Weight-loss drugs in Canada: What experts want you to know

Feet and lower legs of a person in jeans standing on a scale.

Obesity and diabetes researchers Zubin Punthakee and Katherine Morrison share information on how weight-loss medications work, and what we still need to learn. (Adobe Stock image

Diet and exercise have long been the go-to duo to help address obesity, a chronic condition that impacts 30 per cent of Canadians, but researchers say the arrival of specialized weight-loss medications could be a major catalyst for people who need an extra bit of help to be healthier.

Weight-loss drugs aren’t new to Canada. The first medication to receive approval for use was Xenical in 1999. More than 20 years later, it’s difficult to go a day without hearing about drugs like diabetes medication Ozempic, which skyrocketed in popularity in 2023 due to its main ingredient, Semaglutide, showing potential of helping people with weight loss.

Semaglutide is also the key ingredient in Wegovy, a weight-loss specific medication that entered the Canadian market in May 2024.

We spoke with Zubin Punthakee and Katherine Morrison, obesity and diabetes researchers with McMaster University, about weight-loss medications, how they work and their uses in adults and children.

What is Semaglutide and how does it work? 

Semaglutide is a Glucagon-Like Peptide-1 (GLP-1) receptor agonist, a medication that acts like a hormone called GLP-1, which is naturally made by the human body when you eat.

The hormone communicates with the brain to signal if you’re full. It also slows down how quickly food leaves the stomach, which makes you feel fuller for longer.

“So we may tend to feel fuller after a meal or for longer and therefore not have those signals that would trigger more eating,” says Punthakee, an associate professor with the department of Medicine and a member of the Centre for Metabolism, Obesity and Diabetes Research (MODR).

The drug is currently recommended for use in adult patients with a body mass index (BMI) of 27 who have at least one of the following related conditions: hypertension, Type 2 diabetes, dyslipidemia, or obstructive sleep apnea. It can also be prescribed for use in children 12 years of age and older.

There are several side-effects to taking the medication, including nausea, vomiting, constipation and diarrhea, Punthakee says.

Some people find the loss of appetite to be a negative side-effect — they don’t like the fact that they’ve lost their enjoyment of food, he says. “So some people will actually stop the medication because it’s working too well.”

How does the drug fit into the weight-loss equation with diet and exercise? 

There is a misconception that losing weight is as easy as eating less and working out, but the biochemistry in the brain plays a much bigger role in weight loss than most people think, Morrison notes.

“This is not a cognitive thing. This is all about the signals going to your brain saying you’re hungry,” says Morrison, a professor with the department of Pediatrics and the co-director of MODR.

“We have a sense that biology obviously varies from one person to another and some people have much stronger appetite drives than others do.”

Obesity is a chronic health condition, just like diabetes or hypertension. While it’s always preferred to treat obesity without drug interventions, that doesn’t always work, Punthakee says.

This is where medications like Wegovy can be beneficial, as it impacts the signals going to the brain and can disrupt the brain signals that tell your body it is still hungry.

Can these drugs be used to help children with obesity? 

Semaglutide has been approved for use in children 12 years of age and older, but there have been limited studies to evaluate the long-term impacts, Morrison says.

More research is needed, but if the drug were to be administered, it would be better used in adolescents with health issues, she says.

“My sense is if we’re going to use it, we would be focusing not on body size, but on the health aspects,” Morrison says. “The family would need to agree that this might be something that could improve the health of the child and then we would think about going ahead.”

Morrison is part of a group that is working on new clinical practice guidelines that will help clinicians and families make decisions about the best approach for them. The guidelines are expected later in 2024.

“The fundamental approach that we take is really trying to encourage families and kids to work on their healthy nutritional intake, regular physical activity, reduced screen time, good sleep and on their mental health as well.”

What is the long-term sustainability of these drugs? 

More research is needed to understand what happens when stopping these drugs and with long-term use, Morrison and Punthakee say.

“We have a lot to learn. We’ve got one year of data on kids. I don’t know the long-term impacts and I think it’s important that families understand that before they make this decision,” Morrison says.

And most research in adults has been done on the use of Semaglutide to treat people with diabetes, rather than for weight loss, Punthakee points out. But based on the evidence so far, there are no known harms, he says.

“In fact, studies have shown the medication can reduce heart attacks and strokes, while also being shown to reduce kidney complications from diabetes,” Punthakee says.

When patients stop using these weight-loss drugs they will also see a return of their appetite and may feel less full.

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