Why am I not losing weight on Mounjaro?

Whether you’re taking Mounjaro (tirzepatide) to manage your type 2 diabetes or to lose weight (or both), you’re probably expecting some sort of weight loss. So, if you’re not noticing any changes on the scale, you might be asking yourself, “why am I not losing weight on Mounjaro?”

Maybe you recently started Mounjaro and the pounds aren’t slipping away quite as quickly as you thought they would. Or maybe you’ve been taking Mounjaro for a while, but it feels like your weight loss has slowed down to a snail’s pace.

Whatever the case may be, there could be a number of explanations for why you’re not losing weight on Mounjaro. Read on as we explore common reasons behind slower weight loss on Mounjaro and what to do if Mounjaro isn’t working for you.

The weight loss effects of Mounjaro kick in pretty quickly. In one clinical trial, people lost an average of 6% of their body weight after just two months of using Mounjaro. After six months, they had lost between 12–14% of their body weight, depending on the dosage they were taking. After a year and a half, they had lost between 15%–21%. 

However, it’s important to note that these results are averages. The amount of weight loss you experience on Mounjaro can depend on a variety of factors, including your current health situation, diet, exercise routine, and the dosage you’ve been prescribed.

It’s also worth mentioning that Mounjaro is not approved for weight loss by the U.S. Food and Drug Administration (FDA). Mounjaro is a prescription medication that treats type 2 diabetes by controlling blood sugar levels. However, because it also tends to produce significant weight loss, health providers may prescribe Mounjaro off-label for weight loss. 

If you’re not losing as much weight as you expected to on Mounjaro, a number of factors could be at work. Consider if any of the reasons below could be contributing to your weight loss (or lack thereof) on Mounjaro.

1. You may need to change up your diet or exercise routine

Mounjaro works best when used with lifestyle changes such as diet and exercise, which go hand-in-hand when it comes to successful weight loss. Following a well-balanced diet can help you consume fewer calories, which, along with exercise, can help you maintain a calorie deficit (i.e. eating fewer calories than you burn)—an essential component of weight loss. It can also help you incorporate certain weight loss-promoting foods, such as those high in protein and fiber. 

If you read that and thought, “easier said than done,” we hear you. Cutting calories and reworking your eating plan doesn’t always feel easy (or, let’s be real, fun). But it can be easier when you combine it with other dietary strategies, such as:

• Eating fewer empty calories (e.g. processed foods, sweets, and snacks)

• Eating only when you’re hungry (and stopping once you’re full)

• Practicing portion control

• Avoiding eating during other activities, such as watching television or driving

Like diet, regular exercise plays a major role in preventing weight regain and maintaining a healthy weight in the long run. Exercise also helps you preserve muscle, which is critical to keeping your metabolism working at its best. In particular, strength training—think: weight lifting, using resistance bands, and even yoga—helps to build muscle mass, burn fat, and increase your metabolism. 

Exercise of any kind can be helpful to weight loss, but combining aerobic and resistance exercise seems to drive the biggest results. So, if you’re only doing aerobic or resistance workouts, add in one of the other. And if you have the energy and the time, consider if you can add in even more exercise to your weekly routine. While 150 minutes of physical activity per week is the commonly touted baseline for good health, experts recommend bumping it up to 200–420 minutes if your goal is to lose weight and keep it off.

2. You’ve hit a weight loss plateau

If you were losing weight on Mounjaro at a consistent pace, but now it feels like things suddenly screeched to a halt, you may have hit a weight loss plateau. Not to worry; this is a normal and often expected part of the weight loss journey, whether or not you’re taking Mounjaro.

Put simply, our brains are trained to keep our bodies alive. One way they do that is by holding on to fat and energy so we stay at a so-called “set point.” When we start losing weight—whether through diet, exercise, a medication like Mounjaro (or all of the above)—it takes time for our brains to catch up and realize we are losing weight because we are eating less. When it does, our brain slows down our metabolism to prevent us from starving. In times of famine, this is a helpful adaptation. But when you’re trying to lose weight, it turns into an unhelpful weight loss plateau. 

When you reach a plateau, you may not have to do anything different. Just keep up with your diet and exercise routine, and try not to get too frustrated in the meantime. Your brain should adjust to the new normal, and you’ll start losing weight again soon. 

But if it’s been a few weeks and you still feel stuck, you may need to make a few changes. Reevaluate whether your current habits are helping you lose weight or if any of them might be disrupting your progress. Here are some ideas to get you started:

• Ensure you’re following a balanced diet by tracking what you eat with a food journal. 

• Track alcohol consumption, as this can be a common culprit of empty calories. 

• Build muscle by eating more protein and upping your strength workouts. 

• Move more throughout the day (e.g. using the stairs instead of the elevator, getting up every half hour to move around or stretch, and parking further away so you can walk a bit farther).

3. You have other health conditions

Every body responds differently to medication, and one factor that can affect weight loss on Mounjaro is your current health situation. Underlying medical conditions and other medications you are taking can play a role in how quickly you lose weight on Mounjaro.

