The idea that a leaner body makes for a faster stride is common among distance runners. But it’s inaccurate and sets a dangerous ideal. Runners who are excessively lean are prone to injuries, infectious diseases, mental health problems and loss in bone density, said Michael Fredericson, MD, a professor of orthopaedic surgery who has served for decades as the Stanford University track team head physician. Female runners are more likely to suffer these effects, he noted.
During his career as the head team physician, Fredericson has seen so many athletes with problems related to low body weight — including bone stress injuries, menstrual irregularity and osteoporosis, or loss of bone density — he decided to study ways to prevent it.