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Why am I not losing weight on Mounjaro?
Progress with Mounjaro can vary from person to person, and not seeing immediate results does not necessarily mean the treatment is ineffective. Many lifestyle, physiological and treatment-related factors can affect weight-loss outcomes, and a healthcare professional can provide personalised assessment and guidance.
What is Mounjaro?
Mounjaro is a prescription weight-loss injection containing tirzepatide, which works by mimicking two gut hormones, GLP-1 and GIP, to reduce appetite, slow gastric emptying and improve blood sugar regulation. It is licensed for adults with obesity or overweight and related health risks, particularly where lifestyle measures alone have not achieved sufficient results. While it has shown to help weight loss, showing weight reductions of up to 20% over long-term use, understanding that Mounjaro supports weight loss rather than replaces healthy habits is essential when deciding whether treatment is suitable.
Reasons you're not losing weight on Mounjaro
Diet
Mounjaro can make it easier to eat less but portion sizes, food choices and eating patterns still matter. Diets low in protein may lead to faster hunger return and muscle loss, while low fibre intake can reduce satiety and gut health. Highly processed or energy-dense foods can quietly add calories even when overall appetite feels reduced. Alcohol provides empty calories with little nutritional value and can weaken appetite control and decision-making around food. A balanced intake with adequate protein, vegetables, whole grains and fluids helps the medication work more effectively.
Exercise
Physical activity supports weight loss in several ways beyond simply burning calories. Resistance and weight-bearing exercise help build muscle which helps maintain resting metabolic rate as body weight falls. Without this, the body may adapt by using fewer calories overall, slowing progress. Cardiovascular activity improves insulin sensitivity and cardiovascular health boosting the metabolic effects of Mounjaro.
Sleep
Sleep plays a central role in weight regulation. Short or disrupted sleep increases ghrelin (the hunger hormone) and reduces leptin (the hormone that signals fullness), making appetite harder to control even with medication. Poor sleep is also associated with reduced insulin sensitivity and higher blood glucose levels, which can blunt the metabolic benefits of Mounjaro. Establishing regular sleep routines and aiming for sufficient rest can noticeably improve weight-loss response.
Stress
Chronic stress can undermine progress through both physiological and behavioural pathways. Elevated cortisol levels are linked to increased appetite, preference for high-calorie foods and greater fat storage, particularly around the abdomen. Stress can also reduce motivation, disrupt sleep and make it harder to maintain consistent eating and activity habits.
Weight loss plateau
Plateaus are a normal part of any weight-loss journey. As weight decreases, energy requirements fall and the body becomes more efficient, which can temporarily halt further loss. This does not indicate that Mounjaro has stopped working.
Low dosage
Mounjaro treatment begins at low doses to minimise side effects and allow the body to adapt. These starter doses are not intended to produce maximum weight loss. More substantial appetite suppression and metabolic effects are typically seen at higher maintenance doses, which are reached gradually over time. Remaining on a lower dose for a short period with minimal weight change is therefore expected and should not be interpreted as treatment failure.
Key takeaways
- Adjust your diet: Start tracking your calories in a notebook or an app. Try to eat more fibre and protein and make sure to drink plenty of water to stay hydrated.
- Find a physical activity that you like to do: Exercise is work and it is easier to put it off when it’s something you hate doing. Try a dance class, go on a hike, get your friends involved.
- Improve your sleep routine: Reduce your screen time before bed and try to get 7-9 hours of sleep each night.
- Reduce stress: Try meditation or set aside some time for relaxation or a hobby that you love to let yourself unwind.
- Be patient and kind to yourself: Losing weight is not a quick process. Understand that a plateau are a normal part of the process.
- Low dosage: Speak with your doctor or pharmacist about the next step in your treatment.