Research suggests exercising too much, being too lean
can create fertility problems


Most know that if you are so lean and/or exercising so much that you don't get your period you won't conceive a child. (This is called amenorrhea.) Few people discuss what else is on this continuum when energy availability is low: luteal phase deficiency, follicular development disturbances, and anovulatory cycles.

Depending on your genes, leading an athletic lifestyle may actually decrease your fertility.

You will still get your period, but your egg, hormone levels, and/or lining may suffer.

For those of you who have worked hard for your figure, this may be unwelcome news. Good habits are just as hard to break as bad ones. So see for yourself. Studies supporting the recommendation to reduce exercise when trying to conceive:

Luteal Phase Deficiency in Recreational Runners: Evidence for a Hypometabolic State

Mary Jane de Souza, Jaci Van Heest, Laurence M. Demers and Bill L. Lasley. Women's Exercise and Bone Health Laboratory (M.J.D.S., J.V.H.), Faculty of Physical Education and Health, University of Toronto, Toronto, Ontario, Canada M5S 2W6; Department of Kinesiology (J.V.H.), University of Connecticut, Storrs, Connecticut 06269; Penn State University (L.M.D.), Milton S. Hershey Medical Center, Hershey, Pennsylvania 17033; and Institute of Toxicology and Environmental Health (B.L.L.), University of California, Davis, California 95616

"Menstrual cycle disturbances have been described previously as existing along a spectrum or continuum of reproductive disorders, ranging from ovulatory cycles and subtle luteal phase deficiency (LPD) to overt amenorrhea. The possibility that the same woman may express many of these disturbances intermittently may be more common than previously realized. Modulation of an individual's position on this continuum is essentially affected by caloric intake and caloric expenditure; that is, energy balance. As the data by De Souza et al. suggest, exercising women who exhibit mild to moderate menstrual cycle abnormalities revert back and forth from ovulatory cycles, LPD cycles, and anovulation rather frequently and intermittently, and this is probably modulated by changes in energy balance. The LPD women described in this study are most likely in a transitional state in their metabolic and endocrine physiology whereby their metabolic hormonal balance is less homeostatic than in those individuals who are either consistently ovulatory or consistently amenorrheic. It is therefore probable that these exercising women with LPD are in a state of intermittent short-term negative energy balance and are likely adapting to unfavorable combinations of dietary intake and physical exercise that lead to compromised luteal function."

Full Article from The Journal of Clinical Endocrinology & Metabolism 88(1):337-346

The effects of intense exercise on the female reproductive system

M P Warren and N E Perlroth. Department of Obstetrics and Gynecology, Columbia College of Physicians and Surgeons, New York, New York, USA

The incidence of inadequate luteal phase, anovulation and oligomenorrhea is considerably greater in athletes than non-athletes (Petterson et al. 1973, Vollman 1977, Frisch et al. 1981, Singh 1981, Highet 1989). The exact incidence of these abnormalities is unknown, however, as many 'eumenorrheic' athletes are actually suffering from hidden menstrual irregularities such as inadequate luteal phase or anovulatory cycles (Shangold et al. 1979, Bonen et al. 1981, Prior et al. 1982, Loucks et al. 1989). Dale et al. (1979) found that only 50% of runners ovulated during a test month compared with 83% of controls. The incidence of infertility associated with these problems may also be greater than suspected." "Often a weight gain of 1-2 kg or a 10% decrease in exercise load (in either duration or intensity) is sufficient to reverse reproductive dysfunction (Prior & Vigna 1985, Drinkwater et al. 1986).

Full Article from Journal of Endocrinology (2001) 170, 3-11

What's in a Name? In Search of Leptin's Physiologic Role

Jeffrey S. Flier Department of Medicine, Division of Endocrinology, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215

"...rising levels of leptin signal the brain (and possibly other sites) that excess energy is being stored (in the form of fat), and this signal brings about adaptations that resist obesity. When this signal is deficient, the brain perceives energy stores to be insufficient, and the physiological response is to increase appetite and decrease energy expenditure, both of which push energy balance towards energy storage and weight gain." "It was shown that leptin levels fall fairly rapidly (i.e. within hours) with energy deprivation in rodents (18, 19), and they do so (initially) out of proportion to the loss of fat stores. This suggests that, in addition to being a readout of energy stores, the leptin level is a sensor of energy balance or the relationship of energy intake to expenditure at a point in time. Next, a classic replacement strategy was employed to show that starvation-induced changes in neuroendocrine status were blunted or prevented entirely when a starved animal was replete with leptin. Thus, the activation of the hypothalamic-pituitary-adrenal (HPA) axis, and suppression of the thyroid and reproductive axes, were blunted or prevented by leptin repletion during starvation in rodents, establishing that these effects are signaled, at least in part, by the fall in leptin."

