The Major Causes of Obesity, According to Science

According to the Centers for Disease Control and Prevention, over 42 percent of American adults are considered obese. "Obesity is a serious chronic disease, and the prevalence of obesity continues to increase in the United States," they explain. In fact, they even use the word "epidemic" to describe the condition, which after smoking is the most preventable cause of death in the country. What exactly is it and what is its number one cause? Read on for everything you need to know about obesity.

Artur Viana, MD, Clinical Director Yale Medicine Metabolic Health & Weight Loss Program, points to the official definition of obesity: A chronic, relapsing, multifactorial, neurobehavioral disease, wherein an increase in body fat promotes adipose tissue dysfunction and abnormal fat mass physical forces, resulting in adverse metabolic, biomechanical, and psychosocial health consequences.

"To simplify, it is a disease that lasts for many years (chronic), which may improve then worsen (relapsing), has many different causes that can be present at the same time," Dr. Viana explains. "In obesity there is an increase in fat mass and the fat tissue (which is a tissue that is involved in many important regulatory steps in metabolism) is not working as it should."

While some people think about obesity in terms of looks, the damage it wreaks inside the body is what is the most concerning. "Obesity is serious because it is associated with poorer mental health outcomes and reduced quality of life," explains the CDC. 

Dr. Viana specifies that health complications can include organ system damage leading to different issues such as diabetes, joint disease, gastroesophageal reflux, among others.

Dr. Viana reveals that there isn't a perfect way to diagnose obesity but the most common way to do it is by calculating a BMI (body mass index). "This is a number that is obtained by dividing someone's weight in kilos by the square of their height in meters," he explains. 

A BMI of 30 or more is considered in the obese range. "However, this must be taken into consideration for each individual, since BMI is not a good reflection of health and does not consider body composition," he adds. For example, an athlete may have a BMI over 30 and not have obesity, for example, or someone may have a BMI of 31 and not really have a health-related issue.

There are many factors that contribute to obesity. "Obesity is multifactorial, meaning many factors are involved and go from genetics, lifestyle, mental health issues (such as trauma) to medication side effects," says Dr. Viana. 

"Behaviors can include physical activity, inactivity, dietary patterns, medication use, and other exposures," adds the CDC. "Additional contributing factors include the food and physical activity environment, education and skills, and food marketing and promotion."

According to Dr. Viana, there isn't one #1 cause. "Obesity medicine specialists wish there was a number one cause, as this would make treatment a lot easier," he reveals. But the NIH is a little more specific, saying the #1 cause is "by eating too much and moving too little…. If you consume high amounts of energy, particularly fat and sugars, but do not burn off the energy through exercise and physical activity, much of the surplus energy will be stored by the body as fat."

Luckily, obesity is preventable. "The best way to prevent it is to maintain a healthy lifestyle with exercise (the recommendation is at least 30 minutes of moderate-intensity exercise, 5 times a week) and healthy diet, which is one that contains minimal processed food and focuses on whole foods such as lean protein, whole grains, vegetables, and fruits," suggests Dr. Viana. 

If you are obese, you should take action immediately. "If you struggle with weight gain and you feel unhealthy or believe it is affecting you in some way, talk to your primary care provider and they will be able to counsel you and if needed provide a referral to an obesity medicine specialist," suggests Dr. Viana.