Peptide Injections: the Latest Gym Trend for Muscle-Building and Fat Loss

People who want to feel younger, look fitter, or perhaps slough off a little layer of belly fat have been turning to an increasingly popular kind of treatment — one you can get without a prescription.

They’ve got obscure names like BPC-157, tesamorelin, and cerebrolysin. All it takes is a tiny needle and a little clear vial filled with injectable molecules.

Welcome to the world of peptides.

“Absolutely everybody’s asking for it, the field is popping,” Dr. Florence Comite, a longevity doctor who serves concierge medicine clients in New York City, told Business Insider.

The peptide landscape is so large that it almost defies definition. The prescription drugs Ozempic and Mounjaro, often used for weight loss, are peptides. So is insulin. There are peptides in skin creams, hair products, and high-end serums marketed to women to reduce fine lines and stimulate collagen. The wildly popular fitness supplement creatine? Also a peptide.

Then, there are the gym bro shots, said to boost muscle, burn fat, stimulate testosterone, and aid recovery.

Demand for peptide injections — something that biohackers and longevity-seekers have already been quietly using in the shadows for decades — is booming. Patients in pockets of the country saturated with peptides, like Beverly Hills, San Diego, Silicon Valley, and Manhattan are increasingly asking their doctors: “should I try peptides?”

Many physicians aren’t sure what to say because there isn’t a ton of great evidence around about how much peptides can really do. Plus, the FDA has been cracking down on peptide compounders in recent years. They worry that the hype is outpacing good evidence.

How peptides boost your body

Unlike most pills that doctors prescribe, peptides live in a more slippery area, between drug and bodily substance.

A peptide is a chain of organic compounds — specifically, amino acids — that stimulate natural processes. Depending on which amino acids a peptide is made of, and how it is used, the molecule can have all kinds of impacts on how our hormones operate. Peptides can improve fertility in both men and women, tamp down inflammation, remove dangerous visceral belly fat, or help build muscle. Others are thought to help improve sleep quality, even possibly improve brain health.

“What’s great about peptides is that they mimic the body,” said Comite, who has been working with peptides since she was a research fellow at the National Institutes of Health over 30 years ago.

Since most peptides are too fragile to be formulated as pills, they are often packaged as a clear liquid in a little vial. Users learn to inject their peptides using a very fine, short needle, right at home.

The popularity of peptides has soared on their reputation as ostensibly “natural” products. The idea being that, unlike other drugs or steroids, peptides are a safer choice because they’re just stimulating your body to do its own thing.

Taking growth hormones, for example, comes with a suite of undesirable potential side effects, like an increased risk of cancer and type 2 diabetes. What if you could just take a peptide that would stimulate your own growth hormone to make you stronger, leaner, and more energetic?

“The theory is that even if you use a growth hormone stimulating peptide, your body’s only going to be able to make so much growth hormone,” Dr. Sajad Zalzala, a longevity physician and one of the cofounders of AgelessRx, said. “Kind of like a check valve already in place. Again, that’s the theory.”

The peptides gym bros take to get chiseled muscles

One darling peptide of gym bros and longevity fiends alike is a substance called BPC-157. It’s known as the “Wolverine” shot for its perceived ability to heal you up and regenerate your body real fast like the Marvel character, Logan, after a big fight.

B-P-C stands for “body protection compound.” BPC-157 was first derived from stomach juices. It’s being investigated to treat inflammatory bowel diseases, including Crohn’s and ulcerative colitis. But the reason that athletes like it is because it’s thought to reduce inflammation and improve blood flow — and perhaps do even more.

There are a few other super popular peptides:

Tesamorelin, an injectable peptide, is prescribed to HIV patients to reduce excess belly fat. Sermorelin is supposed to help with sleep and recovery. CJC-1295 binds to growth hormone receptors in the body, and people often take it alongside impamorelin, which stimulates the hypothalamus. The two in tandem are said to deliver better muscle gains.

