What is obesity? Body mass index (BMI) is a calculation that takes a person’s weight and height into account to measure body size. In adults, obesity is defined as having a BMI of 30.0 or more , according to the Centers for Disease Control and Prevention (CDC). Obesity is associated with a higher risk for serious diseases, such as type 2 diabetes, heart disease, and cancer. Obesity is common. The CDC estimates that 42.4 percent of Americans 20 years old and older had obesity in 2017 to 2018. But BMI isn’t everything. It has some limitations as a metric. According to the CDC : “Factors such as age, sex, ethnicity, and muscle mass can influence the relationship between BMI and body fat. Also, BMI doesn’t distinguish between excess fat, muscle, or bone mass, nor does it provide any indication of the distribution of fat among individuals.” Despite these limitations, BMI continues to be widely used as a way to measure body size.

How is obesity classified? The following classes are used for adults who are at least 20 years old: BMI Class 18.5 or under underweight 18.5 to <25.0 “normal” weight 25.0 to <30.0 overweight 30.0 to <35.0 class 1 obesity 35.0 to <40.0 class 2 obesity 40.0 or over class 3 obesity (also known as morbid, extreme, or severe obesity)

What is childhood obesity? For a doctor to diagnose a child over 2 years old or a teen with obesity, their BMI has to be in the 95th percentile for people of their same age and biological sex: Percentile range of BMI Class >5% underweight 5% to <85% “normal” weight 85% to <95% overweight 95% or over obesity From 2015 to 2016, 18.5 percent (or about 13.7 million) American youth between 2 and 19 years old were considered to have clinical obesity.

How is obesity treated? If you have obesity and been unable to lose weight on your own, medical help is available. Start with your primary care physician, who may be able to refer you to a weight specialist in your area. Your doctor may also want to work with you as part of a team helping you lose weight. That team might include a dietitian, therapist, or other healthcare staff. Your doctor will work with you on making needed lifestyle changes. Sometimes, they may recommend medications or weight loss surgery as well. Learn more about treatment for obesity.

Which medications are prescribed for weight loss? Your doctor may also prescribe certain prescription weight loss medications in addition to eating and exercise plans. Medications are usually prescribed only if other methods of weight loss haven’t worked and if you have a BMI of 27.0 or more in addition to obesity-related health issues. Prescription weight loss medications either prevent the absorption of fat or suppress appetite. The following are approved for long-term use (at least 12 weeks) by the Food and Drug Administration (FDA): phentermine/topiramate (Qsymia)

naltrexone/bupropion (Contrave)

liraglutide (Saxenda)

orlistat (Alli, Xenical), the only one that’s FDA-approved for use in children 12 years old and older These drugs can have unpleasant side effects. For example, orlistat can lead to oily and frequent bowel movements, bowel urgency, and gas. Your doctor will monitor you closely while you’re taking these medications. WITHDRAWAL OF BELVIQ In February 2020, the FDA requested the weight loss drug lorcaserin (Belviq) be removed from the U.S. market. This is due to an increased number of cancer cases in people who took Belviq compared to placebo. If you’re taking Belviq, stop taking it and talk with your healthcare provider about alternative weight management strategies. Learn more about the withdrawal here and here.