Clinically, overweight is defined as having a body mass index (BMI) between 25.0 and 29.9. Body mass index is a value calculated directly from a person's height and weight.
People classified as obese have BMIs ranging from 30.0 to 39.9. Those with BMIs of 40 and above are classified as extremely obese.
Many use BMI as a comprehensive indicator of a person's overall health. Because of this, those who are "overweight" are often considered unhealthy or "at risk," regardless of other health indicators. BMI, in particular, does not take into account how weight is distributed (in muscle, bone, fat, water, etc.). In short, though the state of being overweight is correlated with having a higher percentage of body fat than being of normal weight, an individual can be clinically overweight and not have an overabundance of body fat.
Because children and teens are still growing, their BMIs are used differently. Children and teens in the 95th percentile of BMI for their ages are considered overweight.

