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What Is the Clinical Definition of Obesity?

Obesity is a growing problem in the western world. Studies show that due to unhealthy diet and lack of exercise, there is a sharp rise in clinical obesity—even among children.

Obesity is, technically speaking, a body mass index (BMI) of 30 or higher. BMI is arrived at by dividing a person’s weight in kilograms by his or her height in meters. This is more accurate than simply looking at someone’s weight—two people could be 130 pounds, but this could be a “healthy” weight for someone taller, and clinically obese for someone shorter.

When people are overweight they consume more calories than they burn. The body stores these unused calories in the form of fat. Some people tend to burn calories faster; they have a high “metabolic rate.” Some of this is determined by genetics, but anyone can increase metabolic rate by regular exercise.


Someone’s metabolic rate can go down because of a sedentary lifestyle, such as adults who hold desk jobs, or kids who prefer to watch TV all day. If they simultaneously take in a lot of calories—especially empty calories found in sugary or fatty foods—they gain weight and, over several years, become obese.

Obesity can lead to many health complications, such as increased risk for heart disease and stroke, infertility and depression. Left untreated, it can shorten lifespan by 9 years. Even slight obesity can affect quality of life. People report increased sweating (even when performing relatively simple activities) and general fatigue. Others suffer from irregular sleeping patterns, snoring, and arthritis.

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