For example, polycystic ovarian syndrome (PCOS) is associated with weight gain and may slow weight loss on Mounjaro. And research shows that people with type 2 diabetes tend to lose less weight on medications like Mounjaro than people without diabetes. In studies of tirzepatide (the active ingredient in Mounjaro), people with type 2 diabetes lost around 13–15% of their body weight in a year and a half on the higher dosage strengths of Mounjaro. In a separate study of people without diabetes, participants lost 19–21% of their body weight in the same time period on the same dosage strengths.

In other studies, people with type 2 diabetes who only took Mounjaro to control their blood sugar levels lost 6–8% of their body weight after ten months. Those who were also taking another diabetes medication called metformin, however, lost between 7–11% in the same time period.

While some medications can encourage even more weight loss like Mounjaro, others can cause weight gain, including:

• Antipsychotics and mood stabilizers

• Antidepressants

• Some medications that treat high blood pressure

• Diabetes medications

• Contraceptive (birth control) medications

• Corticosteroids

• Antihistamines

4. You’re too stressed out or sleep-deprived

Other lifestyle factors, from sleep to stress, can lead to weight gain and slow weight loss on Mounjaro. Both getting too little (less than 6 hours per night) as well as too much sleep (more than 8 hours per night) can lead to weight gain. Regularly sleeping less than 6 hours per night disrupts appetite hormones, increasing your subjective hunger — particularly for high-calorie foods, such as those high in refined carbohydrates. In general, you should aim for a healthy balance of 6–8 hours per night.

Poor sleep habits can also intensify stress, which itself is linked to weight gain. People who experience significant stressful life events—such as a divorce or financial loss—as well as those who feel more stressed on a day-to-day basis are more likely to gain weight and belly fat. Stress can contribute to weight gain by interfering with hormone levels. It can also cause weight gain in more straightforward ways, such as not having the time or the energy to cook healthy food and work out. 

5. You need a higher dosage of Mounjaro

Mounjaro comes in six dosage strengths: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg. Typically, health providers prescribe a starting dosage of 2.5 mg before gradually increasing your dosage over a period of weeks until they find an effective dosage that produces the desired results, all while keeping Mounjaro’s side effects manageable. 

Weight loss results tend to be more pronounced on the higher doses of Mounjaro in people both with and without type 2 diabetes. For example, after a year and a half, people without type 2 diabetes lost 15% of their body weight on the 5 mg dosage, 19.5% on the 10 mg dosage, and 20.9% on the 15 mg dosage. In the same time period, people with type 2 diabetes lost 12.8% on the 10 mg dosage, and 14.7% on the 15 mg dosage.

If your weight loss has slowed down, it is possible that you need a higher dosage of Mounjaro. Talk to your healthcare provider if you think this might be the case.

6. You’re not taking Mounjaro as prescribed

Finally, if you’re not seeing the weight loss you expected with Mounjaro, the reason why could be as simple as not taking it as prescribed. Mounjaro should be injected once a week, on the same day each week. 

Ideally, you should never miss a dose of Mounjaro. If you do, it’s not the end of the world, but be aware that it can lead to side effects and disrupt the progress you’ve experienced on Mounjaro. Tirzepatide, the active ingredient in Mounjaro, has a half-life (i.e. how long a drug stays in your system) of five days, so if you don’t take it consistently, the effects—including decreased appetite—may not be as pronounced because there’s not enough of it in your body.

Mounjaro is an effective medication that treats type 2 diabetes and can lead to sustainable weight loss for many people. In one large clinical trial, up to 91% of people lost at least 5% of their body weight over the course of a year and a half. That’s amazing. However, that also means that almost 10% of people did not experience that amount of weight loss. If you think you might be one of those people, you have options.  

If you recognize yourself in any of the explanations we listed above, implement some healthy lifestyle changes to see if they recharge your weight loss efforts. For example, you might:

• Improve your sleep hygiene

• Reduce your stress levels

• Make healthier food choices

• Start or add to your workout routine

• Get treatment for your other underlying health conditions

If Mounjaro isn’t working for you, talk to your healthcare provider. It’s possible you may need a higher dosage of Mounjaro. Or you may need to try a Mounjaro alternative like Zepbound (tirzepatide), Ozempic (semaglutide), Wegovy (semaglutide), or Saxenda (liraglutide). There are several medications available, some of which are approved for weight loss while others are prescribed off-label for weight loss. One may be a better fit for you over another.

You can also try a comprehensive weight loss program like Ro Body, which includes a prescription for an injectable weight loss medication along with personalized coaching to help you meet your weight loss goals.

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How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

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Current version

April 30, 2024

Written by

Amelia Willson

Fact checked by

Raagini Yedidi, MD

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About the medical reviewer

Raagini Yedidi, MD

Raagini Yedidi, MD, is an internal medicine resident and medical reviewer for Ro.