Ozempic, Mounjaro, Wegovy and Saxenda have transformed what is pharmacologically achievable in weight management. This is the complete Australian guide — how they work, what the clinical trial data actually shows, realistic costs, side effects, and critically, what happens to your body — including your skin — as the weight comes off.
Close-up of a person's hands holding a GLP-1 injection pen, or a warm editorial-style image of someone in a pharmacy consultation. Clinical yet approachable. Not graphic.
GLP-1 (glucagon-like peptide-1) is a hormone your gut produces naturally after eating. It signals fullness, slows digestion, and stimulates insulin release. GLP-1 receptor agonists amplify and extend this signal — producing effects that go far beyond what the natural hormone achieves.
The result is a dramatic reduction in appetite — many patients describe the near-elimination of what researchers call "food noise" — alongside measurable improvements in blood glucose control, cardiovascular risk markers, and body composition when combined with adequate protein intake and activity.
Newer agents like tirzepatide (Mounjaro) add GIP receptor agonism on top of GLP-1 action, producing synergistic effects that explain why its average weight loss outcomes significantly exceed those of semaglutide.
These medications are remarkably effective tools. They are not a complete solution on their own. Without adequate protein intake, they accelerate muscle loss alongside fat loss. Without dietary support, plateau management is difficult. Without understanding what happens to your skin after significant weight loss, the outcome may not match expectations. All of this is covered here.
GLP-1 receptors in the hypothalamus and brainstem are activated, reducing hunger signals and food-seeking behaviour. Most patients report a significant reduction in appetite within days to weeks of starting.
Food moves more slowly from the stomach into the small intestine — extending the sensation of fullness after meals and reducing post-meal glucose spikes. This is also the reason GLP-1 medications require management before surgery.
Insulin is stimulated only when blood glucose is elevated — significantly reducing hypoglycaemia risk compared to older diabetes medications, and making these agents safer for a broader population.
Mounjaro adds GIP receptor agonism — working synergistically with GLP-1 pathways to produce greater appetite suppression and energy expenditure. This dual action explains the superior efficacy data compared to semaglutide.
How GLP-1 receptor agonists act on the brain (appetite suppression), stomach (delayed emptying) and pancreas (glucose-dependent insulin release). Tirzepatide adds GIP receptor action for synergistic effects. Clinical illustration — myweightlossjourney.com.au.
All figures are from published Phase 3 clinical trial programmes. Real-world results vary. Costs are indicative for Australia as at mid-2026 and subject to change — confirm current pricing and PBS status with your prescriber.
| Medication | Active compound | Receptor target | Dosing | Avg weight loss | TGA approved for weight | PBS subsidised | Approx. monthly cost (AU) |
|---|---|---|---|---|---|---|---|
| Ozempic | Semaglutide 0.5–2mg | GLP-1 | Weekly injection | ~9–15% | T2DM only (weight off-label) | Yes (T2DM) | $31–42 (PBS) / $150–200 private |
| Wegovy | Semaglutide 2.4mg | GLP-1 | Weekly injection | ~14.9% | Yes — weight management | No | $269–390 private |
| Mounjaro ★ | Tirzepatide 2.5–15mg | GLP-1 + GIP dual | Weekly injection | Up to 22.5% | Yes — T2DM & weight | No | $285–690 private |
| Saxenda | Liraglutide 3mg | GLP-1 | Daily injection | ~8.4% | Yes — weight management | No | $350–450 private |
★ Mounjaro has the highest average weight loss of any approved medication. PBS status and availability change — always confirm current status with your prescriber. Costs shown are approximate private-pay figures as at mid-2026.
Average body weight reduction over 24 months across all weight loss pathways. Based on Phase 3 clinical trial data. Individual outcomes vary significantly. Shaded zone indicates the weight stability window that triggers body contouring eligibility. — myweightlossjourney.com.au.
What to expect at each stage of treatment, the side effects that matter, and the specific considerations for Australian patients.
Mounjaro is a dual GIP/GLP-1 receptor agonist — the first of its class to reach approval. By simultaneously activating both GIP and GLP-1 receptors, it produces weight loss outcomes that significantly exceed any single GLP-1 agonist in head-to-head trial data. The SURMOUNT programme established it as the current standard for pharmacological weight loss efficacy, and the 2025 SURMOUNT-5 head-to-head trial confirmed tirzepatide's superiority over semaglutide directly. In Australia, Mounjaro is TGA-approved for both type 2 diabetes management and chronic weight management. It is available on private prescription — it is not PBS-subsidised for either indication, with costs starting at approximately $285/month for the initiation dose and rising to $550–690/month at maintenance doses.
Wegovy and Ozempic contain the same molecule — semaglutide — at different approved doses and for different indications. Ozempic (up to 2mg) is approved for type 2 diabetes and has the most extensive real-world cardiovascular safety data of any GLP-1 medication. Wegovy (2.4mg) is specifically approved for chronic weight management. The SELECT trial established semaglutide's cardiovascular benefit — a 20% reduction in major adverse cardiovascular events in patients without diabetes — a landmark finding that extends the clinical significance of this class beyond weight loss alone.
