koltun, K.J., et al., Energy Availability Is Associated With Luteinizing Hormone Pulse Frequency and Induction of Luteal Phase Defects. J Clin Endocrinol Metab, 2020. 105(1).

6. De Souza, M.J., et al., High prevalence of subtle and severe menstrual disturbances in exercising women: confirmation using daily hormone measures. Hum Reprod, 2010. 25(2): p. 491-503.

7. De Souza, M.J., et al., High frequency of luteal phase deficiency and anovulation in recreational women runners: blunted elevation in follicle-stimulating hormone observed during luteal-follicular transition. J Clin Endocrinol Metab, 1998. 83(12): p. 4220-32.

8. Rouveix, M., et al., Eating attitudes, body esteem, perfectionism and anxiety of judo athletes and nonathletes. Int J Sports Med, 2007. 28(4): p. 340-5.

9. Trutschnigg, B., et al., Female boxers have high bone mineral density despite low body fat mass, high energy expenditure, and a high incidence of oligomenorrhea. Appl Physiol Nutr Metab, 2008. 33(5): p. 863-9.

10. Degoutte, F., et al., Food restriction, performance, biochemical, psychological, and endocrine changes in judo athletes. Int J Sports Med, 2006. 27(1): p. 9-18.

11. Koehler, K., et al., Low energy availability in exercising men is associated with reduced leptin and insulin but not with changes in other metabolic hormones. J Sports Sci, 2016. 34(20): p. 1921-9.

12. De Souza, M.J., et al., Gonadal hormones and semen quality in male runners. A volume threshold effect of endurance training. Int J Sports Med, 1994. 15(7): p. 383-91.

13. Barrack, M.T., et al., Evidence of a cumulative effect for risk factors predicting low bone mass among male adolescent athletes. Br J Sports Med, 2017. 51(3): p. 200-205.

14. Kraus, E., et al., Bone stress injuries in male distance runners: higher modified Female Athlete Triad Cumulative Risk Assessment scores predict increased rates of injury. Br J Sports Med, 2018.

15. Tenforde, A.S., et al., Parallels with the Female Athlete Triad in Male Athletes. Sports Med, 2016. 46(2): p. 171-82.

16. De Souza, M.J., K.J. Koltun, and N.I. Williams, The Role of Energy Availability in Reproductive Function in the Female Athlete Triad and Extension of its Effects to Men: An Initial Working Model of a Similar Syndrome in Male Athletes. Sports Med, 2019. 49(Suppl 2): p. 125-137.