How does Zepbound work for weight loss?

If you’re contemplating taking Zepbound® for weight loss, you might wonder: Exactly how does it work? 

You’ve come to the right place. We’ve got answers about this new and novel GLP-1/GIP weight-loss drug and how Zepbound works for people with obesity or excess weight.

What is Zepbound? 

Approved by the U.S. Food and Drug Administration (FDA) in November 2023 and introduced in the U.S. shortly after, Zepbound (tirzepatide) is the first dual-agonist GLP-1/GIP drug for chronic weight management.

Made by Eli Lilly, this prescription drug is taken as a once-weekly injection just under the skin on the thigh, stomach, or the back of the arm. It’s FDA-approved for people with obesity and those with excess weight who have at least one weight-related health condition.

The active ingredient in Zepbound (for weight loss), and its sister medication Mounjaro® (for type 2 diabetes) is tirzepatide.

How does Zepbound work for weight loss?

Tirzepatide, the active ingredient in Zepbound, works by simulating GLP-1 and GIP, two of the body’s natural gut hormones that help regulate blood sugar, stomach-emptying, and appetite.

The hormone GLP-1 (short for glucagon-like peptide-1) does several key things after you eat:

• It tells the pancreas to produce insulin, which helps the body’s cells quickly absorb and use the sugars in the food you eat and avoid blood sugar spikes. 
• It inhibits the release of glucagon—a hormone that tells the liver to release stored sugar and raise blood sugar levels—which also helps moderate blood sugar.
• It slows stomach-emptying, which can make you feel full longer.
• It may also help signal to your brain that your stomach is full. 

GIP (short for glucose-dependent insulinotropic polypeptide) helps regulate blood sugar levels in response to the specific nutrients in food—such as carbohydrates and fats—by stimulating insulin and glucagon secretion. 

Both work to curb appetite and reduce overall food intake. Because of how Zepbound impacts metabolism and eating behavior, it becomes easier to stick to healthy habits. 

While some weight-loss medications, like Wegovy® (semaglutide) and Saxenda® (liraglutide), are GLP-1 receptor agonists, Zepbound (tirzepatide) simulates both the GLP-1 and GIP receptor cells. It binds to and activates—or agonizes—the receptors in the gut that register the body’s natural GIP and GLP-1 hormones.

How long does it take for Zepbound to work? 

According to FDA pharmacology reviews, tirzepatide reaches peak levels in the blood 8 to 72 hours after injection. So, while you may not immediately see a shift on the scale, it’s possible you might notice changes in your appetite within three days of taking your first dose of Zepbound. 

Whether and how quickly you’ll see weight-loss results depends partly on your unique physiology, diet, and exercise levels and how much of the drug your body can tolerate. 

The standard weekly dosage of Zepbound starts at 2.5 mg for the first four weeks, typically increasing to 5 mg for the next four weeks (depending on how well it is tolerated). Your health care provider may adjust your dosage in 2.5 mg increments up to a weekly maintenance dose of up to 15 mg (the maximum dose). Prescriptions are up to a medical provider’s discretion, and you should always follow your health care provider’s specific instructions for medications. 

How much weight can I lose on Zepbound? 

In one clinical trial, people with obesity (a body mass index, or BMI, of 30 or more) or excess weight (a BMI of 27 or greater) and a weight-related health condition who took a maximum weekly dose of Zepbound (10 mg to 15 mg) along with a reduced-calorie diet and increased physical activity saw an average weight loss of 20.9% after 36 weeks. 

Patients who continued taking tirzepatide maintained that loss (and lost an additional 5.5% of their body weight) over the next 52 weeks; the placebo group regained, on average, 14% of their weight.

Everybody—and each body—is different, so your results may vary. Even in clinical trials, some people did not lose weight with Zepbound. And Zepbound isn’t safe or effective for everyone. Research on Zepbound’s effects in people with additional or overlapping health conditions or those taking other medications is limited. 

What are the side effects of using Zepbound for weight loss?

In clinical trials, the most common side effects of Zepbound were mild. These included nausea, diarrhea, vomiting, constipation, stomach pain, indigestion, injection site reactions, feeling tired, allergic reactions, burping, hair loss, and heartburn.

But more serious side effects can occur with Zepbound, including severe stomach, kidney, or gallbladder problems; pancreatitis; low blood sugar (hypoglycemia); diabetic retinopathy or other changes in vision in patients with type 2 diabetes; and depression or thoughts of suicide. Zepbound hasn’t been studied in patients with a history of pancreatitis or those with severe gastrointestinal disease.

Tell your health care provider if you have severe stomach problems that won’t go away, including abdominal bloating or pain, acid reflux, a feeling of fullness after eating just a few bites of food, nausea, and vomiting, including vomiting undigested food eaten a few hours earlier. These may be symptoms of gastroparesis (stomach paralysis).

While it’s unknown if Zepbound causes thyroid cancer in humans, in studies it has caused thyroid C-cell tumors in rats. So, people with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2 should not take Zepbound. Do not use Zepbound if you have ever had thyroid cancer.

Zepbound may also cause fetal harm. If you are pregnant, breastfeeding, or planning to become pregnant, do not take Zepbound. Mounjaro, Wegovy, and Saxenda have many of the same potential side effects and risks. Find detailed side effect and risk information for Zepbound and other specific medications by name on our dedicated medication page.

About Found

Found is among the largest medically-supported telehealth weight care clinics in the country, having served more than 250,000 members to date. To start your journey with Found, take our quiz.

While tirzepatide is effective for weight loss, it is not clinically appropriate for everyone. Eligibility for these drugs is based on a provider’s evaluation of your medical history, MetabolicPrint, and lab work. If tirzepatide is not appropriate for you, our providers will work with you to determine an effective medication for your health profile. This content does not provide medical advice and does not substitute for a consultation with a doctor or healthcare provider.