Obesity is an "abnormal or excessive accumulation of fat that presents a risk to health." There are several ways to measure a person's body fat percentage, including waist circumference, waist-to-hip ratio, skinfold measurements, and body mass index (BMI). Obesity increases the risk of serious health conditions like cardiovascular disease, type 2 diabetes, sleep disorders, and certain cancers. Common treatments for obesity include healthy eating and physical activity.
Someone with a body mass index (BMI) of 40 or greater, or who weighs 100 pounds or more above their body weight, is considered morbidly obese (also called severely obese or class 3 obese). Morbid obesity is associated with higher risks of disease, shorter life expectancy, and lower quality of life. BMI is a tool used to diagnose obesity, despite its flaws.
Being medically overweight is defined as having a body mass index (BMI) between 25 and 29.9. If you’re overweight, you may be at increased risk of certain health conditions, including high blood pressure, heart disease, and type 2 diabetes.
Physical activity can be exercise or “any bodily movement produced by skeletal muscles that require energy expenditure,” according to the World Health Organization (WHO). Regular physical activity may improve numerous aspects of your health, reduce your risk of certain diseases, help you feel more energetic, and control your weight.
Weight gain means getting heavier. While it can be a sign you’re taking in more calories than you’re expending, some weight gain is natural due to aging, pregnancy, hormonal shifts, fluid retention, and certain diseases. However, rapid weight gain without an obvious cause may be a symptom of serious illness. Be sure to contact your doctor if you suddenly gain weight and don’t know why.
Yes, the American Medical Association (AMA) defines obesity as a disease that stems from a complex mixture of factors including genetics, environment, and behavior. It’s considered an epidemic in the United States, with more than a third of the population estimated to be obese.
You’re generally considered obese if your body mass index (BMI) is 30 or higher. BMI is calculated by dividing your weight by your height squared. However, that number doesn’t take into consideration important factors such as muscle mass or frame size. Your doctor should consider the number in the context of your overall health when determining whether you’re obese.
Obesity is caused by an energy imbalance between calories consumed and calories expended, although some people are more predisposed to obesity than others.
Factors that contribute to obesity include:
Obesity is mostly preventable with a healthy lifestyle:
While this is especially important for those with a family history of obesity, medical conditions that contribute to weight gain, and other risk factors, everyone’s health can benefit from these strategies.
World Health Organization. WHO European Regional Obesity Report 2022.
Powell-Wiley TM, Poirier P, Burke LE, et al. Obesity and cardiovascular disease: A scientific statement from the American Heart Association. Circulation. 2021;143(21):e984-e1010. doi:10.1161/CIR.0000000000000973
National Institute of Diabetes and Digestive Kidney Diseases. Treatment for overweight & obesity.
University Health Care System. About Morbid Obesity - What is Obesity?
World Health Organization. Physical Activity.
Rosen H. Is Obesity A Disease or A Behavior Abnormality? Did the AMA Get It Right? Mo Med. 2014;111(2):104-108.