On Reddit and YouTube people share how they “stack” different peptides like this, taking multiple different kinds with the goal of boosting the effects of each.

One snag: The FDA is making peptides harder to access

Peptide fans get their shots at clinics and med spas — or, for less money, online.

Increasingly, people are ordering peptides that are labeled “for research only,” meaning they are supposed to be used by lab workers for experimentation, and were never meant to be put into human bodies.

That’s partly because the FDA crackdown on peptides has intensified in recent years, just as pharmaceutical compounding (a sort of acceptable way to get knock off medications) has surged in popularity, with people seeking cheaper versions of GLP-1 drugs like Ozempic and Mounjaro. At the beginning of 2022, the FDA had a list of four peptides that they said “may present significant safety risks” and should not be compounded. By the end of 2023, there were 26.

Comite thinks the FDA crackdown is a shame. She is finding it harder and harder to source compounded liquid BPC-157. She often uses a patch form of BPC-157 on herself, placing it over sore areas or injuries. Recently, she tore a calf muscle, so she’s been using it there, but she also just likes how taking a little bit of it keeps her active and moving.

“I use it almost every day,” she said. “It’s amazing for joints and everything — at a very tiny dose.”

Zalzala, who doesn’t usually prescribe peptides, ordered some topical BPC-157 recently when his wife had a knee injury. “My wife says it works,” he said, though he cautioned that it’s hard to really know if that’s true without more proper research.

Bracken Darrell, the CEO of VF Corporation and one of Comite’s patients, is also a BPC-157 convert. A self-proclaimed “basketball nut,” he’s on the court about three days a week. On the days when he doesn’t pick up a ball, he’s out cross-training on a bike or lifting weights.

So when he tore his meniscus about four months ago, he was worried. Under Comite’s supervision, he started taking liquid BPC-157 about three to four times a week.

He told BI it was “weird” at first, learning to inject the needle into an area of skin near his knee. But, pretty soon, it was just part of his routine.

“I believe it helped a lot, but it’s hard to know for sure,” he said. “There are people with a severely torn meniscus who don’t ever play basketball again, and I’m back — I certainly wouldn’t conclude that’s because I’m taking BPC-157, but at a minimum it didn’t hurt. And it sure seems like it helps.”

Proceed with caution, doctors say

Even longevity doctors who prescribe and use peptides regularly agree that some folks are overdoing it, and that could be dangerous.

“Proceed with caution, because you have to know the source and you have to know it’s active,” Comite said. “It’s not like Lowe’s or Home Depot where you can get stuff and you can fix the plumbing.”

In reality, the evidence for peptides is still murky. There are no big, randomized clinical trials like what we have for prescription drugs or vaccines. The current hype is based on anecdotal evidence, a few small human studies from decades ago, and rodent studies.

“People wanna take the peptides because they’re not from big pharma, they’re not mainstream medicine, they gotta be better than those cockamamie doctors,” Dr. Eric Topol, a cardiologist and longevity expert, said recently on the Dax Shepard podcast. “Where’s the data?”

For people who are using peptides, experts shared two pieces of advice:

Comite urges patients to start slow. A common mistake people who are dosing themselves make is thinking that “if a little bit is good, then a lot must be better,” she said. That’s not the case.

“Taking mega doses of tesmorelin along with testosterone causes your organs to overgrow,” Comite said. Sometimes she’ll see a toned gymgoer with a potbelly, and wonder whether that’s due to an enlarged liver or spleen.

Darrell recommends testing your peptides with an independent lab so you know what you’re getting is both real and uncontaminated.

Zalzala says his company started thinking about offering peptides a few years back, due to consumer demand, but they haven’t yet. There are just so many peptides out there, and it’s hard to tell which might be the very best.

Some of the most research-backed ways to have an impact on your longevity and fitness are still the simplest anyway: eat decent amounts of fiber and protein regularly, work out — at least a couple sessions with weights each week, and cut back (or ideally, eliminate) liquid sugar in your diet like juice and soda.