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The prevalence of BMI-defined obesity in Canada increased at a greater rate during the first 4 years after the onset of the COVID-19 pandemic than during the 11 years before the pandemic, new research suggested.

Young women, who had a lower prevalence of obesity before the pandemic, showed a substantial increase in obesity prevalence and severity during the pandemic.

“We know the COVID-19 pandemic resulted in all sorts of changes in health behaviors,” study author Laura N. Anderson, PhD, assistant professor of health research methods, evidence, and impact at McMaster University in Hamilton, Ontario, told Medscape Medical News.

The findings were published on July 14 in the Canadian Medical Association Journal. 

Changing Risk Factors

“It is expected that many of the risk factors for obesity, including changes in physical activity, increased sedentary time, and changes in dietary patterns and access to healthy foods for some individuals, have changed,” Anderson said.

“Other risk factors for obesity that also changed during the pandemic were mental health and increased risk for anxiety and depression. Even the stress that we were all experiencing at that time could also be a risk factor for obesity,” she added.

The investigators examined data from the Canadian Community Health Survey to identify trends in the prevalence of obesity from January 2009 to March 2020 and from April 2020 to December 2023. They found that obesity prevalence increased from 24.95% in 2009 to 32.69% in 2023, indicating an absolute increase of 7.74%.

After the pandemic started, obesity prevalence increased by just over 1% per year, which was about double the pre-pandemic rate of increase. The severity of obesity also increased. In 2009, the rate of Class I obesity was 17.38%; in 2023, it was 20.11%. During the same period, the rate of Class II obesity increased from 5.21% to 7.65%, and the rate of Class III obesity increased from 2.37% to 4.93%.

During the COVID-19 pandemic and over the entire study period, the greatest increase in obesity prevalence was observed among younger adults. Young women experienced the greatest increases compared with other groups. The increase was nearly 9% overall and 13.11%-21.71% for women aged 18-29 years.

The prevalence of obesity was highest among patients who self-identified as White or Black compared with those who identified as Asian (P < .001). In addition, the prevalence of obesity tended to be lowest among people in the highest income quintile.

“One of the limitations of our study is that we relied on BMI as a measure of obesity, and BMI is not necessarily a perfect measure. It doesn’t directly measure body fat, and we know that it doesn’t measure health conditions. So, if you are a clinician evaluating individuals who may have obesity, it’s important to investigate beyond just whether they have a high BMI,” Anderson said.

Obesity is a complex condition with multiple causes, she added. “There really is not a one-size-fits-all approach for prevention and treatment. We need to invest in public health to support healthy behaviors. We need the government to invest in health policies that promote healthy communities and the availability of healthy foods. And we need improved health systems for early treatment, in Canada in particular, as people sometimes have a hard time finding a primary care provider.”

The Perfect Storm

Commenting on the findings for Medscape Medical News, Lesley Lutes, PhD, director of the Center for Obesity and Well-Being Research Excellence at the University of British Columbia in Kelowna, British Columbia, said, “The findings are expected, given research that showed how the COVID-19 pandemic impacted individual caloric intake, physical activity, and mental health.” Lutes did not participate in the research.

“The COVID-19 pandemic, unfortunately, was a perfect storm to impact all these things at the same time, which clearly impacted people’s weight and level of risk,” she added.

An unfortunate omission of the study was the exclusion of patients living in territories and on reservations, said Lutes. “It really did not allow us to understand how indigenous individuals living on reservations or in the territories have been specifically or differentially impacted, but my guess is that this group would have fared even worse.”

Lutes agreed that Canada must invest more to improve preventive mental and behavioral health care services. “Canada is decades behind in investing in preventive mental and behavioral healthcare. This [investment] has been repeatedly shown to not just improve mental and physical health, but also reduce healthcare utilization, hospitalization, and chronic diseases such as diabetes, cardiovascular disease, and cancer. Such investment also improves the gross domestic product. Countries such as Norway, Sweden, Finland, and Denmark have the highest levels of health and the highest levels of well-being and happiness.”

In 2020, the Canadian Medical Association published a clinical practice guideline for the treatment of adults with obesity. “The statement advised that people should stop being given exercise and nutrition recommendations and instead be given evidence-based cognitive behavioral therapy that helps address the root drivers for the behaviors impacting weight gain,” Lutes said.

“But we have not yet given our physicians the wherewithal to provide mental and behavioral health services as part of healthcare, and they can’t do this unless they have access to these treatments. So, we let people who are overweight and obese languish for years and don’t provide them weight management treatment, behavioral treatment, or cognitive behavioral therapy for depression. Instead, we provide millions of dollars in treatment for when they get cancer, diabetes, or cardiovascular disease. Diabetes is the fastest-growing financial driver in the healthcare system. The answer is to go upstream and provide preventive mental and behavioral health care,” she said.

The study was supported by the Canadian Institutes of Health Research. Anderson and Lutes reported having no relevant financial relationships.