Newer weight-loss drugs: does stronger mean better?

A new weight-loss drug makes the headlines. People in a trial have lost even more weight than with the medicines we already know. It is easy to read that as a simple upgrade: like Ozempic, but stronger. And stronger must mean better.

That assumption is what we wanted to look at more closely.

The inspiration for this article was a video by Prof. Patrick Treacy, discussing semaglutide, tirzepatide and retatrutide, a newer medicine still being tested. Alongside weight loss, he raised questions about muscle, nutrition, heart rate and medical supervision.

His discussion prompted us to explore what “better” should mean for someone considering treatment. We looked at the research to understand what newer medicines offer and why losing more weight is only one part of the decision.

First, these medicines are different

People sometimes use “Ozempic” as a catch-all name, but it is one brand of one medicine.

These medicines act on signals the body uses to manage appetite, blood sugar and energy. Adding another target changes how a drug works; it does not automatically make it the best option for everyone.

The brand names matter too. In the EU, Ozempic is authorised for type 2 diabetes, while Wegovy is authorised for weight management in eligible patients. They contain the same active ingredient but have different approved uses and doses.

How much more weight can people lose?

In the SURMOUNT-5 trial, published in 2025, adults with obesity without diabetes lost an average of about 20% of their starting weight with tirzepatide, compared with 14% with semaglutide, over roughly a year and a half.

Retatrutide has also produced striking results. In the TRIUMPH-1 trial, published in September 2026, average weight loss in the highest-dose group reached about a quarter of starting body weight.

These are averages, not promises. Retatrutide was studied separately, so its result cannot tell us exactly how it compares with tirzepatide in the same patients. Both trials were funded by Eli Lilly.

Greater weight loss can be valuable. But those headline figures do not tell us how someone will feel during treatment, whether side effects will interfere with eating, or which medicine best fits their health needs.

Does weight loss mean losing muscle?

When people lose a lot of weight, some of it can come from muscle and other non-fat tissue.

In a study of tirzepatide, most of the weight lost was fat. A smaller share came from what researchers call lean mass. This includes muscle, but also water, organs and other tissue. A drop in lean mass on a scan does not mean that all of it was lost muscle.

The practical question is whether someone is staying strong and able to do their normal activities as their weight changes. New weakness is worth discussing with their healthcare team.

Eating less still needs to mean eating enough

When hunger becomes quieter, getting enough nourishment can take more planning.

Smaller meals may provide too little protein or too few essential nutrients. Nausea or vomiting can make eating and drinking harder. This does not mean everyone taking these medicines develops a deficiency; much depends on their diet, symptoms and health before treatment.

Guidance from medical and nutrition organisations recommends paying attention to food quality, protein and hydration. Supplements can help when needed. Not everyone needs the same collection of pills.

Manageable meals containing foods such as eggs, fish, beans, tofu or yoghurt can help with protein intake. If eating has become difficult, a dietitian can help adapt the plan.

Protein and strength training belong together

Protein supplies material the body uses to maintain muscle. Strength training gives muscles a reason to stay strong.

European guidance published in 2026 recommends both during treatment. Strength training means exercises that challenge the muscles, with the difficulty increased as appropriate for the person.

Protein shakes may help some people meet their needs, but protein alone is unlikely to preserve muscle as effectively without strength training. The amount needed should be personalised, particularly when other health conditions affect dietary advice.

Treacy also mentions creatine. It is being discussed as a possible addition, but research specific to these medicines is still limited. A September 2026 paper noted that no randomised trial had directly tested it during weight loss with GLP-1 medicines. We cannot yet say it prevents muscle loss during treatment.

What about the heart?

Treacy highlights changes in heart rate, particularly with retatrutide. An early trial did record increases in heart rate, especially at higher doses. These peaked during treatment and declined afterwards.

That needs context. A faster pulse alone does not tell us whether a medicine raises or lowers someone's overall risk of heart attack or stroke.

For semaglutide, the large SELECT trial found fewer heart attacks, strokes or deaths from cardiovascular causes overall in people who already had cardiovascular disease and had overweight or obesity, without diabetes.

That is reassuring evidence for the patients studied. Retatrutide needs its own long-term evidence; we cannot assume that one medicine's results apply to another.

A more effective drug can still cause side effects

Treacy describes finding Mounjaro easier to tolerate personally. Other patients may have a different experience.

In the direct comparison of tirzepatide and semaglutide, digestive problems were the most common side effects with both medicines, generally occurring during dose increases.

Retatrutide also causes digestive symptoms. In the TRIUMPH-2 trial in adults with obesity and type 2 diabetes, nausea and diarrhoea were more common than with placebo. Low blood pressure and unusual skin sensations were also reported more often.

How someone feels on treatment matters as well as how much weight they lose.

Retatrutide is still being studied

As of 27 October 2026, retatrutide has not been approved by a medicines regulator. Results from large trials are an important step, but they are not the same as approval.

Products sold online as “research peptides” should not be confused with the medicine supplied in a clinical trial. The FDA, the US medicines regulator, warns that unapproved products may contain incorrect ingredients, uncertain amounts of drug or harmful substances.

What should follow-up include?

Alongside weight, follow-up should consider what someone is eating, whether side effects interfere with meals, and how their strength and everyday activities are changing. Blood tests for nutrient deficiencies or scans to assess fat and muscle may be useful for some patients, depending on their needs.

“Stronger” can mean more weight loss. Whether a treatment is better for someone also depends on its side effects, their nutrition and strength, and the health benefits that matter to them.

A useful appointment question is: What makes this treatment a good fit for me, and how will we check that it is helping?