Weight Loss Drugs Compared: Tirzepatide Leads Semaglutide and Liraglutide

Weight loss drugs are now so widespread that it can seem as though they all work in much the same way.

People commonly call them by the brand name they know best, or use whichever option their insurance policy covers.

The belief is that each of these medicines delivers broadly similar outcomes. However, a new study indicates that this is not the case.

After comparing the three leading weight loss drugs, researchers identified substantial differences in the amount of weight people lost, with one medicine clearly outperforming the rest.

Same drugs, different results

All of these medicines are part of the GLP-1 family, named after glucagon-like peptide-1, a hormone released by the gut following a meal.

The drugs mimic this signal, lowering blood sugar and delaying stomach emptying so that hunger remains suppressed for longer.

This combination has made the medicines exceptionally popular. A recent survey found that around one in eight American adults currently uses one, while almost one in five has tried one.

Before this, the three approved drugs had not been compared directly among people without diabetes who wanted to lose weight.

Pooja Gokhale, a pharmacy doctoral student at the University of Georgia (UGA), served as the corresponding author of the review.

Tirzepatide is the leading weight loss drug

The researchers combined findings from 15 large randomised trials involving more than 14,000 participants. Most trials compare a single medicine with a dummy treatment rather than with another drug.

As there were no direct head-to-head data, the team connected the separate studies to produce an indirect ranking of the medicines.

Tirzepatide, marketed as Zepbound for weight loss and Mounjaro for diabetes, ranked first, with people losing more than 20 percent of their initial body weight.

Semaglutide, the active ingredient in Wegovy, followed at about 15 percent.

Liraglutide, sold as Saxenda, produced the lowest result at approximately 8 percent. The greatest reductions were seen with the highest tirzepatide doses, around 10 to 15 milligrams per week.

In this respect, the findings suggest that Tirzepatide could be the preferable option.

The added hormone effect

Tirzepatide differs because it has a second target. Wegovy and Saxenda work only on the GLP-1 system, whereas tirzepatide also activates another gut hormone that contributes to appetite and digestion control.

In a major obesity trial, participants taking the highest dose of tirzepatide lost almost a quarter of their body weight over roughly 16 months.

It acts on two signals rather than one. The researchers believe this dual action is what gives the medicine its advantage.

However, the review assessed outcomes rather than the biological processes behind them. It can show how much weight each drug reduced, but it cannot explain why the two-target method performs better; it only shows that people taking tirzepatide finished lighter.

Daily injections fall behind

As the oldest of the three medicines, liraglutide performed considerably less well than the others. It also places greater demands on patients, requiring an injection every day instead of the once-weekly schedule used for the two newer drugs.

A daily injection can be easier to miss, and missed doses generally lead to poorer outcomes.

Combined with the smallest weight reduction in the group, this regimen helps explain why liraglutide has lost ground to more powerful alternatives.

The researchers also looked for a medicine that could work without adding side effects such as nausea and stomach problems, which are common throughout this drug class.

On this measure, the older daily treatment was unable to match the others.

An alternative to injections

Because injections discourage many potential users, a version that can be swallowed has clear appeal.

The researchers carried out a separate scenario analysis to assess how an oral form of semaglutide could compare with injections.

At a 50-milligram dose, the tablet outperformed liraglutide and the lowest tirzepatide dose, although it did not equal the results from stronger tirzepatide doses.

Gokhale described it as nearly on par with injected semaglutide.

When the review was completed, regulators had not yet approved the oral version for weight loss.

A 25-milligram tablet has since entered the market, underlining how quickly this area continues to develop.

Stopping has consequences

There is an important limitation that any ranking can obscure. These weight loss drugs are effective only while they are being taken, and weight generally returns after injections are stopped, a pattern seen across the class.

“What some people don’t understand is that when they stop taking the medication, they may gain all that weight back,” said the study’s co-author, Lorenzo Villa-Zapata, an assistant professor of pharmacy at UGA.

One study reported that people regained roughly two-thirds of the weight they had lost within a year of stopping treatment.

The new analysis did not examine what occurs after people stop using the medicines, meaning its ranking applies only during treatment.

Choosing the right weight loss drug

For the first time, doctors and patients have a clear head-to-head answer for adults without diabetes who take these drugs for weight loss.

Tirzepatide takes off the most, semaglutide comes next, and liraglutide trails. A clear order, at last.

That ranking gives prescribers reason to consider the drug tirzepatide first when the goal is maximum weight loss with the fewest stomach complaints.

It also gives patients a clearer picture before starting a long, costly treatment.

The next challenge is answering the harder questions: how to prevent weight regain after treatment, and whether a less expensive pill can deliver the same results as the shots.