Saxenda contains liraglutide — the same molecule used at lower doses in Victoza for type 2 diabetes. At 3mg daily it is specifically approved in Australia for chronic weight management, making it one of only two on-label weight management options (alongside Wegovy). It requires daily rather than weekly injection, and produces lower average weight loss than semaglutide or tirzepatide, but carries the longest established safety record of any GLP-1 for weight management and may suit patients who prefer a daily dosing schedule or who have not tolerated weekly agents.
This is the most important question — and the one most GP appointments don't address adequately.
The clinical trial data on GLP-1 cessation is consistent: most patients regain a significant proportion of lost weight after stopping medication, particularly without structured dietary and lifestyle support. The STEP 4 withdrawal trial showed that patients who stopped semaglutide after 20 weeks regained approximately two-thirds of their lost weight within 12 months.
This does not mean GLP-1 medications are not worthwhile. It means they work best as part of a longer-term strategy — not a finite course. And it means that the dietary habits, protein intake targets and resistance training routines established during medication use are the primary determinants of long-term outcome after stopping.
Weight must be stable for a minimum of 3–6 months before body contouring assessment. This means reaching a genuine plateau — not still actively losing weight at a slower rate. Contact our team to discuss timing when you approach this milestone.
Dietary habits established during GLP-1 use are the primary mechanism of maintenance after stopping. Structured support from Amy Kellner APD should begin while still on medication, not after ceasing it.
GLP-1 medications suppress appetite dramatically. Without resistance training and adequate protein, a significant proportion of weight lost is muscle, not fat. Muscle mass drives metabolic rate and prevents weight regain.
High protein intake (1.6–2.2g per kg body weight) supports muscle retention, satiety and long-term weight maintenance. This is especially important during GLP-1 use when total caloric intake is significantly reduced.
For patients with significant loose skin after GLP-1-mediated weight loss, body contouring surgery removes a significant psychological and physical barrier to long-term weight maintenance. Completing the transformation matters.
The GLP-1 class is moving faster than any drug category in recent memory. Several next-generation agents are in late-stage trials that may significantly change the weight loss pharmacology landscape by 2027. This section reflects the best available evidence as at mid-2026 — indications, approval timelines and Australian availability will evolve.
A once-weekly injection combining semaglutide (GLP-1 agonist) with cagrilintide, a synthetic amylin analogue. Amylin is a pancreatic hormone that complements GLP-1 signalling — the combination targets appetite and energy balance through separate, additive pathways. FDA approval was filed in December 2025. Phase 3 data showed average weight loss of approximately 22.7% of body weight over 68 weeks in the REDEFINE 1 trial.
The first triple receptor agonist — simultaneously activating GLP-1, GIP and glucagon pathways. Glucagon receptor activation increases energy expenditure directly, which explains why early Phase 2 data showed weight loss approaching bariatric surgery outcomes in some patients. Currently in Phase 3 TRIUMPH trials. If these results are confirmed, retatrutide may become the most potent pharmacological weight loss agent available.
The most patient-friendly development in the GLP-1 class — a once-daily tablet. Unlike existing oral semaglutide (Rybelsus), orforglipron is a small non-peptide molecule that does not require fasting restrictions and can be taken at any time of day with food. FDA review is ongoing with a decision expected by mid-2026. Australian availability is estimated 2027 if approved. For the estimated 25% of patients who are needle-averse, this may be the option that brings GLP-1 therapy within reach.
Where CagriSema combines two separate drugs, amycretin fuses GLP-1 and amylin activity into a single molecule. Early Phase 1/2 data — published in The Lancet — showed approximately 22% body weight loss in 36 weeks, which is remarkable efficacy for such an early trial. Novo Nordisk advanced amycretin directly into Phase 3 development in 2025. If Phase 3 confirms these numbers, it may challenge both CagriSema and tirzepatide as a first-line option.
All figures are from published Phase 2 or Phase 3 trial data. Emerging agents show Phase 2 or early Phase 3 results — final outcomes may differ. Individual results vary. This information reflects the evidence base as at mid-2026 and will be updated as new data emerge. This page does not constitute prescribing advice — all medication decisions should be made with a qualified prescriber.
If you are taking a GLP-1 medication and planning body contouring surgery, there are specific considerations that must be addressed with Dr Kumar's team well in advance of your procedure date.
GLP-1 medications significantly delay gastric emptying — the same mechanism responsible for their satiety effect. Under general anaesthesia, this increases aspiration risk. Anaesthetic bodies and the TGA recommend pausing GLP-1 medications before elective surgery. Timing varies by agent and clinical situation.
Body contouring surgery is planned around a stable body weight. Operating while weight is still declining — even slowly — produces results that change as further weight loss occurs after surgery. Plan to reach your realistic long-term weight before booking a surgical assessment with Dr Kumar.
Patients who have lost significant weight on GLP-1 medications often have suboptimal nutritional status — protein deficits, micronutrient deficiencies, reduced muscle mass. Amy Kellner APD's pre-surgical protocol corrects these in the months before surgery, significantly improving outcomes and healing capacity.
Amy Kellner APD specialises exclusively in weight loss and surgical patients. Her approach to GLP-1 nutrition management — protein preservation, satiety optimisation, muscle maintenance and long-term habit building — significantly improves both weight loss outcomes and body composition compared to medication alone.
Amy Kellner in a warm, professional setting — could be reviewing nutrition plans, telehealth consultation, or meal preparation context. Approachable, expert, relatable.