If you’re cutting calories while logging long rides or runs, you could be damaging your body, according to a new study in Medicine & Science in Sports & Exercise. According to the study's authors, active women who limit calories may increase their risk of menstrual problems and osteoporosis.
The symptoms are part of the Female Athlete Triad, a syndrome that comprises three issues: eating disorder, loss of bone mineral density and the absence of a menstrual period.
The new article is just one part of a study at Pennsylvania State University to understand the effects of increased caloric intake on menstrual and bone health in active women with menstrual disturbances over a year.
The study is the first to consider the relationship between calorie consumption and energy availability in active women. In this case, energy refers to the amount of fuel one's body has available to function. When you don’t eat enough, your body saves its limited fuel for vital operations such as body-temperature regulation. Because women don’t need a menstrual cycle to survive, this function slows or shuts down completely when resources are scarce. This interruption can have adverse effects on estrogen levels and bone health.
Because energy availability is an indicator for health risks, researchers wanted to know how calorie restriction affects energy availability in women. They tracked the food and exercise logs of 87 participants and also put the women through a series of lab tests to measure energy and menstrual cycle hormones.
The findings concluded that more research is needed to understand a correlation. While women who ate less (about 1,600 calories per day) had lower energy availability and a higher frequency of menstrual problems, women who consumed 1,900 calories per day and who had higher energy availability still had menstrual issues.
According to study author Mary Jane De Souza, Ph.D., a physiology professor at Penn State, the finding suggests the "energy-availability" threshold that puts women at risk for health complications could be higher than her team originally believed. It could also suggest, she said, that energy availability differs between active women and inactive women.
Further studies are also needed to understand how long it takes a woman with low energy availability to develop menstrual abnormalities and other health issues.