• A new study tracked the "biological age" of people who swapped some of their meat for more veggies.
• Eating more vegetables and complex carbohydrates seemed to improve basic health metrics.
• Importantly, people didn't lose strength when they cut back on animal protein, from 50% to 30%.

Pump up the veggies, beans, and nuts, and pare down the meat, just a little bit.

That appears to be the takeaway from a new study tracking how changes to the typical "Western" diet, subbing in more vegetables and lowering saturated fat content, might contribute to healthy aging.

The study, conducted in Australia, fed roughly 100 healthy adults aged 65 to 75 a rotating menu of freshly prepared, unprocessed meals for one month, only changing up how much fat, meat, and carbohydrates different people ate on different diets.

The study was short, but on both functional measurements like grip strength, as well as clinical tests and measures of an emerging health metric called "biological age," people appeared to derive a slight health benefit from replacing some of their daily meat with plant proteins, and replacing saturated fat with more complex carbohydrates.

"What we wanted to do was a study that actually provided some real information about the causal relationship between macronutrients and health in old age," senior study author Alistair Senior, a nutrition scientist at the Charles Perkins Centre at the University of Sydney, told Business Insider.

The results lend more evidence to the idea that cutting back on, but not necessarily eliminating, meat can be good for a person's long-term health.

"Even our vegetarian diets weren't 100% vegetarian," Senior said. "They aim for about 70% of the protein coming from plant sources, and 30% from animal sources."

Three diet tweaks made a typical 'Western' diet healthier

For the study, researchers split participants into four different groups. They were instructed to only eat the food given to them during weekly meal deliveries for a full month. No alcohol, no extra sweets, no ultra-processed snacks.

"It's not perfect, people cheat, people might not be reporting everything they eat, but I think we did as good as is feasible," Senior said.

There were two "omnivore" diets:

• Diet 1: 14% protein, ~40% fat, ~40% carbohydrates

A meal on this plan was the closest to a standard, "Western" diet, with half of the protein intake coming from animal products.

For example: chicken tikka masala with white rice and green beans.

• Diet 2: 14% protein, ~30% fat, ~50% carbohydrates.

Similar to the first diet, with half of the protein from animal sources. This diet includes more carbohydrates from whole grains and vegetables, and has a lower fat content, with ingredients like brown rice and quinoa included more often.

And there were two "pro-veg" diets:

• Diet 3: 14% protein (less meat), ~40% fat, ~40% carbohydrates

For example: yellow coconut curry with rice, veggies and tofu.

• Diet 4: 14% protein (less meat), ~30% fat, ~50% carbohydrates.

A meal on this plan includes more carbohydrates like potatoes.

For example, a veggie-heavy cottage pie, with peas and carrots on the side, was on the menu.

People on diets 2, 3, and 4 all ended the month with measurable improvements to their "biological age," as measured with the Klemera-Doubal Method, which includes data from regular blood tests a doctor might order at an annual exam, like blood pressure, cholesterol, and creatinine levels. People who ate diet No. 1, the high-fat pro-meat "Western" diet, saw no change on their "biological age" tests. All four diet groups lost about the same amount of weight, an average of roughly four pounds, three of those being fat (this may just be a result of the nature of the trial, as a no-junk-food, no alcohol plan).

The study, while still preliminary, suggests older adults don't have to load up on meat to maintain their muscles and strength as they age.

Why meat may be bad for longevity

When people reduce their meat and saturated fat intake, they change the forces that are acting on their cells.

Senior says the amino acids in animal proteins turn on pro-growth pathways that tell our cells to grow and reproduce. Too much cell growth in old age can be a bad thing, propelling disease processes like cancer. Longevity scientists are also studying how the opposite of cellular growth and proliferation, what's called autophagy, the process by which starving cells eat and recycle themselves, may be a longevity-booster.

