From 1999-2000, an estimated 30.5% of Americans were obese. By 2017-2018, that number had risen to 42.5%, costing those who are obese roughly $1,429 more in healthcare expenses than people of a normal weight, according to the Centers for Disease Control and Prevention.
Since obesity is on the rise and related to so many negative health effects, it’s important that doctors can easily define obesity in order to help patients take control of their health.
“We want to come up with a universal way of defining obesity, because different cultures define it differently,” says Mir Ali, MD, bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center. “So the thing we have that isn’t the most accurate, but at least it’s a common reference point, is the body mass index (BMI).”
BMI is the most standard way for doctors and patients to determine if someone is overweight or obese. It’s calculated with a formula that takes into account your height and weight and there are many online BMI calculators you can use to easily calculate your own BMI. Here’s what you need to know about BMI, it’s role in determining obesity, and why it’s not always the best tool.
The three tiers of obesity
According to the CDC, a BMI of 25.0 to 29.9 is considered overweight, and a BMI of 30 or above is obese. Additionally, there are three subcategories, or classes, of obesity based on BMI. According to the CDC, Class 1 is a BMI of 30 to 35, Class 2 is a BMI of 35 to 40, and Class 3 is a BMI of 40 or higher.
“Someone with a BMI of 40 has a two to three times greater risk of developing obesity related diseases [than someone with a healthy BMI],” says Ali, adding that these classes are also important to help doctors decide what kind of treatment is necessary.
If you have a BMI greater than 40, then you could qualify for bariatric surgery. Whereas, if you have a BMI between 30 and 40 and have struggled to lose weight through diet and exercise, your doctor may prescribe a diet pill to aid weight loss.
However, BMI is not a be all end all to measure obesity. For example, a high BMI doesn’t always mean obesity. “The BMI calculation doesn’t take into account anybody’s body composition, and that can affect how healthy they are. A 300-pound bodybuilder with 5% body fat [may be] healthy, but if you plug him into the BMI formula, he [will] come out obese,” says Ali.
Other ways to measure obesity
Aside from BMI, there are a few other more accurate ways to measure obesity and the risk of obesity-related disease:
- Waist circumference: Measuring around the waist at the level of your navel with a tape measure will give you your waist circumference. According to Harvard Medical School, the risk of obesity-related disease is high for a man with a waist circumference of 40 inches or more and a woman with a waist circumference over 35 inches.
- Waist-to-hip ratio: For this method, take your waist circumference and divide it by the circumference of your hips at their widest point. The number you get will be your wait-to-hip ratio. You’re at high risk for obesity-related health problems if your ratio is above 0.95 in a man, or above 0.85 in a woman.
- Skinfold thickness: This method involves using a skinfold caliper, which is like a hand held clamp, to determine the thickness of the skin folds in a certain area, thereby determining the percentage of body fat. Then, you can plug the measurements from the caliper into an online calculator to get your body fat percentage. In general, body fat over 25% in a man is considered obese, and body fat over 32% in a woman is considered obese.
- Bioelectrical impedance: Bioelectrical impedance analysis (BIA) is a method that can analyze body fat percentage by sending an electrical current through the body. This is actually an available feature on some home bathroom scales. Since body fat isn’t a great conductor of electricity, the higher resistance score you get, the more body fat you’re likely to have.
- Dual-energy X-ray absorptiometry (DXA) scan: According to Ali, a DXA scan is one of the most accurate ways to measure body fat and obesity because it’s very precise. “A DEXA scan uses low dose X-ray at different energy levels to assess body composition. Each component of the body (muscle, fat, bone), absorbs the energy directly and that difference can be used to calculate not only bone, but fat composition as well,” says Ali.
While this one is very accurate, Ali says it isn’t readily available to the general public, and it’s expensive. The test usually isn’t offered at typical X-Ray/imaging centers, and most people don’t actually require this precise level of accuracy to make treatment choices.
Obesity and fitness
Being obese does not automatically mean you are unhealthy. The importance of exercise in obese people has been extensively researched.
For example, a study published in BMC Obesity in 2018, showed that somebody who is severely obese but very active can be as healthy as someone who is moderately obese and does not exercise very much. Additionally, a 2017 study published in the European Journal of Preventive Cardiology concluded that obese people who regularly worked out had less risk of cardiovascular disease than obese people who were inactive.
“The less active you are as an obese person, the more likely you’ll be to develop health issues,” says Ali. “Activity helps keep your cardiovascular health strong, helps to reduce your risk of degenerative changes in the joints, and other health issues, so activity is important.”
Fitness is so important for health because it helps prevent the build-up of visceral fat, which lies beneath the abdominal muscles surrounding vital organs like the liver, intestines, and stomach. Visceral fat is one of the biggest risk factors in obese people for developing health problems.
If you are obese or think you may be obese, it’s important to keep active and eat healthily to avoid the complications that can be caused by obesity. Speak to your doctor or an obesity specialist to get on the right track.