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URL of this page: https://medlineplus.gov/lab-tests/obesity-screening/

Obesity Screening

What is obesity screening?

Obesity screenings check for obesity and overweight in adults and children, starting as early as age 2. In general, having obesity and being overweight both mean that your weight is higher than what is considered healthy for your height:

  • Obesity means that you have too much body fat.
  • Overweight usually means that you have too much body fat. But the extra weight may come from muscle, bone, and/or holding too much water in your body.

Extra fat from obesity and overweight increases your risk of developing serious, long-lasting health problems, such as:

The more fat you have, the higher your risk of developing these problems. Children who have obesity may develop many of the same health problems as adults with obesity. They are also more likely to have obesity in adulthood and develop serious health problems later in life.

Obesity screening helps find out if too much body fat could be a health concern for you. Measuring body fat is difficult and expensive. So, obesity screening estimates how much body fat you have. The estimate is made with a calculation called a BMI (body mass index).

How is a BMI calculated?

BMI for adults ages 20 and older is calculated from height and weight information. The result is a number called a BMI score. Higher BMI scores are linked to larger amounts of body fat and a higher risk for certain health problems. For most adults:

  • A healthy weight is a BMI between 18.5 and 24.9
  • Overweight is a BMI between 25 and 29.9
  • Obesity is a BMI of 30 and above

BMI for children over age 2 and teens is also based on weight and height. But age and sex are part of figuring out if a child or teen has too much body fat. That's because the normal amount of body fat is different at each stage of growth. And the normal amount of fat is different for boys and girls.

To adjust for these differences, your child's BMI is compared to standard growth charts for children of their age and sex. The result is called a BMI percentile. For example, if your child's BMI is in the 25th percentile, it means that 25% percent of children the same age and sex have a lower BMI, and 75% percent have a higher BMI.

Because height and weight changes with growth, your child's BMI will be tracked over time to understand if obesity or overweight may be a health problem. For most children and teens:

  • A healthy weight is a BMI between the 5th and 85th percentile.
  • Overweight is a BMI between the 85th and 94th percentile.
  • Obesity is a BMI in the 95th percentile or higher.

A BMI is a fairly accurate way to screen most people for too much body fat, but it's not perfect. Your BMI can't tell if your weight is from extra fat or muscle. This means a very muscular person could have a BMI in the overweight range even though they don't have too much body fat.

Also, some people who have a healthy BMI may still have high amounts of body fat. This may be more common in groups that tend to have lower BMI scores, such as Asians and older adults who have lost muscle. Talk with your health care provider if you have questions about how accurate a BMI is for your body type.

What is an obesity screening used for?

An obesity screening with a BMI is used to find out if an adult or a child has an unhealthy body weight for their height. This helps a provider understand a person's risk for diseases that are linked to extra body fat. But obesity screening doesn't show the amount of fat a person has, and it can't diagnose any health conditions, so other tests may be needed.

A BMI may also be used to find out if weight-loss efforts are working.

Why do I need obesity screening?

Most adults and children ages 2 and older should be screened with a BMI at least once a year.

Yearly obesity screening tracks your BMI over time. If it gets higher, it usually means you're gaining extra fat. Even if your higher BMI stays in the healthy range, weight gain from fat can still increase your risk for weight-related diseases. Obesity screening can help catch weight gain early so you can take steps to control your weight before it harms your health.

If you already have obesity or are overweight, screening helps your provider monitor your risk for health problems related to body fat. Information about your risk level helps you and your provider consider the pros and cons of different weight-loss treatments.

What happens during an obesity screening?

An obesity screening is usually part of a routine checkup that includes a physical exam. Your provider will measure your height and weight. That information is usually entered into an online BMI calculator. If you know your height and weight, you can find your BMI online:

Your provider may also use other tests to estimate how much body fat you have. These include:

  • A waist measurement. Adults who have too much fat around their abdomen (belly) have an increased risk of developing conditions related to obesity. Even if you have a healthy BMI, your risk may be high if your waist size is:
    • More than 40 inches for men
    • More than 35 inches for women who aren't pregnant
  • Skinfold measurements. A skinfold test measures the thickness of pinch of skin and fat at several places on your body. A special tool gently measures skinfolds on your belly, back, thigh, the back of your upper arm, and/or other places on your body. The results are used to estimate how much of your body is fat.

If your obesity screening shows that you may have too much body fat, your provider may ask questions to help find out why. This often includes discussing your:

  • Medical history and medicines you take. Some health conditions cause people to gain weight, such as metabolic syndrome, hypothyroidism, and polycystic ovary syndrome (in females only). Your provider may order blood tests to confirm or rule out these and other conditions.

    Many medicines can cause weight gain, too. Examples include:

  • Eating habits. Obesity and overweight develop over time when you take in more calories than you use. So, your provider will want to know how much you eat and drink. What you eat and drink matters, too. Too much saturated fat and sugar can cause weight gain.
  • Physical activity. A lack of physical activity is linked with weight gain. Your provider will want to know how much exercise you get and how much time you spend sitting.
  • Sleep habits. Not getting enough sleep or poor-quality sleep can make you more likely to overeat. That's because sleep affects hormones that control hunger.
  • Stress levels. Stress can affect your brain and trigger changes in your hormones that make you eat more and store more fat.
  • Family history. You're more likely to become obese if close family members have obesity. You may have inherited genes that affect weight. The eating and exercise habits of the people around you can affect your habits and weight, too.

Will I need to do anything to prepare for an obesity screening?

You don't need to prepare for an obesity screening. If you're also having certain blood tests to learn more about your health, you may need to fast (not eat or drink) for a period of time. Your provider will let you know how to prepare.

Are there any risks to the screening?

There is no risk to having a BMI or a measurement of your waist or skinfolds.

What do the results mean?

If an obesity screening shows that you have obesity or are overweight, your provider will work with you to develop a treatment plan. The goal of the plan is to reduce your risk of health problems linked to extra body fat.

Your plan will depend on how much weight you need to lose and the cause of your weight gain. Most plans are likely to include lifestyle changes, such as:

Depending on your BMI and health, you provider may also suggest:

  • Support from a dietary or nutritional counselor
  • A behavioral weight-loss treatment program
  • Prescription weight-loss medicines combined with lifestyle changes
  • Weight loss surgery or devices, such as balloons, that are put in the stomach to help you lose weight

If you have questions about obesity screening or treatments to lower your BMI, talk with your provider.

Learn more about laboratory tests, reference ranges, and understanding results.

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The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.