Meat consumption also amps up oxidative stress on cells, and can increase chronic inflammation, which is linked to many age-related chronic diseases, like high blood pressure, Type 2 diabetes, and heart disease. In particular, animal proteins that are not "lean" and have a higher saturated fat content, like those in red and — most especially — processed meat, are known to be pro-inflammatory, whereas protein-rich foods like fish, beans, and eggs tend to be more anti-inflammatory.

Sneak fiber into your meals

Longevity researcher Dan Belsky, who studies biological aging, and who was not involved in the study, said it is a "reassuring" finding for nutrition science.

"On balance it seems like maybe a little less meat, a little more veg in your diet is a good thing," Belsky, an associate professor of epidemiology at Columbia University, said. This idea goes along with decades of other research, in studies that have tracked what people eat over months and years, and looked at their health outcomes. Even among identical twins, people who eat more plants and less meat seem to do better on standard health measurements.

"We know we can manage our risk for heart disease, diabetes, reduce our risk for many cancers," Belsky said.

Nutrition is personal. How individuals respond to different foods can vary a lot, based on our genetics, our gut microbiome, and lifestyle.

Still, decades of research suggest a diet high in red meat is not great for your health and longevity.

Senior says you can easily mix your meat with other protein sources, like beans.

If you're making a bolognese sauce, why not substitute half of the meat for lentils? Beans are famously rich in dietary fiber, which can improve blood sugar, lower cholesterol, and tamp down inflammation.

"We're not even saying you need to go for a fully vegetarian diet, but trying to substitute some of that [meat] out might do the trick," he said.

• Serena Williams is returning to tennis at age 44, with her first pro match the week of June 8.
• Williams has been open about using a GLP-1 to lose weight, saying it helps her move better.
• Her comeback is great news for people who believe in peptides for longevity and performance.

The GOAT is bounding out of retirement.

Tennis great Serena Williams is back in the game, after openly endorsing GLP-1s for weight loss, and emphasizing how great her knees feel at her new, lower weight.

"I'm moving better on Ro," she said in a Super Bowl ad for Ro, a telehealth company that prescribes Ozempic, Wegovy, and Zepbound. (Williams' husband, Reddit cofounder Alexis Ohanian, sits on the board and is a major investor.)

In the commercial, Williams said she can move more easily and enjoy steadier blood sugar levels throughout the day while she trains. In general, she feels "healthier" on her injectable medication, which she's said helped her lose 34 pounds after the birth of her second child in 2023.

"After having two kids, I wasn't able to be at a weight that was healthy for me," Williams told the "Today" show when she first announced her paid partnership with Ro in 2025.

Her comeback is huge for tennis, of course — but also for the burgeoning peptide movement.

Yes, GLP-1s ("glucagon-like peptide-1") are peptides.

For the uninitiated, injectable peptides are hot stuff right now. They have become wildly popular among gym-goers, athletes, and bodybuilders looking to trim fat, control inflammation, and avoid injuries. Ultimately, they want to find an edge in their routine.

Peptides are critical signaling molecules our bodies use to build muscle, heal injuries, and control hormones. Gym bros' favorite peptides include BPC-157 (aka "the Wolverine shot") for recovery, ipamorelin CJC-1295 for lean muscle growth — and, of course, GLP-1s for weight loss.

To be clear, Williams isn't suggesting that GLP-1s should be used as performance-enhancing drugs. She is simply emblematic of a growing trend, from regular folks on up to competitive bodybuilders and elite athletes, who are using GLP-1s to stay nimble as they get older.

Her experience mirrors what many doctors are seeing in clinical practice: Their patients are recognizing GLP-1s as a health optimization tool — seeing that the fat reduction and anti-inflammatory benefits of these drugs go beyond treating diabetes and obesity. Research shows the medications can improve heart health, liver function, and sleep quality. And scientists are also probing whether these drugs could help with healthier aging and longevity.

"It's the most powerful drug we've ever seen for helping people lose body fat," exercise physiologist Pat Davidson, who is using an unapproved GLP-1 drug to help shred fat for bodybuilding, told Business Insider. "You are never putting that genie back in the bottle."

GLP-1s target dangerous belly fat

The trend isn't limited to high-powered sports stars.

