Extreme dieting and eating disorder can leave women infertile at an early age, health experts caution.
The normal warning sign that a woman's fertility is being affected is when her periods stop.
"The hypothalamus in the brain controls the release of hormones from the pituitary gland that drives the menstrual cycle, stimulating the ovaries to produce eggs," the Daily Mail quoted Dr Marie Wren, deputy medical director of the Lister Fertility clinic in London, as saying.
"But if a woman loses a lot of weight, this process shuts down. It's the body's way of preserving what resources it has. If a woman menstruates, she loses iron - and if she has little nutritional input, she can't afford to lose that," she stated.
Bulimia, an eating disorder when person binge eats and purges food through vomiting or laxatives, and faddy yo-yo dieting can also trigger this process.
"If your body weight is yo-yoing, then it is possible your body would perceive this as a stress and so switch off the ovulation mechanism," explained Amanda Tozer, consultant in reproductive medicine at Barts and the London Hospital.
"If you are just losing a few pounds either way you'll probably be fine, but if your weight is really going from one extreme to another than this may happen," she added.
Following low-calorie restrictive diets may also compromise a woman's chance of getting pregnant.
"If you aren't getting enough nutrients, then your body will not function as normal and this will reduce fertility," said Dr Wren.
The worst thing is that the effects cannot be reversed.
About 20 percent of those who become seriously underweight find their menstrual cycle never returns, even when they are at healthy weight.
"It is not just a woman's fertility that is affected by weight. An underweight man will have poorer quality sperm as he is undernourished, likewise if he is overweight," Dr Wren explained.
"One study found that men with a high BMI ejaculate less sperm and more of them are abnormally shaped than normal," she added.