The term obese describes a person who's very overweight, with a lot of body fat.
It's a common problem in the UK that's estimated to affect around 1 in every 4 adults and around 1 in every 5 children aged 10 to 11.
How to tell if you're obese
The most widely used method to check if you're a healthy weight is body mass index (BMI).
BMI is a measure of whether you're a healthy weight for your height. You can use the NHS BMI healthy weight calculator to work out your score.
For most adults, a BMI of:
18.5 to 24.9 means you're a healthy weight
25 to 29.9 means you're overweight
30 to 39.9 means you're obese
40 or above means you're severely obese
BMI is not used to diagnose obesity because people who are very muscular can have a high BMI without much fat.
But for most people, BMI is a useful indication of whether they're a healthy weight.
A better measure of excess fat is waist size, which can be used as an additional measure in people who are overweight (with a BMI of 25 to 29.9) or moderately obese (with a BMI of 30 to 34.9).
Generally, men with a waist size of 94cm or more and women with a waist size of 80cm or more are more likely to develop obesity-related health problems.