Full Article from Journal of Clinical Endocrinology and Metabolism Vol. 83, No. 5, 1407-1413

High frequency of luteal phase deficiency and anovulation in recreational women runners: blunted elevation in follicle-stimulating hormone observed during luteal-follicular transition.

De Souza MJ, Miller BE, Loucks AB, Luciano AA, Pescatello LS, Campbell CG, Lasley BL. Center for Fertility and Reproductive Endocrinology, New Britain General Hospital, Connecticut 06050, USA.

The purposes of this investigation were to evaluate the characteristics of three consecutive menstrual cycles and to determine the frequency of luteal phase deficiency (LPD) and anovulation in a sample of sedentary and moderately exercising, regularly menstruating women. For three consecutive menstrual cycles, subjects collected daily urine samples for analysis of FSH, estrone conjugates (E1C), pregnanediol-3-glucuronide (PdG), and creatinine (Cr). Sedentary (n=11) and exercising (n=24) groups were similar in age (27.0+/-1.3 yr), weight (60.3+/-3.1 kg), gynecological age (13.8+/-1.2 yr), and menstrual cycle length (28.3+/-0.8 days). Menstrual cycles were classified by endocrine data as ovulatory, LPD, or anovulatory. No sedentary women (0%) had inconsistent menstrual cycle classifications from cycle to cycle, but 46% of the exercising women were inconsistent. The sample prevalence of LPD in the exercising women was 48%, and the 3-month sample incidence was 79%. In the sedentary women, 90% of all menstrual cycles were ovulatory (SedOvul; n=28), whereas in the exercising women only 45% were ovulatory (ExOvul; n=30); 43% were LPD (ExLPD; n=28), and 12% were anovulatory (ExAnov; n=8). In ExLPD cycles, the follicular phase was significantly longer (17.9+/-0.7 days), and the luteal phase was significantly shorter (8.2+/-0.5 days) compared to ExOvul (14.8+/-0.9 and 12.9+/-0.3 days) and SedOvul (15.9+/-0.6 and 12.9+/-0.4 days) cycles. Luteal phase PdG excretion was lower (P < 0.001) in ExLPD (2.9+/-0.3 microg/mg Cr) and ExAnov (0.8+/-0.1 microg/mg Cr) cycles compared to SedOvul cycles (5.0+/-0.4 microg/mg Cr). ExOvul cycles also had less (P < 0.01) PdG excretion during the luteal phase (3.7+/-0.3 microg/mg Cr) than the SedOvul cycles. E1C excretion during follicular phase days 2-5 was lower (P=0.05) in ExOvul, ExLPD, and ExAnov cycles compared to SedOvul cycles and remained lower (P < 0.02) in the ExLPD and ExAnov cycles during days 6-12. The elevation in FSH during the luteal-follicular transition was lower (P < 0.007) in ExLPD (0.7+/-0.1 ng/mg Cr) cycles compared to SedOvul and ExOvul cycles (1.0+/-0.1 and 1.1+/-0.1 ng/mg Cr, respectively). Energy balance and energy availability were lower (P < 0.05) in ExAnov cycles than in other menstrual cycle categories. The blunted elevation in FSH during the luteal-follicular transition in exercising women with LPD may explain their lower follicular estradiol levels. These alterations in FSH may act in concert with disrupted LH pulsatility as a primary and proximate factor in the high frequency of luteal phase and ovulatory disturbances in regularly menstruating, exercising women.

Full Article from Journal of Clinical Endocrinology and Metabolism, Vol. 83, No. 12, 4220-4232

Effects of short-term strenuous endurance exercise upon corpus luteum function.

