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If you think you are obese and you want to do something about it, your doctor should be able to help.

Your doctor will probably work out your body mass index (BMI for short) and your waist and hip measurements.^{1 2} These figures can help your doctor decide whether your weight is likely to seriously affect your health.¹ Your doctor will also ask about your general health and any other conditions you have.

To read more about what to expect, see Questions your doctor may ask.

There are several other tests that can measure how much fat you're carrying. But these tests aren't usually available in family clinics.

Most doctors will work out your BMI. It tells the doctor whether your weight is healthy. It's worked out according to both your height and weight.

Your doctor will weigh and measure you. These numbers go into a math formula that gives a single number. This is your BMI.^{1 3} You can work out your own BMI. This table shows what different BMI scores mean.

Working out someone's BMI isn't a perfect way of telling if they are overweight. For example, an athlete who's very muscular may have a BMI that suggests they're overweight, even though they're healthy. That's because muscle is heavier than fat. However, for most people, working out their BMI is a quick and simple way of finding whether their weight is healthy. If your doctor thinks your BMI might be misleading, he or she can take other measurements to work out if you're overweight.

It's not only how much fat you have that matters. Your risk of getting conditions such as heart disease and diabetes also depends on where you carry this fat.

People who are "apple-shaped," with a lot of fat around their waist and chest, are more likely to get these conditions then people who carry weight on their hips and buttocks ('pear-shaped').

The table below shows how your waist measurement can affect your chance of getting health problems.^{1 3 4} The numbers we give are for a measurement taken just above the top of your hips, roughly at the level of your belly button. It might not be the same as your clothes size.

Your doctor may want to work out your waist-hip ratio. It's your waist measurement divided by your hip measurement.

For example, if your waist is 34 inches and your hips are 40 inches, your waist-hip ratio is 0.85.

If you're a man, you're at high risk of health problems if:⁵

• Your waist-hip ratio is more than 1.0

If you're a woman, you're at high risk of health problems if:⁵

• You're "apple-shaped," and
• Your waist-hip ratio is more than 0.9.

Your doctor might check whether you have a medical condition that is causing you to put on weight. For example, you may have a problem with your thyroid gland. This gland makes hormones that change the way your body uses energy.

Women may have a condition called polycystic ovary syndrome. This can cause women to gain weight.

See Conditions that can cause obesity.

Your doctor may also run tests to see if you have conditions that can be made worse by your weight. For example, you may need tests for high blood pressure, diabetes or high cholesterol.

If you have one of these extra conditions, losing weight may be even more important for your health.^{1 6 7}

You and your doctor may decide that your weight is a problem for your health. If you decide you would like to lose weight, you and your doctor will need to draw up a weight loss program. This could include:^{1 6 7}

• Changing your diet
• Increasing your physical activity
• Having therapy to support these changes
• Considering treatments such as drugs or surgery.

To read more about losing weight, see What treatments work for obesity?

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.