The simple version
When you eat, your gut releases a hormone called GLP-1 (glucagon-like peptide-1). This hormone does three things: tells your brain you're full, slows digestion so food stays in your stomach longer, and helps regulate blood sugar. In people with obesity, these natural signals may be weakened or overwhelmed.
GLP-1 medications are synthetic versions of this hormone, engineered to last much longer in the body (about 7 days vs minutes for the natural hormone). They amplify the signals your body already uses — you feel less hungry, get full faster, eat less, and lose weight. Many patients describe it as "food noise" disappearing — the constant background thinking about food simply quiets down.
GLP-1 medications available in Australia
| Medication | Active ingredient | Type | Avg. weight loss | Status |
|---|---|---|---|---|
| Mounjaro | Tirzepatide | GLP-1 + GIP dual agonist | ~21% | Available |
| Wegovy | Semaglutide 2.4mg | GLP-1 agonist | 15–17% | Available |
| Ozempic | Semaglutide 1mg | GLP-1 agonist | ~15% | Diabetes only |
How do they differ from older weight loss drugs?
Older medications like Duromine (phentermine) work as stimulants that suppress appetite through the central nervous system. They're effective short-term but limited to 12 weeks due to tolerance and cardiovascular risks. Contrave targets the brain's reward pathways.
GLP-1 medications work through a completely different — and far more effective — mechanism. By mimicking natural gut hormones, they produce 2–4 times more weight loss than older drugs, can be used long-term, and have additional health benefits including cardiovascular risk reduction and improved blood sugar control.
What about Mounjaro? Is it a GLP-1?
Mounjaro (tirzepatide) is technically a dual GLP-1/GIP agonist — it targets two gut hormone receptors instead of one. The GIP (glucose-dependent insulinotropic polypeptide) pathway appears to enhance fat metabolism and energy expenditure beyond what GLP-1 alone achieves. This dual action likely explains why Mounjaro produces more weight loss (~21%) than pure GLP-1 medications like Wegovy (~15-17%).
Common side effects
The most common side effects are gastrointestinal: nausea, diarrhoea, vomiting, and constipation. These typically occur during dose escalation (the first few months as doses increase) and improve as your body adjusts. Most patients find them manageable, especially with smaller meals and adequate hydration.
Check side effects by medication →
Are they safe long-term?
Semaglutide has been studied for up to 4 years of continuous use with a reassuring safety profile. The SELECT trial (17,604 participants) actually showed Wegovy reduces cardiovascular events by 20% — making it protective for heart health. Tirzepatide has 2 years of data so far. All GLP-1 medications require ongoing medical monitoring.
How to access GLP-1 medications in Australia
You need a prescription from a doctor (GP or telehealth). Eligibility requires BMI ≥30 (or ≥27 with a health condition). Multiple telehealth providers prescribe GLP-1 medications with delivery to your door.