Tirzepatide, sold as Zepbound, is currently the most effective weight loss drug available by prescription. In a 72-week head-to-head clinical trial against its closest competitor, semaglutide (Wegovy), tirzepatide produced 20.2% body weight loss compared to 13.7% for semaglutide. That translates to roughly 50 pounds lost for the average participant on tirzepatide. No other approved medication comes close to those numbers.
How the Top Two Drugs Compare
The SURMOUNT-5 trial, led by researchers at Weill Cornell Medicine, is the only large head-to-head study directly comparing tirzepatide and semaglutide at their maximum doses. After 72 weeks, tirzepatide users lost nearly 50% more weight than semaglutide users. The gap wasn’t just cosmetic: tirzepatide also reduced participants’ estimated 10-year cardiovascular disease risk by about 24%, compared to roughly 14% for semaglutide.
Both drugs are weekly injections, and both require a prescription. The key difference is in their biology. Semaglutide mimics one gut hormone (GLP-1) that signals fullness to your brain and slows digestion. Tirzepatide mimics two gut hormones (GLP-1 and GIP), which is why it’s sometimes called a “dual agonist.” That second hormone adds extra effects on insulin, fat metabolism, and appetite signaling in the brain, which appears to explain the larger weight loss.
Why These Drugs Work So Well
GLP-1 and GIP are hormones your body naturally releases after eating. They tell your brain you’re full, slow down how quickly food leaves your stomach, and help regulate blood sugar. The injectable drugs deliver much higher levels of these signals than your body produces on its own.
GLP-1 specifically activates neurons in the brain’s satiety center while also increasing signals through the nervous system that promote fat breakdown. It slows gastric emptying, which is why food feels like it sits in your stomach longer. GIP works alongside it by stimulating insulin release and directly influencing how your body stores and processes fat. Together, they reduce appetite from multiple angles simultaneously, making it genuinely easier to eat less without the constant hunger that undermines most diets.
What Oral Options Look Like
Not everyone wants or can access weekly injections. Oral weight loss medications exist, but they produce significantly less weight loss. The combination of phentermine and topiramate (sold as Qsymia) is among the more effective pills, reducing BMI by about 4.8% to 7.1% depending on dose in clinical trials. That’s roughly a third of what tirzepatide achieves.
An oral version of semaglutide is also available. Pricing through discount programs runs around $299 per month for the pill form, compared to about $349 for the injection through the same programs. The oral form can be more convenient, though the injectable version generally delivers more consistent absorption.
Side Effects to Expect
The most common side effects of GLP-1 drugs are gastrointestinal: nausea, vomiting, diarrhea, and constipation. These affect roughly 50% to 60% of people starting treatment. The symptoms are dose-dependent, which is why doctors start you on a low dose and gradually increase it over several weeks or months. For most people, the nausea fades as the body adjusts. It tends to be worst during dose increases.
Tirzepatide and semaglutide have similar side effect profiles. The gastrointestinal issues are a direct consequence of how these drugs work: slowing digestion and changing gut signaling inevitably affects how your stomach feels, especially early on. Eating smaller meals and avoiding high-fat foods can help manage symptoms during the adjustment period.
Weight Regain After Stopping
This is the part most people don’t hear about upfront. A systematic review published in The Lancet’s eClinicalMedicine found that within one year of stopping a GLP-1 drug, people regained about 60% of the weight they had lost. The data suggests regain eventually plateaus at around 75% of lost weight. In practical terms, if you lost 50 pounds on tirzepatide and then stopped, you could expect to regain 30 to 38 pounds over the following year or so.
This happens because these medications don’t permanently change your metabolism or appetite set point. They suppress hunger while you take them. Once the drug clears your system, the biological signals driving appetite return to their previous levels. For this reason, most obesity specialists treat these drugs as long-term, potentially lifelong medications, similar to blood pressure or cholesterol drugs.
What They Cost
Without insurance, Wegovy carries a list price of about $1,350 per month, or roughly $16,200 per year. Zepbound falls in a similar range. Discount programs can bring costs down significantly. GoodRx, for instance, offers introductory pricing around $199 per month for injectable semaglutide, with ongoing fills at $349 per month.
Insurance coverage varies widely. Many plans now cover these medications for people with a BMI of 30 or higher, or 27 with a weight-related condition like type 2 diabetes or high blood pressure. Some insurers still classify them as lifestyle drugs and deny coverage. If cost is a barrier, manufacturer savings programs and pharmacy discount cards are worth exploring, as they can cut the price by 70% or more in some cases.
What’s Coming Next
A triple-hormone drug called retatrutide is currently in Phase 3 clinical trials. Where tirzepatide targets two gut hormones, retatrutide targets three: GLP-1, GIP, and glucagon. Early-phase trials showed weight loss numbers exceeding what tirzepatide achieves, and the ongoing Phase 3 trial is tracking body weight changes over 80 weeks along with cardiovascular risk markers like blood pressure, cholesterol, and triglycerides. If approved, it could push the ceiling even higher, though final results and an approval timeline are still pending.
For now, tirzepatide (Zepbound) represents the most effective option backed by completed head-to-head data. Semaglutide (Wegovy) remains a strong second choice and has a longer track record. Oral medications work for milder weight loss goals but don’t deliver comparable results. Whichever option you’re considering, the weight regain data makes one thing clear: the drug works best as part of a long-term plan, not a short-term fix.