What percentage of body fat is considered too low?
A certain amount of fat is necessary for normal physiologic functioning. For men, this level of essential fat appears to be 2-5% of total body weight, whereas women have approximately 5-10% essential fat. For women, minimal fat levels have a much greater individual variation. There may be a critical level of body fat necessary for the normal production and effectiveness of estrogen. There appears to be an increased incidence of amenorrhea (absence of menstruation following menarche for a period of six months or three regular cycles) among women athletes. However, many women under 18% body fat have normal menstrual cycles, and others may become amenorrheic at “normal” percents of body fat. There appears to be a significant correlation between a deficient estrogen level and osteoporosis. This may put the amenorrheic athlete with low estrogen levels potentially at risk for decreased bone density and a greater likelihood of stress fractures doing physical training or osteoporosis fractures
