GLP-1 Receptor Agonists: Weight Loss and Side Effects

Beyond the number on the scale, bodies are changing, faces are transforming, and new reflections emerge: Is it safe? Is this treatment right for me? And if the weight loss happens too quickly, will my skin keep up?

In this article, we offer a clear and nuanced perspective on this phenomenon: what happens in the body, the possible effects on appearance, and ways to approach these transformations with balance.  

What are GLP-1 receptor agonists and how do they work? 

GLP-1 (glucagon-like peptide-1) is a natural hormone released by the intestine after a meal. Its role? To send signals to the pancreas and the brain to help the body properly manage food intake. 

This hormone acts on several levels: 

• It stimulates the secretion of insulin, a hormone that allows glucose (sugar) to move from the bloodstream into the cells, where it is used as an energy source. 
• It reduces the release of glucagon, a hormone that increases blood sugar levels. 
• It slows gastric emptying, which delays digestion and prolongs the feeling of fullness. 
• It acts on the brain to naturally reduce appetite. 

Result: you eat less, blood sugar remains more stable, and the body uses energy more efficiently. This combination of effects has made GLP-1 a major target in medicine, both for diabetes and weight management. 

Why are these medications prescribed? 

For type 2 diabetes 

GLP-1 receptor agonists were initially developed to help control blood sugar levels in people living with type 2 diabetes. They are often recommended when lifestyle changes (nutrition, physical activity) and first-line medical treatments (e.g., metformin) are no longer sufficient to maintain adequate glycemic control.

Some GLP-1 molecules also offer cardiovascular and renal protection. For individuals at risk, this can help reduce complications even when blood sugar is well managed. 

For weight management 

Over time, a significant effect on weight loss has also been observed. Some medications in this class are now approved in Canada to help adults who have: 

• a BMI of 30 or higher 
• a BMI of 27 or higher with a weight-related condition (such as hypertension, sleep apnea, high cholesterol, or diabetes) 

They are prescribed following a comprehensive medical evaluation and are part of a global approach that includes nutrition, physical activity, and sometimes psychological support. 

These treatments are approved by Health Canada, but they are not covered by public plans such as RAMQ when used for weight management. Cost may therefore be a barrier for some individuals. 

Some GLP-1 medications approved by Health Canada in 2025 

Several GLP-1 receptor agonists are approved by Health Canada. While they share a similar mechanism of action, they are not all indicated or equivalent for weight management. Treatment selection should always be made in collaboration with a physician, taking into account weight loss goals, overall health, budget, and insurance coverage.

Some treatments are approved for weight management (e.g., Wegovy, Zepbound, Saxenda, Rybelsus), while others are indicated for type 2 diabetes (e.g., Ozempic, Mounjaro, Victoza). Most of these medications are administered via subcutaneous injection, with frequency varying by product. 

Who should not take GLP-1 medications? 

These treatments are contraindicated in certain situations. They are generally not recommended if you have: 

• a personal or family history of medullary thyroid cancer or multiple endocrine neoplasia type 2 (MEN2) 
• current or past pancreatitis 
• gastroparesis (delayed gastric emptying) or inflammatory bowel disease 
• severe kidney disease (threshold varies depending on the molecule used) 
• pregnancy or plans to become pregnant in the near future 
• an allergy to these medications 
• are breastfeeding 
• diabetic retinopathy (for certain molecules) 

A complete medical evaluation is essential before starting this type of treatment. 

Possible side effects 

The most common side effects are digestive, especially at the beginning of treatment: 

• Nausea 
• Loss of appetite 
• Vomiting 
• Constipation or diarrhea 

These symptoms are often temporary and tend to subside over time. 

Other possible effects include: 

• Headaches 
• Dizziness 
• Injection site reactions 

In rare cases, the following have been observed: 

• Acute pancreatitis 
• Acute kidney failure 
• Severe allergic reactions 
• Gallbladder issues 
• Diabetic retinopathy 

Regular medical follow-up is essential to ensure proper tolerance. Dosage is individualized for each patient.