Canada Is Redefining Obesity: Where Does the U.S. Stand?

A team of Canadian doctors released new guidelines last week to encourage physicians to revisit the way they diagnose and treat patients with obesity. Now, American doctors are considering the benefits and challenges of changing their approach.

The guidelines, which were published in the Canadian Medical Association Journal, say that obesity should be defined by a patient’s overall health, not just their weight. They also urge the medical community to classify obesity as a chronic illness that needs long-term care and treatment.

The guidelines specifically recommend that doctors shift “the focus of obesity management toward improving patient-centered health outcomes, rather than weight loss alone.”

It’s a significant departure from the current way obesity is diagnosed in Canada—and the U.S.

“Canada is, in a way, doing better with this,” Fatima Cody Stanford, MD, MPH, MPA, an obesity medicine physician and clinical researcher at Massachusetts General Hospital, tells Verywell. “Body mass index isn’t the only measure we should be using."

How Obesity Is Currently Diagnosed

According to the World Health Organization, obesity can be measured by dividing a person’s weight (in kilograms) divided by the square of their height (in meters). This number give you body mass index, or BMI. A BMI of 30 or higher is considered obese, and a BMI of 25 to 29 is considered overweight.

In Canada, 26.8% of adults are considered obese. In the United States, this figure is 42%.

In the U.S., obesity is divided into three categories by the Centers for Disease Control and Prevention (CDC):

• Class 1: BMI of 30 to less than 35
• Class 2: BMI of 35 to less than 40
• Class 3: BMI of 40 or higher. Class 3 obesity is sometimes categorized as “extreme” or “severe” obesity.

The New Guidelines Recommend Take a Broader Perspective

The new guidelines encourage doctors to view obesity in the greater landscape of a person’s health. The guidelines lay out a very specific five-step plan for doctors regarding obesity management:

1.  Doctors should ask for permission to discuss a patient’s weight. Asking permission shows empathy and builds patient-provider trust, the guidelines say.

2.  Doctors will assess a patient’s story. This involves talking to the patient about their goals, their obesity classification (factoring in BMI and waist circumference), and their disease severity.

3.  Doctors will give medical advice. This can include medical nutrition therapy, recommendations on exercise, psychological therapy, medications, and bariatric surgery.

4.  Doctors and patients will agree on goals. Together, they’ll collaborate on a personalized plan of action.

5.  Doctors will help patients reach their goals. That includes doctors being supportive and helping patients identify barriers to their goals.

American Doctors Applaud the Move

“These guidelines are trying to be more mindful of actual health," Stanford says. “The problem is with BMI is it doesn’t give us a lot of information–it only tells us someone’s height and weight.”

BMI leaves out whether someone has adipose tissue (body fat around their organs), is struggling with excess water weight, and their overall body composition, Stanford says. BMI also doesn't take into account factors such as ethnicity, sex, race, and age. 

BMI also puts a large emphasis on a number on the scale, which Stanford says can be "defeating" for patients. “I never give patients a target weight; one person’s ideal may be different from mine or yours," she says. "If a patient starts at a high weight—say, 500 pounds—and they get to 300 pounds, do we say that they failed? If I gave them a target weight of 200 pounds, and they ‘only’ got to 300, they would think they failed.”

Still, BMI has a role in obesity medicine.

“Even though it’s not the ideal calculation to determine someone’s obesity, we haven’t come up with an alternative yet that you can use instead of the BMI,” Mir Ali, MD, medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, California, tells Verywell.

Ali says the Canadian approach to obesity is “practical, but time intensive."

“It can be difficult to spend that much time with a patient to come up with a treatment plan,” he says. However, a primary care physician or initial care provider should “start the patient on the process to maintain a healthy weight and take an overall look at the patient’s health.”