Final answer:
An adult with a BMI of 40 or greater is classified as morbidly obese, although a BMI of 35 or above can also qualify if there are additional health concerns. The BMI scale, while common, has limitations, particularly when it doesn't distinguish between muscle and fat mass.
Step-by-step explanation:
A person is classified as morbidly obese when their body mass index (BMI) reaches a certain threshold. An adult with a BMI of 40 or greater is considered to be morbidly obese. However, a person with a BMI ≥ 35 kg/m² can also be classified as morbidly obese if they have obesity-related health problems. In contrast, a BMI between 25 and 29.9 is considered overweight, while a BMI of 30 or higher is generally classified as obese.
It is important to understand that while the BMI is a useful tool for studying populations, many experts question its value for assessing individual health since it does not differentiate between body fat and muscle mass. An athlete, for instance, might have a high BMI due to muscle mass but is not necessarily carrying excess body fat. Thus, the context of the individual's overall health and body composition should be taken into account when evaluating BMI.