German researchers took 25 sedentary women and observed the effects of dieting on their menstrual cycles. Of the women who lost more than two pounds per week, 10 developed disturbances in the luteal, or second, half of their cycles. Another five experienced impaired follicular development. A follicle is a sac within the ovary which houses the egg during its growth. One explanation for these changes is the decrease in the hormone, prolactin that occurred while these women were dieting. Lower prolactin was also correlated with decreased estrogen levels (6). All of these reproductive disturbances could compromise fertility.
Men are not excluded from the effects dieting has on fertility. Scientists at Boston's Massachusetts General Hospital recruited a group of overweight men to test the impact of fasting on reproductive function. After these men fasted for six to seven days, their plasma testosterone fell by one-third. This hormone returned to its original level once the men began eating normally for several days. The researchers speculated that fasting has a direct impact on men's testicles. Lack of food, they think, may inhibit hormone formation or reduce a testicle's response to hormones (7).
3. Timing is Everything
Animals display distinct seasonal changes in their reproductive abilities. Interestingly, the same is true for people. Although the seasons have a minimal impact on modern societal activities, our bodies still respond to changes in the seasons. It is well documented that men's semen quality and count varies throughout the year reaching its peak as winter ends and spring begins (February to March). A British study illustrated a similar trend in women. Several women were seen at Jessop Hospital in Sheffield for artificial insemination. This is important to mention because it clarifies that frequency of intercourse and rate of ovulation did not influence conception. Researchers found that conception, using insemination, was more common from early winter to early spring (October to March). The most fruitful month was November.
Although investigators couldn't offer a concrete reason why this was so, they said it is possible that the pituitary or pineal glands are more active during these times. The endometrial layer lining the uterus may also be more receptive during winter. Or it may be that, for some unknown reason, a woman's eggs are more fertile in November (8).
These findings should not surprise anyone. Nature is cyclical. Not only does a woman's fertility peak during a particular period each year, but also at a specific time each month. The egg lives a short 24 hours during a menstrual cycle. Using natural family planning methods to observe and chart cervical mucus, basal body temperature and other fertility signs, a couple can pinpoint when conception will most likely occur.
- Zavos PM. Cigarette smoking and human reproduction: effects on female and male fecundity. Infertility 1989;12: 35-46.
- Rosevear SK et al. Smoking and decreased fertilisation rates in vitro. The Lancet 1992; 340: 1195-96.
- Van Voorhis BJ, Syrop CH, Hammitt DG, Dunn, MS, Snyder GD. Effects of smoking on ovulation induction for assisted reproductive techniques. Fertility and Sterility. 1992; 58(5): 981-85.
- Dawson EB, Harris WA, Teter MC, Powell, LC. Effect of ascorbic acid supplementation on the sperm quality of smokers. Fertility and Sterility 1992; 58(5): 1034-39.
- British Medical Journal 1993; 306:484-7.
- Pirke KM, Tuschl RJ. Prolactin concentrations during menstrual cycles disturbed by weight reducing diets or exercise. Infertility 1988; 11: 185-192.
- Kyung NH et al. Effect of carbohydrate supplementation on reproductive hormones during fasting in men. Journal of Clinical Endocrinology and Metabolism. 1985; 60(5): 827-35.
- Paraskevaides EC, Pennington GW, Naik S. Seasonal distribution in conceptions achieved by artificial insemination by donor. British Medical Journal 1988; 297: 1309-10.