Do all peptides work? Evidence and side effects

This content is sourced exclusively from TruthTides clinical reference data and does not constitute medical advice.

Wait, you mean the internet lied to me?

It is easy to scroll through your feed and get the impression that every peptide is a guaranteed home run. We love a good success story, but the reality is that the term peptide covers a huge range of substances. Some have mountains of evidence, while others are still in the "we hope this works" phase.

Think of it like professional athletes. Some are legendary MVPs with decades of stats, and others are just rookies who had one good practice. You wouldn't treat them the same, and you shouldn't treat all peptides the same either.

The Heavy Hitters (The A+ Group)

There are a few peptides that have been through the ringer and come out with top marks. These are FDA-approved and backed by massive clinical trials (fancy talk for big studies with lots of people).

• Semaglutide: This one has a Grade A+. In the STEP 1 study, it showed 14.9% weight loss. It is FDA-approved for brands like Wegovy and Ozempic.
• Tirzepatide: Another Grade A+ superstar. It works on two different hormone receptors at once. In the SURMOUNT-1 study, it achieved 22.5% weight loss, which was actually superior to semaglutide in head-to-head tests.
• Tesamorelin: This Grade A peptide is approved to reduce visceral adipose tissue (that is the stubborn fat around your organs). In studies, it reduced this deep fat by 18%.

The "Almost There" Group

Not every peptide has reached the finish line. Some look great on paper, but the long-term data hasn't arrived yet. Scientists are still working on these — turns out the human body is complicated. Who knew?

• Retatrutide: This one holds a Grade B+. It hit 24.2% weight loss in Phase II trials, which is the highest seen so far. However, Phase III results are still pending, and it has a higher side effect rate than its cousins.
• Thymosin Alpha-1: This has a Grade A- and is approved in over 35 countries, but it is not FDA-approved in the US. While it helps with immune response, it has been disappointing when used alone for cancer treatment.
• MK-677: Technically not a peptide (it is a small-molecule ghrelin mimetic), this has a Grade B. It might increase muscle mass, but it can also raise your fasting glucose and worsen your insulin sensitivity.

The Fine Print (Because there is always a catch)

Even the best peptides have "evidence gaps." For example, both Semaglutide and Tirzepatide raise concerns about muscle mass loss. Plus, for Semaglutide, weight regain is substantial once you stop taking it.

Then there are the side effects. For Semaglutide, nausea is reported by 44% of people. There are also strong safety signals for things like vomiting and delayed stomach emptying. Basically, your body might not be as thrilled about the process as you are.

What should you do next?

You shouldn't just take a stranger's word for it when it comes to your biology. Look for the actual grade and regulatory status before you dive in.

This is a great one to bring up with your doctor. You can find peptide-experienced physicians in our Find a Doctor directory.