Will retatrutide help me lose weight or look ‘shredded’?

Injectable peptides are generating a lot of buzz online.

One of these is retatrutide, a drug that’s being described as the next big thing in weight loss. Some say it may be even more powerful than Ozempic or Wegovy, two other popular weight loss drugs. Beyond health care, gym-goers are using it to try to get leaner, faster. This trend is sometimes dubbed “leanmaxxing”.

But there’s a catch. Retatrutide is still experimental. It hasn’t been approved for use anywhere in the world, yet it’s already circulating through illicit online markets.

So is retatrutide a safe way to lose weight? Or does it bring more risks than rewards?

What is retatrutide?

Retatrutide, often shortened to “reta”, is a peptide that researchers are still testing in clinical trials. Peptides are short chains of amino acids that help your body heal wounds and reduce inflammation.

Retatrutide acts on three hormone pathways that affect your appetite, metabolism and blood sugar levels. The first is glucagon-like peptide-1, otherwise known as GLP-1. This hormone reduces appetite and slows down the rate at which food travels through your stomach. The second is GIP or glucose-dependent insulinotropic polypeptide, which helps regulate blood sugar and fat storage. Glucagon, which also helps manage your blood sugar levels, is the third.

By acting on these three hormones, retatrutide is designed to reduce both how much you eat and how much energy your body burns.

The results from early trials are striking. They suggest retatrutide may lead to even greater weight loss than current regulated therapeutic treatments. This includes an increasingly popular type of weight loss drug called semaglutide, widely known under brand names including Ozempic and Wegovy. In one 2023 trial, participants receiving higher doses lost more than 20% of their body weight over 48 weeks. But this trial was conducted in a tightly controlled clinical setting with medical supervision, carefully selected patients and regulated dosing. That’s very different from buying a product online and using it without guidance.

Read more: Injectable peptides are the new anti-ageing trend. But what evidence do we have they’re safe for humans?

Why are gym-goers interested?

For some, having a weekly retatrutide injection that suppresses appetite and increases fat loss is an attractive idea.

Losing a large amount of weight quickly can make people look leaner and, in some cases, more “defined” or “shredded”. This is especially appealing in aesthetics-focused cultures.

However, rapid weight loss doesn’t just mean losing fat. It often also reduces a person’s muscle mass, especially if they don’t eat enough protein or do enough resistance training. But many gym-goers want to build muscle, rather than lose it.

There’s also a psychological side to consider. Appetite suppression can make it easier to eat well, but it may also take away the joy of eating good food, especially in social settings. Recent research suggests retatrutide may affect a person’s mood, motivation and relationships. However, scientists don’t yet understand how or why.

Read more: 3 signs your diet is causing too much muscle loss – and what to do about it

Are there any risks?

Current research suggests retatrutide can cause several side effects. This is supported by anecdotal reports from social media. The most common side effects are gastrointestinal. These may include nausea, vomiting, diarrhoea and constipation.

These symptoms can be mild for some people, but severe for others. There has already been at least one reported case of a person dying, after they used the drug and developed severe diarrhoea. However, this case is still being investigated.

There’s also a lack of regulation controlling where, when and how people can access retatrutide. Enhancement drugs, including peptides such as retatrutide, sold online or through unofficial channels may be contaminated with other harmful materials. They may also have incorrect doses of retatrutide or contain none at all.

Earlier this week, Australia’s Therapeutic Goods Administration specifically warned about the dangers of importing and using unapproved peptide products, both for consumers and suppliers.

Read more: Ozempic isn’t approved for weight loss in Australia. So how are people accessing it?

Could it affect your mood or relationships?

Based on some recent media reports, it seems peptides such as retatrutide may affect more than just appetite.

These medications act on brain pathways involved in reward and motivation. This means they might affect your desire to consume food or alcohol. Other research indicates peptides such as retatrutide may affect a person’s sexual drive. Some people describe feeling “flat” or emotionally detached, while others report negative changes in their relationships.

The bottom line

Current research suggests retatrutide can lead to significant weight loss. However, that’s not the same as becoming “shredded”. That relies on other factors such as prioritising resistance training, eating a protein-rich diet and staying hydrated.