A longevity researcher is facing backlash for claiming to ‘reverse aging.’ Scientists say there’s no consensus on what it means.

He’s also earned his share of critics who say his research isn’t always backed up by sufficient evidence. But over the past months, The Wall Street Journal reported that Sinclair has been battling a new level of backlash from colleagues and researchers who say his claims on curing aging have gone too far.

A matter of semantics?

The controversy began on February 29, when Sinclair’s dog-supplement company, Animal Biosciences, issued a press release.

“I am very proud of the teams at NCSU and Animal Biosciences, who, after years of collaborative research and a clinical trial, have developed the first supplement proven to reverse aging in dogs,” Sinclair said in the release, according to Newsweek.

Sinclair contends that he was misquoted. “The actual quote that I had approved was ‘proven to reverse the effects of aging in dogs,'” he told the Journal, adding, “I felt this was a reasonable statement.” 

Scientists rushed to contest the claim. “The data is not good, you’re calling it the wrong thing, and then you’re selling it,” Dr. Nir Barzilai told the Journal. “The selling is a step too far.” Dozens of scientists resigned from The Academy for Health and Lifespan Research — a nonprofit organization of longevity researchers that Sinclair cofounded and headed as president. 

Dr. Matt Kaeberlein — a biologist who was among the throng of resignees — described Sinclair on X as the definition of a “snake oil salesman.” 

Sinclair resigned from the Academy in March, the Journal reported based on an email circulated by the Academy. Barzilai has since taken over as president.

Dr. Sinclair did not respond to a request for comment from Business Insider.

Animal Biosciences reissued a press release walking back the “reverse aging” claim. But scientists in the field say the issue is even more fundamental: There’s no way to reverse aging, much less measure it.

The concept of biological age — the true age that our cells, tissues, and organ systems appear to be, based on biochemistry, according to the National Institute on Aging — is gaining traction in longevity circles. Yet, it’s still a fuzzy and controversial concept because there’s no standard for normal aging. The way we age varies a lot from person to person. 

Experts working to standardize longevity medicine say it could take years before it’ll be recognized as an official field like cardiology or neurology, according to the MIT Technology Review. “This is a new field,” Andrea Maier of the National University of Singapore and cofounder of the private “high-end” Chi Longevity clinic told MIT Technology Review. “We have to organize ourselves; we have to set standards.”

Still, billions of dollars are being funneled into research. Longevity startups drew a global investment of more than $5.2 billion in 2022, according to PitchBook. And those backed by the world’s wealthiest executives like Jeff Bezos and Peter Thiel are dedicated to studying cellular aging — and its cures. That means debates about the semantics of aging will only become more relevant to our daily lives.