In San Francisco, Dr. Nima Afshar, a concierge doctor at longevity-focused Private Medical, said he has "dozens" of elite clients who are using these drugs to remove dangerous visceral fat from their midsections and feel better in their bodies.

Visceral fat is stored deep in the belly, providing essential cushioning for vital organs such as the liver and kidneys. While some visceral fat is normal, too much can be a problem, as this fat is metabolically active, and can impact a person's risk of developing chronic conditions like heart disease and diabetes.

Increasingly, Afshar is initiating conversations with patients who he says are "not that overweight" but who he thinks could use these drugs to boost their longevity by driving down visceral fat stores and lowering inflammation across the body.

"I almost don't use the word weight," Afshar said. "Some people can carry visceral fat, but tolerate it well and have no metabolic effects — that's uncommon." For most people, extra "toxic" mid-section fat, which is not always visible, "can ultimately make you not feel quite as good."

Once the negative signaling from that extra visceral fat is gone, a whole chain of health benefits can ensue, he said.

Afshar uses multiple clinical measurements — including InBody scans, routine bloodwork, liver and kidney ultrasounds, and blood pressure readings — to assess whether GLP-1s could be prescribed to improve a patient's health.

At the same time, he recommends all his patients on GLP-1s up their protein intake to "the maximum" recommended dose, and incorporate more movement into their daily routines, to help safeguard their musculature and prioritize fat loss over muscle wasting as they eat less food.

Some private insurers are getting wise to the same idea and mandating that patients adhere to some kind of exercise and nutrition program in order to get access to these medications.

Dr. Mitch Biermann, an obesity medicine physician at Scripps Health in San Diego, said the practice is emblematic of a wider shift in his field, toward a more holistic assessment of excess fat and body composition.

While insurance companies may not cover every indication (i.e., medical reason to take a drug), doctors are increasingly prescribing GLP-1s to a wider array of people with health concerns tied to carrying around excess weight, including joint pain, inflammation, and high blood pressure.

"I think there are quite a lot of indications that people can justifiably use the medicine," Biermann said. "There are just many different definitions of obesity now."

Bodybuilders and athletes are using peptides to get an edge

Whether it was steroids or insulin, bodybuilders have long used exogenous hormones to pursue bulgier muscles, along with protein-rich diets and more strength training than cardio.

GLP-1 drugs are essentially the next generation of that playbook: powerful new drugs that are like supercharged versions of our own hunger-checking hormones, which can help athletes get lean.

Take Davidson, the bodybuilder, who is gearing up for a couple of Mr. Universe-style bodybuilding competitions this July. He's aiming to cut his body fat, without sacrificing muscle.

So, alongside his ultra-high-protein, low-carb diet, he started taking an ultra-powerful but not-yet-released GLP-1 drug called retatrutide, which is still in development at Eli Lilly, about three months ago. (He's part of a groundswell of gym-goers tapping into underground "peptide" markets selling research materials.)

Davidson said he has lost over 30 pounds in three months. He feels like the GLP-1 has helped him maintain more strength than he usually does in the slim-down phase before a big event.

"I really haven't gotten any weaker," Davidson said.

Afshar said the "super optimizers" like Davidson are rarities in his practice, but he knows at least a few people who fit into the category.

Doctors vehemently recommend against doing this without medical supervision.

Williams is not part of this performance enhancement and fitness-optimization-through-peptides band of GLP-1 users; she is promoting these drugs for FDA-approved uses, including blood sugar control and clinical weight loss.

Still, her big comeback to the court next week is great news for the pro-peptide guys, who are keen to show that peptides are much more than drugs to treat chronic diseases like obesity and type 2 diabetes.

A man with a mysterious case of full-body hives in Abu Dhabi. A Californian rushed to the hospital with a life-threatening allergic reaction. A fit, gym-going man in Texas with soaring blood sugar — inexplicably headed for pre-diabetes.

Doctors working on the bleeding edge of longevity care in high-end clinics around the globe — from concierge practices in wealthy enclaves of California to premier longevity centers in the Middle East — say they're seeing an uptick in both interest in, and injuries from, injectable peptides.

