Obesity means that a person is very fat. This is also called overweight. Another term is obesity, which comes from the Latin word "adeps" meaning "fat."
Obesity can happen when a person has a poor diet. Or it can be inherited. Many people who are obese also have health problems. For example, they get diabetes, heart disease, or high blood pressure. You can calculate obesity with a formula. This is called body mass index. If you have a body mass index above 30, you are extremely overweight.