Is Mounjaro a Weight-Loss Wonder Drug?

Tirzepatide (Mounjaro) is the latest weight loss drug. Created to treat type 2 diabetes, it lowers your blood sugar and helps you lose pounds better than its rivals.

The diabetes drug tirzepatide (Mounjaro) is a hot commodity these days. A first in its class, the once-weekly injectable improves blood sugar control and is somewhat better than rivals at reducing your weight.

But you’re only in luck if you have type 2 diabetes. And it’s costly. You might pay $1,000 a month, sometimes as much as $1,500. Generally, insurers have price structures for tirzepatide to manage only blood sugar, leaving patients with obesity and normal blood sugar levels frustrated.  

If you do have high blood sugar, however, you might qualify for insurance coverage and maybe lose a big chunk of weight.

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How does Mounjaro work?

Mounjaro is a type of medication known as a dual incretin medication. Incretins are substances in your body that stimulate beta cells of your pancreas to release insulin — the hormone that lowers blood sugar after a meal and gives your cells energy.  

Type 1 diabetes is an autoimmune disease that occurs when your pancreas produces no, or very little, insulin. In type 2 diabetes, your pancreas produces insulin, but your body doesn’t use it effectively. You end up with too much sugar in your blood. People develop type 2 diabetes, or aggravate a genetic tendency, when they eat too many carbohydrates, especially white foods that quickly turn into sugar: white flour, sugar, potatoes, and rice.

When your blood sugar levels remain elevated too often, you may need oral medications, including insulin.

Your liver, muscle, and fat cells have two receptors that help your body produce insulin:

• Glucagon-like peptide 1 (GLP-1)
• Glucose-dependent insulinotropic polypeptide (GIP)

Mounjaro binds to both receptors to promote better insulin production. Other diabetes drugs on the market, like liraglutide (Victoza), semaglutide (Ozempic), and dulaglutide (Trulicity), activate only the GLP-1 receptor.

How does weight fit in?

Up to 90 percent of people with type 2 diabetes are overweight or obese. They typically eat too many carbohydrates, and their bodies store the extra sugar as fat. Taking insulin, however, can lead to more weight gain, unless you manage your calories and exercise carefully.

Drugs that work on the GLP-1 receptor make your stomach empty more slowly, which may make you feel more satisfied on less food. They also send signals to your body that tend to reduce appetite and cravings, making you eat less.

Because Mounjaro also binds to the GIP receptor, its effect on appetite seems to be stronger, leading to slightly more weight loss. In a study comparing Mounjaro to Ozempic, for example, patients lost 17 lbs. on average, compared to 13 on Ozempic.

Drugs that act on GLP-1 are approved to help control blood sugar for adults with type 2 diabetes. Ozempic is also approved to lower the risk of a heart attack or stroke in people with type 2 diabetes.

Ozempic is also approved for weight loss in a different dose under the brand name Wegovy. So is the GLP-1 drug Victoza, marketed for weight loss as Saxenda.

Mounjaro is not approved for weight loss alone, although your doctor may be willing to prescribe it to you for that purpose.

How effective is Mounjaro as a weight-loss drug?

The evidence on weight loss for Mounjaro comes from the SURMOUNT-1 study, a phase-3 clinical trial supported by the drug's manufacturer, Eli Lilly and Company.

The SURMOUNT study included more than 2,500 adults with:

• A body mass index (BMI) of 30 or more (considered obese)
• A BMI of 27 or more (considered overweight), plus at least one weight-related complication, such as high blood pressure, high cholesterol, heart disease.

Researchers randomly assigned the participants to one of four groups and gave them weekly injections of:

• 5 milligrams (5 mg) of Mounjaro
• 10 mg of Mounjaro
• 15 mg of Mounjaro
• An inactive placebo

Participants also received counseling sessions on healthy diet and exercise.

After a year and a half (72 weeks) on the medication, people in the 15-mg group lost, on average, nearly 21 percent of their body weight. Those in the 20-mg group lost almost 20 percent of their body weight. That's compared to a 3 percent weight loss with placebo.

A weight loss of 5 percent or more in people who are overweight or obese is linked to improvements in metabolic health including blood sugar and insulin levels. With other weight-loss medications, patients lost on average 3 to 8.6 percent of their body weight and saw improvements in their blood sugar.

Is Mounjaro safe?

Nausea is a common side effect. Up to 18 percent of people experience it, and about 17 percent have diarrhea.

Of the 6 percent of patients studied who had severe side effects, about a fifth of them may had symptoms related to COVID-19 infection rather than to the drug. Fewer than 1 percent of people in the study developed a type of gallbladder inflammation called cholecystitis.

How effective is Ozempic for weight loss?

In a study of 1,961 adults with a BMI of 30 or greater (or 27 if they had a weight-related condition, excluding diabetes), patients lost 15 percent of their body weight in 68 weeks, compared to 2.4 percent with placebo. The length of the study was about a month shorter than the Mounjaro research. Side effects and safety are similar to Mounjaro’s.

What you can do

If you’re eager to start losing weight, talk to your doctor about whether Mounjaro or another of the newer weight-loss medications could help you. Keep in mind their expense and insurance coverage issues if you don’t have diabetes.

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