Kaleigh Camp, M.S.
What is “reduced energy availability”? “Energy availability” refers to the post-exercise energy that can be used for metabolic processes (energy intake minus exercise energy expenditure). Reduced energy availability can actually approach deficit due to a low caloric intake, a vigorous exercise regimen, or both. The condition is often but not necessarily associated with eating disorders, with inherently higher risk for female athletes. The relationship between low energy availability, irregular menstrual functions, and decreased bone mineral density is referred to as the female athlete triad. Low energy availability can cause menstrual disturbances and disruptions in bone integrity. The triad operates on a continuous spectrum from healthy to diseased states. Small disruptions can causes changes in athletic performance by causing fatigue and a need for an increased recovery period between training sessions, while greater disturbances can cause disorders like functional hypothalamic amenorrhea (an abnormal menstrual cycle that is induced by low energy through the alterations of endocrine factors including leptin, IGF-1, and T3) and bone loss which can lead to osteoporosis. Obviously, behavior can control energy intake and output, potentially leading to restoration of a normal menstrual cycle. The important question is whether an athlete’s bone density can fully recover after a period of adequate nutrition and eumenorrhea (normal 
menstrual cycles occurring at a 28 day interval) or does the triad cause irreversible damage?
Potentially irreversible bone damage can occur, depending on an athlete’s history of disordered eating and menstrual status. This especially occurs in amenorrheic athletes, those who lack a menstrual cycle for more than 90 days. Bone mineral density decreases as the duration of abnormal menstrual cycles increases. Many research studies suggest that this loss in bone mineral density cannot be fully recovered even after those factors return to normal. Even with additional pharmacological treatments like hormone replacements and bisphosphonates, it is difficult to restore peak bone mass. Peak bone mass can predict bone loss after menopause. If an individual does not attain peak bone mass due to disturbances in factors such as diet, exercise and hormones early in life, there will be less bone to lose during age-related bone loss. This could potentially lead to increased fracture risk and even osteoporosis, which is defined by the NIH as “a skeletal disorder characterized by comprised bone strength predisposing a person to an increased risk of fracture”.
Due to the concern that even after a recovery period some athletes will not fully recover from decreased bone mineral density, proper screening and monitoring should be implemented. Bone mineral density is measured by dual energy X-ray absorptiometry and should be evaluated in those with persistent symptoms of the Triad.
References and for further readings related to this topic: