Dr Nick Fuller
Leading Obesity Expert at the University of Sydney and founder of Interval Weight Loss.
Mounjaro (tirzepatide) is making headlines for its impressive weight loss results. In clinical trials, some people lost over 22% of their total body weight. That’s more than most diet or exercise programs achieve on their own. For example, someone weighing 100 kg at the start could lose more than 20 kg over time, if they respond well to treatment.
But how much weight can you expect to lose on Mounjaro? The answer depends on your dose, your lifestyle, and individual factors like age and health conditions.
Mounjaro (tirzepatide) is part of a newer class of medications called GLP-1/GIP receptor agonists. These drugs copy the effects of natural gut hormones that help control appetite, digestion and blood sugar levels. Where older treatments usually target just one hormone pathway, Mounjaro activates two (GLP-1 and GIP), giving it a unique dual action.
GLP-1 slows down how quickly food leaves your stomach, curbs appetite and reduces cravings. At the same time, glucose-dependent insulinotropic polypeptide or GIP appears to boost insulin sensitivity and may amplify the benefits of GLP-1, making the combination more effective for both weight management and blood sugar control.
Clinical trials back this up. In the SURPASS-2 trial, people taking tirzepatide lost significantly more weight than those on semaglutide, another popular GLP-1 injection. Researchers believe this ‘double hit’ on appetite and metabolism is what sets Mounjaro apart, helping people achieve greater and more sustained results.
Weight loss on Mounjaro doesn’t happen overnight. The dose is slowly increased so your body can adjust, and results become more noticeable over time. Instead of thinking week by week, it’s better to look at progress across months, as that’s how clinical trials measure outcomes.
First 1–3 months – Early weight loss begins as your appetite decreases and digestion slows. People may notice a few kilos lost, but this stage is more about adjusting to the medication.
Week 40 – By this stage, weight loss becomes more noticeable. In the SURPASS?2 trial, participants with type 2 diabetes lost approximately 7–13% of their body weight over 40 weeks, depending on the tirzepatide dose, with higher doses producing the greatest reductions.
Week 72 – Weight loss becomes more pronounced during this period. In the SURMOUNT?1 trial, most participants, including those who were slower to respond initially, achieved significant reductions in body weight. By Week 72 (about 17 months), 90% of late responders had lost at least 5% of their body weight, and overall participants without diabetes lost approximately 15–21% of their body weight, with higher doses producing the greatest reductions. This shows that continuing treatment beyond the early months can help more people reach meaningful weight loss goals.
1 year and beyond – Real-world data comparing tirzepatide and semaglutide show that after 12 months, people on tirzepatide lost an average of 17.2 kg (16.5% of body weight), while those on semaglutide lost 14.6 kg (14.1%). Both medications led to significant, clinically meaningful weight loss, confirming that these results translate outside of clinical trials.
Lifestyle habits, health conditions, and even stress or sleep can influence how well Mounjaro works for you. Let’s look at the main factors that shape results.
Food choices make a huge difference in whether you maximise results or stall progress. Pairing Mounjaro with a nutrient-rich diet helps you maintain energy and support long-term health. Here’s what to focus on and what to limit.
What to Eat
Lean proteins (chicken, fish) – Keep you full while supporting muscle maintenance.
Fresh fruits and vegetables – Provide fibre, vitamins, and antioxidants.
Whole grains (brown rice, oats) – Deliver slow-release energy to keep you satisfied.
Healthy fats (avocado, nuts) – Help balance hormones and promote satiety.
Legumes and beans – Offer plant-based protein and fibre for gut health.
Plenty of water – Keeps digestion smooth and reduces bloating.
What to Avoid
Processed foods – Often high in calories, low in nutrients.
Sugary snacks and desserts – Cause blood sugar spikes and cravings.
Refined carbs (white bread, pasta) – Lead to quick energy crashes.
Fried foods – Pack in excess fat and calories.
High-sodium packaged meals – Contribute to water retention and bloating.
Sugary sodas and sweetened drinks – Add empty calories and disrupt weight loss.
Movement supercharges the benefits of Mounjaro by burning calories, improving metabolism, and supporting heart health. A mix of cardio, strength and flexibility training gives the best results. Try including:
Walking – Simple, accessible, and effective for daily movement.
Jogging – Boosts cardiovascular health and calorie burn.
Cycling – A joint-friendly way to build endurance.
Swimming – Full-body workout that’s easy on the joints.
Strength training – Builds muscle, which increases metabolism.
Yoga – Improves flexibility and lowers stress levels.
Pilates – Strengthens core muscles and posture.
HIIT workouts – Short, intense sessions for maximum calorie burn.
Younger adults often lose weight faster due to a naturally higher metabolism. Older adults may see slower progress but still benefit from consistent, sustainable losses. Age influences results, but healthy habits remain powerful at every stage of life.
Certain medical conditions can impact how much weight you lose on Mounjaro. For example, people with type 2 diabetes may see improvements in blood sugar before major weight changes. Here are some conditions that can affect outcomes:
Type 2 diabetes – Improves glucose control but may slow weight loss at first.
Thyroid disorders – Can alter metabolism, affecting results.
Polycystic ovary syndrome (PCOS) – Linked to weight gain but may improve with treatment.
Gastrointestinal issues – May cause side effects or limit tolerance.
Cardiovascular disease – Requires careful monitoring during treatment.
Kidney problems – Can affect medication clearance and safety.
Depression or anxiety – May influence eating habits and weight changes.
Hormonal imbalances – Can make weight regulation more challenging.
Good sleep keeps hunger hormones balanced and supports steady weight loss. Poor sleep, on the other hand, increases cravings for high-calorie foods. Aim for 7–9 hours per night to give your body the best chance at progress.
High stress levels increase cortisol, which promotes fat storage around the belly. Stress can also trigger emotional eating, undoing your calorie deficit. Stress management techniques like meditation, journaling or gentle exercise can help.
Mounjaro’s effectiveness depends on sticking to the prescribed dosing schedule. Higher doses usually bring greater weight loss, but they also increase the chance of side effects. Your doctor will guide you through gradual increases for safe, steady progress.
So, how much weight can you lose on Mounjaro? Clinical trials show up to 22% body weight reduction over time, especially at higher doses with consistent use. But your personal results will depend on diet, exercise, age, health conditions, sleep and stress levels.
The bottom line: Mounjaro is a powerful tool, but it works best when paired with healthy habits and guided by medical supervision. If you’re ready to explore it, talk to your doctor about whether it’s the right fit for you.
Dr Nick Fuller is the founder of Interval Weight Loss and is a leading obesity expert at the University of Sydney with a Ph.D. in Obesity Treatment. Dr Fuller is also the author of three best-selling books and his work been published in top ranked journals in the medical field, including JAMA, Lancet and American Journal of Clinical Nutrition.