Med Sci Sports Exerc. 1999 Jul;31(7):949-58. Williams NI, Bullen BA, McArthur JW, Skrinar GS, Turnbull BA. Department of Health Sciences, Sargent College, Boston University, MA, USA. niw1@psu.edu

PURPOSE: The present study tested whether short-term, abruptly initiated training can cause corpus luteum dysfunction when exercise is limited to either the follicular or luteal phase of the cycle. METHODS: Reproductive hormone excretion and menstrual characteristics were studied in sedentary women who exercised only during the follicular (N = 5) or the luteal (N = 4) phase. Six women served as controls, three of whom exercised at a low volume and three who remained sedentary. Weekly progressive increments in exercise volume continued until either ovulation (follicular group) or menses (luteal group) occurred. Physical activity and nutrient intake were closely monitored with the intent to maintain body weight. RESULTS: No luteal phase disturbances occurred in any of the control subjects, whereas 40% of follicular and 50% of luteal exercisers experienced luteal defects. The proportion of menstrual cycles disrupted was not different between luteal and follicular exercisers (50% vs 30%, respectively) but was significantly greater than the proportion of cycles disrupted in control subjects (P < 0.05). CONCLUSIONS: These results suggest that exposure to abrupt onset of training can alter luteal function, regardless of the menstrual cycle phase in which exercise occurs. This study also demonstrates that a relatively low volume of exercise suffices to induce mild disturbances in luteal function.

PMID 10416555

Physical exercise and menstrual cycle alterations. What are the mechanisms?

Sports Med. 1990 Oct;10(4):218-35. Keizer HA, Rogol AD. Department of Physiology, University of Limburg, Maastricht, The Netherlands.

The prevalence of menstrual cycle alterations in athletes is considerably higher than in sedentary controls. There appears to be a multicausal aetiology, which makes it extremely difficult to dissociate the effects of physical exercise on the menstrual cycle from the other predisposing factors. From cross-sectional studies it appeared that physical training eventually might lead to shortening of the luteal phase and secondary amenorrhoea. Prospective studies in both trained and previously untrained women have shown that the amount and/or the intensity of exercise has to exceed a certain limit in order to elicit this phenomenon. We hypothesise, therefore, that apart from a certain predisposition, athletes with a training-induced altered menstrual cycle are overreached (short term overtraining, which is reversible in days to weeks after training reduction). Menstrual cycle alterations are most likely caused by subtle changes in the episodic secretion pattern of luteinising hormone (LH) as have been found in sedentary women with hypothalamic amenorrhoea as well as in athletes after very demanding training. The altered LH secretion then, might be caused by an increased corticotrophin-releasing hormone (CRH) secretion which inhibits the gonadotrophin-releasing hormone (GnRH) release. In addition, increased CRH tone will lead to increased beta-endorphin levels which will also inhibit the GnRH signaller. Finally, the continuous activation of the adrenals will result in a higher catecholamine production, which may be converted to catecholestrogens. These compounds are known to be potent inhibitors of GnRH secretion. In conclusion, menstrual cycle alterations are likely to occur after very demanding training, which causes an increase secretion of antireproductive hormones. These hormones can inhibit the normal pulsatile secretion pattern of the gonadotrophins.

PMID 2247724

Induction of menstrual disorders by strenuous exercise in untrained women.

N Engl J Med. 1985 May 23;312(21):1349-53.Bullen BA, Skrinar GS, Beitins IZ, von Mering G, Turnbull BA, McArthur JW.

We performed a prospective study of 28 initially untrained college women with documented ovulation and luteal adequacy to determine whether strenuous exercise spanning two menstrual cycles would induce menstrual disorders. To ascertain the influence, if any, that weight loss might exert, we randomly assigned the subjects to weight-loss and weight-maintenance groups. Subjects were expected to run 4 miles (6.4 km) per day, progressing to 10 miles (16.1 km) per day by the fifth week, and to engage daily in 3 1/2 hours of moderate-intensity sports. The normalcy of the menstrual cycles during the period of exercise was judged independently according to clinical and hormonal criteria, the latter comprising serial measurements of gonadotropin and sex-steroid excretion. A higher percentage of abnormalities proved to be detectable by hormonal means (P less than 0.02). Only four subjects (three in the weight-maintenance group) had a normal menstrual cycle during training. In the weight-loss group, the number of women who had luteal abnormalities as compared with those who lost the surge in luteinizing hormone altered significantly over time, the latter occurring more frequently (P less than 0.01) as training progressed. Within six months of termination of the study, all subjects were again experiencing normal menstrual cycles. We conclude that vigorous exercise, particularly if compounded by weight loss, can reversibly disturb reproductive function in women.

PMID 3990734

Fertile Panda note: If you put your body under physical stress (as you do on purpose with exercise), it may think, "With all these demands, now is not the time to bear children." This reaction may have served a purpose for our ancestors when food scarcity was a real risk and failed pregnancies could be fatal. Now however, it's an unfortunate clash with our modern concept of beauty.


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