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.
Causes of obesity
Obesity is generally caused by consuming more calories, particularly those in fatty and sugary foods, than you burn off through physical activity. The excess energy is stored by the body as fat.
Obesity is an increasingly common problem because for many people modern living involves eating excessive amounts of cheap high-calorie food and spending a lot of time sitting down at desks, on sofas or in cars.
There are also some underlying health conditions that can occasionally contribute to weight gain, such as an underactive thyroid gland (hypothyroidism), although these types of conditions do not usually cause weight problems if they're effectively controlled with medicines.
The best way to treat obesity is to eat a healthy reduced-calorie diet and exercise regularly.
To do this, you should:
- eat a balanced calorie-controlled diet as recommended by a GP or weight loss management health professional (such as a dietitian)
- join a local weight loss group
- take up activities such as fast walking, jogging, swimming or tennis for 150 to 300 minutes (2.5 to 5 hours) a week
- eat slowly and avoid situations where you know you could be tempted to overeat
You may also benefit from receiving psychological support from a trained healthcare professional to help change the way you think about food and eating.
If lifestyle changes alone do not help you lose weight, a medicine called orlistat may be recommended.
If taken correctly, this medicine works by reducing the amount of fat you absorb during digestion. Your GP will know whether orlistat is suitable for you.
In some cases, weight loss surgery may be recommended.
Adults are generally considered obese if they have a body mass index of 30 or above.
The main treatment for obesity is a reduced-calorie diet and an exercise plan. Less common treatments include weight loss medicines and surgery.
Obesity is usually caused by eating and drinking too much and moving too little.
HealthUnlocked contains information from NHS Digital, licensed under the current version of the Open Government Licence