Mounjaro (tirzepatide) outperforms the other diabetes drugs used for weight loss. That includes metformin, liraglutide and semaglutide (Ozempic or Wegovy). It is the most effective weight-loss drug studied so far. It copies two gut hormones, GLP-1 and GIP. Earlier drugs of this type, like liraglutide and semaglutide, copy GLP-1 alone.
Summary: Early studies show that many diabetes drugs also work for weight loss. They lower insulin resistance and act on gut hormones called incretins. That slows digestion and cuts appetite. One of these incretin drugs, Ozempic, is already widely used for weight loss. But now studies show that a newer diabetes drug, Mounjaro, works even better than Ozempic. In fact, it seems to be the most effective drug for weight loss.
Obesity and metabolic disorders are often closely tied to diabetes. Obesity raises the risk of type 2 diabetes. And people with type 2 diabetes often struggle to manage their weight. That is because insulin resistance, a hallmark of type 2 diabetes, can cause weight gain. It makes the body burn less fat and store extra sugar as fat. Many diabetes drugs, such as metformin and GLP-1 drugs, help with weight as well as lowering blood sugar. They can improve insulin sensitivity. They promote weight loss by cutting appetite, making you feel full, and helping burn fat.
Incretin drugs copy hormones the gut makes when you eat. Incretins raise insulin and lower glucagon. They also slow how fast the stomach empties. That can improve blood sugar and lead to weight loss. Several incretin drugs are approved for weight loss, including liraglutide (Saxenda), semaglutide (Wegovy), and exenatide (Byetta). Trials show these drugs significantly cut body weight and improve body chemistry.
Of these, liraglutide and semaglutide are used most for weight loss or obesity. Of the two, semaglutide (also called Ozempic or Wegovy) is stronger. So Ozempic, or semaglutide, is now the top choice of these drugs, and it is widely used for weight loss. But things are changing fast, and new incretin drugs keep coming. In 2022, the US FDA approved tirzepatide (Mounjaro) for diabetes. It is a once-a-week shot. New studies show this drug is unique in many ways and stronger than others in its class. More and more studies also show that it works very well for weight loss.
Is Mounjaro better than Ozempic and other diabetes drugs for weight loss?
Mounjaro may soon be approved for weight loss. The evidence suggests it is the most effective drug for weight loss. It works better than metformin, and even better than liraglutide and semaglutide (Ozempic or Wegovy).
There is a reason Mounjaro works better than Ozempic. The gut makes two main hormones of this kind: Gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). All the early incretin drugs, like liraglutide, semaglutide (Ozempic or Wegovy), and exenatide, only copy GLP-1. But Mounjaro belongs to a new class, because it copies both GLP-1 and GIP. So it has some added benefits. For example, GIP helps the body store fat and helps build bone, thus having greater metabolic health benefits.
Luckily, there is a head-to-head clinical trial of Ozempic and Mounjaro. Results from studies like STEP 2 and SURPASS-2 show that Ozempic (already approved for weight loss) and Mounjaro are fairly close. But Mounjaro is slightly better for weight loss. A 2.4 mg dose of semaglutide (Ozempic or Wegovy) could bring 9-10% weight loss in 40 weeks. Mounjaro brought 11% weight loss in 40 weeks at its top allowed dose (15 mg weekly). So, as you can see, Mounjaro is definitely superior, though the difference is marginal.
But keep in mind that while Mounjaro works better than other diabetes drugs for weight loss, it also often causes stomach and bowel symptoms. Studies show many patients have to stop Mounjaro because of more severe stomach problems. So it is fair to say Mounjaro is one of the most effective weight loss drugs in its class, but not always the safest. Ozempic may be slightly weaker than Mounjaro, but it is safer. And the stomach side effects of Ozempic are worse only in the first few weeks. After that, the body adjusts, and a person handles the drug much better.
In short, these are exciting times, as better weight loss drugs come out each year. So there is now hope that in the coming years, most people will be able to manage obesity with pills.
Frequently asked questions
What diabetic drug is best for weight loss?
Mounjaro (tirzepatide) is the most effective weight-loss drug studied so far. It beats metformin, liraglutide and semaglutide (Ozempic or Wegovy). In head-to-head results, 2.4 mg semaglutide brought about 9-10% weight loss in 40 weeks. Mounjaro at its top dose of 15 mg weekly brought 11%. The edge is real but small. And Mounjaro causes more stomach trouble.
How do diabetes drugs cause weight loss?
They work on the same problem that drives weight gain in type 2 diabetes: insulin resistance. It makes the body store extra sugar as fat and burn less of it. These drugs improve insulin sensitivity and copy gut hormones called incretins. That slows how fast the stomach empties, cuts appetite and makes you feel full sooner. So you eat less.
What is the difference between Mounjaro and Ozempic?
Ozempic (semaglutide) copies one gut hormone, GLP-1. Mounjaro (tirzepatide) copies two, GLP-1 and GIP. That puts it in a new class of drug. GIP adds its own effects, including on fat storage and bone building. Mounjaro is a once-weekly shot. Mounjaro brings slightly more weight loss. Ozempic is safer.
Is Mounjaro safer than Ozempic?
No. Mounjaro is the stronger drug, but it often causes stomach and bowel symptoms. Many patients have to stop it because those problems become severe. Ozempic is slightly less effective but safer. Its stomach side effects are worst in the first few weeks. After that, the body adjusts and most people handle it much better.
Does metformin help with weight loss?
Yes, to a degree. Metformin improves insulin sensitivity. That helps with weight as well as lowering blood sugar. For weight loss itself, though, the clinical evidence puts Mounjaro ahead of metformin, and ahead of liraglutide and semaglutide too. Metformin helps. It is not the strongest option in this group.
Some patients carry weight that adds to joint load and inflammatory pain. For them, these drugs are used within a physician-supervised medical weight loss program, not prescribed on their own.
Dr. Gurpreet Singh Padda, MD, MBA, MHP
