Obesity, broadly defined as “a condition characterized by the excessive accumulation and storage of fat in the body,” has long been recognized as increasing the risk of human disease and death. Hippocrates, often called the “father of medicine,” noted in the fifth century B.C. that “sudden death is more common in those who are naturally fat than in the lean.”

Today, obesity is widely recognized to increase the risk of cancer, heart disease, stroke, high blood pressure and type 2 diabetes and was recently linked to an increased risk of death following a COVID-19 infection. According to the Centers for Disease Control and Prevention, over 40% of the U.S. population is obese.

The first question is: If obesity is such a large health problem, what do we know about how it is caused and how it can be treated? 

For centuries, people have assumed that obesity is due to behavior such as eating too much or exercising too little. Even Hippocrates attributed obesity to a sedentary lifestyle. In a 2018 survey, 80% of physicians and 68% of nurses said that lifestyle choices were the primary cause of obesity, and diet and exercise were the most recommended interventions.

In October 2022, the world’s leading obesity researchers met in London to discuss the causes of obesity. At the end of the meeting one of the organizers said, “There’s no consensus whatsoever about what the cause of it‌ is.” However, the researchers did agree that obesity is not a personal failing and is not due to a lack of willpower. In a recent report the American Academy of Pediatrics also concluded that obesity is not simply the result of personal choices but was a complex disease.

The second big question is: If obesity is not simply due to eating too much or exercising too little, then what is the cause? 

Although eating patterns and physical activity do play a role in obesity, scientists believe that interactions between genetics and the environment are also important. People’s home, work and play environments also have a major role. Our personal environment can affect the availability of healthy food, access to health care, the presence of pollutants and access to safe living.

One surprising observation is that the risk for obesity increases in people who skip meals and report being hungry due to food insecurity. Studies in animals have also shown that an erratic food supply leads to increased weight gain, possibly because of a physiological stress response that improves energy efficiency. 

As obesity is increasingly recognized as a chronic disease, experts recommend treating it as seriously as heart disease, high blood pressure or other chronic illnesses. Unfortunately, this is often not the case, and until the idea of treating obesity as a serious disease is more widely accepted, effective treatment and management strategies cannot take place.