Scientists have long noticed the effects of famine on nations afflicted with starvation over long periods of time. The population growth slows to a crawl and then stops. If the famine isn't too lengthy, the birth rate takes off once the food supply is restored. Nature knows how to catch up with itself.
This phenomenon was seen in Bengal in 1943, in China during the years 1958-1961, and in Ethiopia from1983-1985. The population growth grinded to a halt during the famine but began to boom again within a few years after.
More curious perhaps is the fact that the effects of famine are being observed in modern populations where food is plentiful. One University of Pittsburgh study has demonstrated that working out is the citified equivalent of starvation. Women who go in for strenuous workouts are finding the act of conception to be mission impossible. So, what's the link between famine and having that workout in a fancy gym? It's simple: when it comes to fertility, calories count.
The Pittsburgh researchers used monkeys to show that workouts can lead to infertility. The monkeys were given marathon training-level workouts. The scientists observed that as the level of exercise increased, but calorie intake remained stable, the monkeys ceased to menstruate.
When the monkeys' caloric intake was increased to between 31-81% more calories, even though the energy expended during training remained the same, normal menstrual cycles returned. It was seen that monkeys fed the greatest amounts of food got back their normal menstrual periods that much sooner.
But back to humans: what happens when women don't eat enough? The hypothalamus, located in the brain, signals the body to halt ovulation and menstruation. The body has concluded that it is not being fed enough calories to support a pregnancy. The medical director of Midlands Fertility Services in the U.K., Dr. Diane Lockwood, has stated, "Women who are very thin have higher risks of miscarriage and babies born prematurely. There is overwhelming evidence that thin women have underweight babies."
But how can a woman judge how thin is too thin? It's simple: don't let your body mass index (BMI) fall lower than 19. The National Institute of Clinical Excellence has issued guidelines suggesting that women who wish to undergo fertility treatments need to have a BMI of between 19 and 30. That's because being overweight or underweight tends to make fertility treatment less than successful.
A woman who has gone overboard with exercise or diet and whose periods have stopped may sometimes find it hard to get back to normal without medical intervention. In this case, prescription medications are useful in giving things in the fertility department a jump-start.