A peptide is simply a short chain of amino acids, too short to be called a protein. We have thousands of them in our bodies. Some are hormones like insulin, some help our muscles grow, some aid in healing. Injectable peptides promise people a boost on top of what nature delivers, such as deeper tanning, better fat burning, greater muscle growth, and improved wound healing. Still, rigorous human studies on these claims are often lacking.

As more people attend peptide "parties" and inject unknown substances sourced from friends or online dealers, doctors are sharing horror stories about some of the worst-case DIY peptide scenarios they've seen.

Many say they are putting out "fires" and dealing with bizarre, unexplained health issues that, after some medical investigation, end up being tied to unauthorized, grey-market peptide use. Injuries they've seen range from simple to serious, including minor injection site reactions and major hormonal disturbances.

Recently, at Dr. Nicole Sirotin's Institute for Healthier Living longevity clinic in Abu Dhabi, practitioners linked a case of full-body hives to an at-home peptide injection.

"These kinds of immune reactions," Sirotin said, "people might not be associating with the peptides."

That makes it hard to gauge how widespread peptide injuries are — from simple injection issues, to contamination, or improper dosing. Anecdotally, however, doctors say there's been a huge uptick in peptide use over the past year, fueled by influencers touting their benefits on social media.

Business Insider spoke to seven doctors, including some who use peptides in their practice and some who don't recommend them. They're concerned about growing interest in and willingness to experiment with unauthorized peptides.

Hives, messed-up hormones, and insulin resistance issues

People are drawn to peptides because they promise targeted, almost "shortcut" fixes for weight loss, muscle gain, and antiaging — often with little oversight from doctors.

They act like messengers in the body, influencing or acting as hormones that control growth, metabolism, and other key functions. Because these substances mimic normal hormonal processes in our bodies, they've developed a reputation as safe and "natural," though there are very few rigorous human studies to support that claim.

The effects of "stacking" multiple peptides into a daily or weekly regimen, including ones for fat loss, muscle growth, tanning, better hair and skin, have also not been studied.

Originally, bodybuilders were drawn to peptides for muscle gains and the promised benefits to physique. Then, post-COVID, biohackers were attracted to this style of do-it-yourself medicine, and now doctors told Business Insider that antiaging enthusiasts and affluent patients can't get enough of this stuff.

In Texas, Dr. Farhan Abdullah, the medical director at Magnolia Functional Wellness in suburban Dallas, said that over the past year, he's seen an uptick in moms, housewives, and "white collar people who are kind of approaching middle age" taking an interest in peptides.

"You look at RFK, and you look at what's going on, and you would think it's just a bunch of gym bros that are interested in peptides, and it's really not," he said.

There are dozens of peptides to choose from, and doctors stress that each should be evaluated individually.

Abdullah's patients tell the board-certified physician that they're often skipping the pharmacy, and sourcing their peptides online, or getting them secondhand from friends, like an injectable drug version of a Tupperware party.

In his worst-case scenario to date, one patient, who he described as a young "fit" man, developed early insulin resistance from a growth hormone-stimulating peptide that had him charting a course toward early diabetes. Because growth hormone and insulin counterbalance each other, excess stimulation may lead to insulin resistance, a risk not well studied in peptide use.

"This guy with no family history, he was a fit dude, he was jacked, he was working in the gym, had early insulin resistance," Farhan said.

Dr. Meena Verma, who runs Blue Coast Longevity clinic in Newport Beach, California, said one of her patients had a severe, life-threatening allergic reaction to a peptide shot and landed in the hospital "that night."

"Obviously, we see it all over social media — Instagram influencers — everybody is pitching peptides," she said. "Where the patients are getting their peptides is a big concern."

Dr. Lisa Cassileth, a plastic surgeon in Beverly Hills, said the worst issues she has seen so far have been minor, such as injection-site redness from unsterile pokes or improper storage of peptides. Other issues with peptide injections can stem from contamination issues.

