Around half a million Australians use GLP-1 medications for diabetes – and when you add people who use it for obesity and weight-related conditions, the total is much higher.

GLP-1s – such as semaglutide (Ozempic or Wegovy) and tirzepatide (Mounjaro) – are very effective at managing diabetes, obesity and metabolic or weight-related health conditions.

But they can come with gastrointestinal and other side effects, including nutritional deficiencies.

If you’re taking a GLP-1, here’s what you need to know about possible side effects and how to get enough nutrients as your food intake decreases.

How do these medicines work?

When you eat, your body makes the appetite hormones GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide).

These hormones affect:

how hungry and full you feel

how quickly your food passes through your intestines

blood sugar regulation

metabolic rate and energy expenditure

the brain’s reward centre, which impacts whether foods feel satisfying to eat, or not.

When our body produces these hormones, they only remain active for a few minutes.

But medications containing manufactured GLP-1 and GIP are modified to resist being broken down. This is why these medications, known as GLP-1 and GIP receptor agonists, only need to be injected weekly.

How much weight do users lose?

Compared to placebo (dummy) medications, average weight losses are about 6.24 kilograms higher in adults with type 2 diabetes or obesity who received semaglutide (1mg weekly), and up to 10.8kg greater for tirzepatide (15mg weekly).

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