Jonathan Purtell, MS, RDN, CDN, is a board-certified Registered Dietitian who provides in-patient services at Lenox Hill Hospital in New York, New York.
Obesity is a disease characterized by abnormal or excessive fat accumulation that can impair health. It’s a global health epidemic with more than 650 million people affected worldwide, according to the World Health Organization. Obesity is a contributing factor to many diseases, including:
The medical definition of obesity is based on body mass index (BMI)—your weight divided by height squared. People with a BMI of 30 or above are considered obese. Your doctor will also consider your BMI in the context of an overall health assessment.
BMI is a flawed measure that does not take into account factors such as body composition, ethnicity, sex, race, and age. Even though it is a biased measure, BMI is still widely used in the medical community because it’s an inexpensive and quick way to analyze a person’s potential health status and outcomes.
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.
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.
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.
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Rosen H. Is Obesity A Disease or A Behavior Abnormality? Did the AMA Get It Right? Mo Med. 2014;111(2):104-108.
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