Not all doctors are entirely against peptides, especially when used in controlled settings. Cassileth prescribes some peptides to her patients when they are recovering from surgery, but wouldn't recommend injecting them all the time or obtaining them from online sellers.

"Peptides are just going to be another drug," Cassileth, founder and CEO of The Practice Healthcare, said. "We just have to learn how to use them correctly."

Cassileth uses the very popular "Wolverine" peptide BPC-157, a compound that will be up for debate at a July FDA meeting. It is often sold online "for research purposes only," meaning it's not human-grade.

Cassileth sources hers from state- and federally-regulated compounding pharmacies, licensed as "503A" and "503B," which are held to a higher standard. She said she often uses BPC-157 on her patients after surgery as it's marketed to promote faster wound healing and tissue repair, but said it's not something people should take every day. She called it a "one-week" peptide.

"There's no hormone or enzyme in your body that just hits you nonstop in high doses," she said.

While she believes that the anti-inflammatory and reparative benefits outweigh the risks for short-term use, she wouldn't put someone on it indefinitely. "Don't do excess because you don't know what it does yet," she said.

Cassileth is hopeful that the practice of using peptides will develop into a well-studied approach for various conditions and be marketed by major pharmaceutical companies.

"Pharmaceuticals — go for it," she said. "Please save us from this thing being in some kind of weird space where only functional medicine people prescribe it."

Could peptides solve aging? Maybe someday.

Other longevity-focused doctors take a more measured stance on peptides and said far more research is needed in humans before doctors start prescribing these substances.

Dr. Andrea Maier, a professor of medicine at the National University of Singapore who runs the Chi Longevity Clinic at the Four Seasons there, said that the clinical evidence simply isn't there yet for a lot of these peptides.

"At the moment, we are hearing that peptides could solve the aging trajectory — and I think it might be right," Maier said. "I think we should study it well, to give it in a very well-regulated way."

When she hears of "peptide parties" and "peptide festivals," she worries about the potential for harm, where something is being injected with only "a thought that this might help."

Her concerns aren't just theoretical. Regulators are increasingly scrutinizing the fast-growing peptide market. The FDA has restricted several peptides over safety concerns and warned companies against selling unapproved versions online. In September, the agency announced it was cracking down on imposter versions of the weight loss shots semaglutide, tirzepatide, and retatrutide being imported from abroad.

Canadian authorities recently warned that unauthorized peptides can lead to hormonal imbalances, mood swings, blood sugar issues, organ damage, and tumor growth.

GLP-1 is the darling peptide

There is one all-star peptide that experts across the board said they endorse, use, and would like to study further for its effects on aging and longevity: GLP-1, the hormone-mimicking peptide behind Ozempic and Mounjaro.

"I have like 80% of my patients ask me about GLP-1s and 5% about peptides," Dr. Nima Afshar, a physician at Private Medical San Francisco, told Business Insider. "Even people that are pretty healthy, boy, they're thinking about [GLP-1s] because my patients are rational and they understand this is evidence-based, and it does seem to have some longevity benefit."

He doesn't broadly recommend the entire class of compounds, though. When his patients ask, "Should I be on peptides?" or say, "I've heard peptides can help" for things like an energy boost, improved muscle mass, or better libido, he generally says "no." Though he's open to adjusting that stance in the future as more data comes in.

Dr. Evelyne Bischof, who runs a healthy longevity medicine practice in Shanghai and Tel Aviv, said she is not "radically against" peptide use, but her patients only use FDA-approved peptides like Ozempic, "and only from very reliable providers." She has concerns about unauthorized peptides causing allergic reactions, or including extra substances that aren't listed on the label, like steroids.

"I don't think any scientists would be anti-peptide," Sirotin, the longevity doctor in Abu Dhabi, said. "We're just anti-self-experimentation with random molecules that are research-grade."

"Partly, the reason I think it's so concerning is because these are presumably healthy people who want to be healthier," she said. "The problem is you might be entering a one-way door, and you damage your liver, or you damage your kidneys."