If you’ve hit a plateau or aren’t losing weight on Mounjaro, don’t worry — you’re not alone, and there are a few common reasons why this might be happening. Diet, dosage, and lifestyle habits often play a key role. It’s also important to remember that Mounjaro takes time to fully kick in, especially as you work your way up to the optimal maintenance dose.
On average, people can lose up to 20% of their body weight after 72 weeks on the 15mg maintenance dose. But if your progress has stalled or you’re not seeing results, we’re here to help you get back on track. Let’s figure out what’s going on and map out the right next steps together. If you’re asking, “Why am I not losing weight on Mounjaro?”, there are multiple possible reasons to consider.
1. Inadequate Dosage or Insufficient Time on the Medication
Progressive dosing matters
Mounjaro is typically started at a low dose, usually 2.5mg per week, then gradually increased to minimise gastrointestinal side effects. Weight loss may not occur significantly at the lower doses. If you’re still on the starter dose or have only recently titrated upwards, your body might not yet be experiencing the full weight-loss potential of the drug.
Weight loss takes time
For many, meaningful fat loss begins after 8–12 weeks, especially once doses reach 10mg or 15mg weekly. Give the medication time to work through your system, especially if you’re only a few weeks in.
2. Eating More Than You Realise
The "I’m eating less" trap
Many users feel less hungry on Mounjaro, but portion size and food choices still play a massive role. Mounjaro doesn’t override poor eating habits. If your food intake is still energy-dense or carbohydrate-heavy, you might be in a calorie surplus despite reduced appetite.
Tracking your intake using apps like MyFitnessPal or Chronometer may reveal hidden sources of calories. Snacking, sugary drinks, and frequent “cheat meals” can all counteract the calorie deficit Mounjaro is meant to create.
Highly processed foods slow down results
Even if you’re eating less, processed foods (fast food, packaged snacks, white bread, sugary cereals) can stall weight loss. These cause insulin spikes, which interfere with fat burning, even while on Mounjaro.
3. Lack of Physical Activity
Medication isn’t magic
Mounjaro can help control appetite and improve insulin sensitivity, but physical activity remains essential. If you’re sedentary—spending most of your day sitting or lying down—you may be burning too few calories to see weight loss.
Muscle matters
If you’re losing fat but not maintaining muscle mass, the scale might not move much. Incorporating resistance training or bodyweight exercises can accelerate fat loss while maintaining lean mass, helping you look and feel leaner even if the weight loss seems slow.
4. Hormonal or Metabolic Conditions
Insulin resistance and metabolic syndrome
If you have severe insulin resistance or a metabolic disorder, your body may resist weight loss even with Mounjaro. The medication can help improve insulin function, but it might take longer to see changes.
Thyroid problems
Conditions like hypothyroidism slow down metabolism, making it harder to lose weight. If your weight isn’t shifting, request a thyroid function test to rule out any underlying conditions.
5. Not Drinking Enough Water
Hydration and fat metabolism
Water plays a crucial role in fat metabolism. Dehydration slows down the body’s ability to burn fat and can lead to water retention, which may mask fat loss on the scale.
Aim for at least 2–3 litres of water daily, especially if you experience constipation, a common side effect of GLP-1 agonists like Mounjaro.
6. Poor Sleep and High Stress Levels
Cortisol blocks fat loss
High stress increases cortisol, which contributes to belly fat accumulation and weight gain. If you’re not sleeping well or are under chronic stress, your body may hold on to fat despite Mounjaro.
Prioritise 7–9 hours of quality sleep, reduce screen time before bed, and practice stress-reducing activities like yoga, walking, or meditation.
7. Alcohol Consumption
Empty calories and metabolic disruption
Alcohol not only adds empty calories, but it also slows metabolism and impairs fat burning. Even moderate drinking can stall weight loss, especially when combined with high-fat or high-carb meals.
Limiting alcohol—or eliminating it—can improve the effects of Mounjaro significantly.
8. Gastrointestinal Side Effects Leading to Poor Nutrition
Nausea or food aversions may backfire
While some people eat less due to nausea or loss of appetite, others may lean on bland, carb-heavy foods like bread, crackers, or pasta. This coping mechanism can increase carb intake, which may slow or block weight loss.
Focus on protein-rich meals, healthy fats, and fibrous vegetables, even when nausea strikes.
9. Unrealistic Expectations
Fat loss vs. weight loss
Mounjaro promotes fat loss, not just water or muscle loss. Fat loss is slower but more sustainable. If you’ve lost inches or your clothes feel looser, you are likely losing fat but retaining lean mass, which is ideal.
Track your waist circumference, progress photos, and how clothes fit, not just your weight.
Comparing yourself to others
Some people lose 10kg in 3 months, others just 3kg in the same time. Individual biology, starting weight, adherence to healthy habits, and dose strength all vary. Don’t compare your journey to someone else’s highlight reel.
10. Mounjaro May Not Be the Right Medication for You
Everyone responds differently
Not everybody responds the same way to GLP-1/GIP receptor agonists. If you’ve been on Mounjaro for more than 16 weeks at a therapeutic dose (e.g. 10mg or 15mg) and have seen no significant weight loss, discuss alternatives with your doctor.
Other medications like Wegovy, Saxenda, or Nevolat might work better for your specific metabolic profile.
Tips to Maximise Weight Loss on Mounjaro
- Stick to high-protein, low-carb meals.
- Track calories, especially during weekends or social meals.
- Avoid alcohol and sugary drinks.
- Incorporate strength training 2–3 times per week.
- Walk daily, even for 20–30 minutes.
- Monitor non-scale victories like clothing fit, photos, and energy levels.
- Be patient and consistent.
When to Consult Your Doctor
- If you haven’t lost any weight after 12–16 weeks on the therapeutic dose
- If you experience side effects that prevent you from eating healthily
- If you suspect a thyroid or metabolic disorder
- If you're unsure whether you're taking the medication correctly
A personalised medical evaluation can help you determine if dose adjustments, blood tests, or switching medications are necessary.
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Uzma Aslam
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Mohammed Ismail Lakhi
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Muhammed Luqman Asghar
