GLP-1 medicines have changed obesity treatment. Semaglutide, sold as Ozempic for type 2 diabetes and Wegovy for weight management, produced weight loss in trials that once seemed possible only with surgery. They also come with side effects, costs and trade-offs worth understanding, especially for people who care about keeping muscle.
- GLP-1 medicines mimic a gut hormone that reduces appetite, slows stomach emptying and improves blood sugar control.
- In trials, semaglutide for weight management produced average losses around 15 percent of body weight over more than a year.
- Common side effects are nausea, vomiting, diarrhoea and constipation; serious ones are rarer.
- Part of the weight lost is muscle, and weight tends to return after stopping.
How they work
GLP-1 (glucagon-like peptide-1) is released by the gut after eating. It tells the pancreas to release insulin when blood sugar is high, slows stomach emptying and acts on appetite centres in the brain. Natural GLP-1 lasts only minutes. Medicines such as semaglutide and liraglutide are modified to last much longer, which is why semaglutide can be injected once a week.
What results look like
In large trials of semaglutide for weight management, combined with lifestyle advice, people lost on average about 15 percent of their body weight over roughly 68 weeks, with wide variation between individuals. Liraglutide produced smaller average losses. Benefits included lower blood pressure, better blood sugar and, in a large cardiovascular trial, fewer heart attacks and strokes in people with heart disease and excess weight.
Side effects
- Digestive: nausea, vomiting, diarrhoea and constipation, especially when the dose is increased.
- Gallbladder: rapid weight loss raises the risk of gallstones.
- Pancreatitis: rare, but severe abdominal pain needs urgent care.
- Thyroid warning: rodent studies showed thyroid C-cell tumours; these medicines are not used in people with a personal or family history of medullary thyroid cancer or MEN2.
- Low blood sugar: mainly when combined with insulin or sulfonylureas.
The muscle question
When people lose a lot of weight quickly, part of it is lean mass. Studies of GLP-1 medicines found a meaningful share of the weight lost was lean tissue. Resistance training and enough protein are the most effective ways to protect muscle during any weight loss. See how to keep muscle while losing weight.
Anyone using a GLP-1 medicine should prioritise strength training two or three times a week and protein at every meal, even when appetite is low.
After stopping
Trials that stopped semaglutide found much of the lost weight returned within a year for many people, as appetite came back. These medicines are generally considered long-term treatments for a chronic condition, similar to blood pressure medication.
Getting them in Canada
GLP-1 medicines are prescription drugs. Semaglutide (Wegovy) and liraglutide (Saxenda) are approved for chronic weight management in Canada; coverage varies by provincial plan and private insurance. A doctor will consider your weight, health conditions and history. Products sold online as “research” or compounded versions are not equivalent to approved medicines and carry dosing and purity risks.
Who should be cautious
People with a history of pancreatitis, certain thyroid cancers, severe digestive disease, or who are pregnant or planning pregnancy need careful medical advice. People with eating disorders should not use them without specialist care.
Nutrition and fat lossHow to keep muscle while you lose weightRead guide
Frequently asked questions
Is Ozempic approved for weight loss in Canada?
Ozempic is approved for type 2 diabetes. Wegovy, the same molecule at different doses, is approved for chronic weight management.
Will I regain weight after stopping?
Many people regain much of it within a year. Lasting habits and, for some, long-term treatment help.
Do GLP-1 medicines cause muscle loss?
Some of the weight lost is lean mass. Strength training and protein reduce it.
Educational information only. Nothing here is medical advice or a recommendation to use any product. Anabolic steroids are Schedule IV under the Controlled Drugs and Substances Act. Talk to a doctor and get bloodwork before and after using any compound.
