Different eating disorders affect the heart differently, said Mehler, who also is a professor of medicine at the University of Colorado School of Medicine. In people with anorexia, malnutrition and weight loss can cause the heart muscle to shrink and the heart rate to slow, a condition known as bradycardia in which the heart rate is less than 60 beats per minute at rest. Anorexia also can cause other abnormal heart rhythms.