Obesity rates in Canada increased after start of COVID-19 pandemic

A new study published in theCanadian Medical Association Journal found obesity rates based on body mass index (BMI) increased faster in the four years after the start of the pandemic than in the previous 11 years, especially in younger adults.

“Compared with the average increase during the 11 years before the pandemic, the prevalence of obesity [as measured by BMI] increased at a greater rate during the four years after the onset of the COVID-19 pandemic (2020–2023), suggesting that the COVID-19 pandemic and associated public health restrictions may have adversely affected obesity prevalence in Canada,” writes Dr. Laura Anderson, associate professor, Department of Health Research Methods, Evidence and Impact and co-director of the Center for Health Economics and Policy Analysis (CHEPA), McMaster University, Hamilton, Ontario, with co-authors.

Obesity is a risk factor for a range of diseases and can negatively affect a person’s health and well-being as well as increase the burden on the health care system. Rates in Canada were increasing before the pandemic, with higher rates of more severe obesity.

The large study, which included data on 746,250 adults aged 18 and older, looked at trends in BMI over 15 years, from January 2009 to March 2020 and from April 2020 to December 2023. Researchers found that BMI-defined obesity rates increased from 25% in 2009 to 33% in 2022, an absolute increase of about 8%.

After the pandemic started, obesity increased by just over 1 percentage point a year, about twice the pre-pandemic rate of increase. As well, obesity rates in males and females narrowed, with a 9% increase in obesity in females compared with a 7% increase in males. Obesity rates were highest in people who were white or Black.

“We observed important subgroup differences, with several groups that had a lower historical prevalence of obesity showing a substantial increase during the pandemic, including females and young adults. This raises concerns about potential adverse long-term consequences,” write the authors.

The authors observed a small increase in underweight adults during the study period and note that being underweight can have negative health effects. They caution that efforts to address rising rates of obesity should consider the unintended effects of weight control messaging on people with eating disorders.

Investment in research and approaches to obesity prevention and treatment are needed and should be a priority for funders and policy-makers.