Women’s health practitioners have known for ages that body fat and energy stores affect reproduction. Women who don't have enough stored energy to sustain a pregnancy often have trouble ovulating or stop menstruating altogether. Changing weight is a challenge whether you are trying to lose or gain weight. However, the body needs a minimal amount of body fat for hormonal balance. It is important to determine the reasons why a person is underweight. Some of the reasons could be:

• genetics
• stress
• illness
• eating disorders.

A review of diet and lifestyle is the place to start. Underweight people are encouraged to eat every hour (the 100 calories every hour diet). If you can’t manage that, eat six times per day consistently every day. Drinking healthy caloric fluids is another good way to support weight gain as long as it doesn’t interfere with food eaten at meals.