Some physically active women are at risk for a group of symptoms called the Female Athlete Triad. This often unrecognized disorder is a combination of three conditions:
Low energy availability (inadequate caloric intake); with or without disordered eating
Amenorrhea (lack of menstrual periods)
Low bone mineral density
It's important to know that in the context of Female Athlete Triad, disordered eating includes both intentional and non-intentional under-consumption of calories. This can occur both as a function of poor eating habits and as a function of too intense exercise. When the body perceives too great a gap between energy expenditure and energy intake, estrogen levels in the body drop and menstrual periods cease. Normal estrogen levels are needed to maintain calcium content in bone. The result of lower estrogen is that the bones become progressively more porous, resulting in ostopenia, and eventually, osteoporosis.