The findings of this study are described in the September 2, 2004 issue of The New England Journal. Christos Mantzoros, M.D., Director of the Human Nutrition Research Unit and Clinical Research Overseer of the Department of Endocrinology at BIDMC and Associate Professor of Medicine at Harvard Medical School explained that this study has particular relevance for three groups of women. These women have one thing in common – low levels of body fat.
According to Dr. Mantzoros, “The largest group is made up of extremely thin women who are dealing with problems of infertility; the second group consists of competitive athletes and dancers whose thin frames put them at risk for developing osteoporosis and suffering bone fractures; and the smallest – but most extreme – group is women who are battling eating disorders, such as anorexia nervosa.”
Leptin is often recognized as an appetite and weight regulation hormone. But did you know that the hormone leptin also serves an indicator that tells the brain and other organs when extremely low energy is available?
Mantzoros goes on, “We know that leptin is produced by the body’s fat tissue and is secreted into the bloodstream in proportion to the amount of energy stored in fat. From there, it travels to the brain where it communicates exactly how much energy is available.” Because of this process, leptin regulates a number of important physiological functions that depend on adequate energy balance. These physiological functions include reproduction, metabolism, and bone function.
As a result, when women have severely low levels of body fat, which may occur after excessive dieting or exercise or in women with eating disorders, the body enters a state of “negative energy balance” that adversely affects reproductive function and metabolism according to Dr. Mantzoros.
“Women stop menstruating and develop hypothalamic amenorrhea, their ovaries cease to function, and their levels of estrogen and other reproductive hormones drop dramatically,” explained Mantzoros. Amenorrhea (absence of menstruation) is also associated with a number of other conditions including abnormal thyroid hormone levels, abnormal growth factor levels, and loss of bone mass. Loss of bone mass can lead to osteoporosis and broken bones.
