Exclusive | How Tanya Zuckerbrot lost her $40M diet empire to one troll, and the six year fight for justice

Aside from her allegations about Zuckerbrot’s products, Gellis accused the mom-of-five of using drugs, failing to pay taxes and engaging in criminal activity — all of which was untrue.

She told her Instagram followers, who now number 185,000, that Zuckerbrot was a “powder-pushing, money-hungry, disgusting, gaslighting, greedy woman”, who ran a “cult-like” operation.

Zuckerbrot said Gellis ultimately posted more than 50,000 videos about her and F-Factor.

“You can’t imagine what it feels like to be hunted,” she said. “I couldn’t leave the house. I would have panic attacks in the supermarket. I thought the world was believing what was being written about me.”

The registered dietitian said she lost millions in business and ultimately spent more than $1 million on lawyers fighting back.

But the toll went far beyond money, as Zuckerbrot admitted the campaign left her suicidal. “I lived with a cyber stalker,” she said.

It all started in 2020, at the beginning of the pandemic, when Gellis — who dubbed herself an “accidental activist” — began publicizing anonymous testimonials from followers claiming they had suffered serious physical and mental-health problems while following the F-Factor diet.

She had never met Zuckerbrot. But in just 75 days, Gellis posted more than 4,500 Instagram stories and posts about Zuckerbrot and F-Factor, according to court papers.

Gellis linked the products to everything from gastric distress and hair loss to panic attacks, UTIs, miscarriages and even death.

She also alleged F-Factor’s fiber powders contained dangerous levels of arsenic and contacted the company’s retail partner Bloomingdale’s to warn that it was selling “poison.”

Zuckerbrot, who has a master’s degree in nutrition and food studies from NYU, launched her F-Factor 20/20 fiber and protein powders and bars in 2018.

According to court papers seen by the Post, the products were manufactured in a pharmaceutical-grade facility and tested for microbiological safety, heavy metals and the accuracy of their label claims.

Within two years, Zuckerbrot said, the company was generating more than $1 million a month and had been valued at more than $40 million.

As the controversy exploded in August 2020, Zuckerbrot went on the “Today” show and released a certificate of analysis for F-Factor’s chocolate fiber/protein powder.

NBC News had the document independently reviewed by two nutrition consultants, who said the trace amounts of metals, including arsenic and lead, were at safe levels.

“Anything grown in the soil, even organically … can contain trace amounts of metals,” Zuckerbrot said at the time.

“It does not mean that they are not safe for consumption. In fact, we have the highest standards of testing to ensure our products are 100% safe for consumption.”

She added: “I do regret that we did not share this information sooner.”

But the online onslaught continued.

“At first, we’ were ignoring her,” Zuckerbrot told The Post. “We knew our products are safe.”

Gellis went on to claim that more than 10,000 people had contacted her with complaints about F-Factor.

That number would become one of the most significant issues in their eventual legal battle.

Zuckerbrot revealed that evidence obtained during discovery showed that Gellis had fewer than 100 complaints.

And Gellis, a married mom-of-two, has now acknowledged that her claims about the sheer number of purported victims were inaccurate.

Thousands of social-media posts about F-Factor were not thousands of individual complaints. And reports of symptoms did not, without medical evidence, establish that F-Factor products had caused them.

But by the time the true scale of the complaints emerged in discovery, the damage had already been done.

The allegations had become a national story, and the New York Times ran a major piece featuring Gellis posing for a glossy photo shoot, headlined, “The Great Diet Crash: A Crusade Against Tanya Zuckerbrot’s F-Factor Diet.”

And what had begun as claims about diet products became increasingly personal.

Gellis compared Zuckerbrot to perverts Jeffrey Epstein and Harvey Weinstein as well as members of the Sackler family (who owned Purdue pharma, which played a large role in the opioid crisis) and called her a “danger to society.”

She made allegations about drugs, taxes and criminal behavior, and even claimed that Zuckerbrot was sending people to stalk, harass, and intimidate her.

Now, six years later, Gellis has admitted that she got it badly wrong.

“What began as an inquiry evolved into a sustained and harmful campaign that was not grounded in verified facts,” Gellis said in a public apology filed in New York Supreme Court as part of the settlement of Zuckerbrot’s lawsuit.

Of some of the personal allegations she made about Zuckerbrot, Gellis was even more direct.

“None of these statements were true,” she said.

She also acknowledged that she went after the relationships underpinning Zuckerbrot’s business, contacting brand partners, celebrity clients and ambassadors and urging them to distance themselves from F-Factor.

“I did not rely on medical, scientific, or qualified expert analysis,” Gellis said. “I relied heavily on unverified and anonymous information from social media, which I presented as fact.”

“I contacted Bloomingdale’s, her retail partner, and told them they were selling ‘poison,’” she said. “I reached out to brand partners, celebrity clients, and ambassadors — pressuring them to denounce her, drop her, and distance themselves from F-Factor.”

“She told people I worked with, ‘If you don’t denounce her, I’m coming for you next.’ No one felt safe defending me,” Zuckerbrot said.

Gellis admitted that she blocked Zuckerbrot, her employees and others who attempted to respond — cutting herself off from information that could have challenged what she was posting.

“Instead of pausing to reassess, I continued,” she said.

For Zuckerbrot, those admissions explain why she insists this was never simply a six-year quest to wring an apology from Gellis.

She sued, she said, to stop the alleged defamation, cyberstalking and harassment — and to protect her name, family and business.

The apology came with the settlement. “My actions created a hostile online environment that contributed to humiliation and isolation,” Gellis said.

“I cannot undo the damage that was done. But I can take responsibility for my actions, and I do so here, fully and publicly.”

“To Tanya Zuckerbrot, I am deeply sorry. Yes, I want to say that again. I am deeply sorry.”

Zuckerbrot’s attorney told the Post, “In accordance with the Court’s Order entered on September 22, 2026 Ms. Gellis’s comment remains that the litigation between Ms. Zuckerbrot and her has been settled.”

With the settlement Zuckerbrot “wanted the amount to reflect the emotional harm she caused. The $240,000 represents the medical bills for the trauma treatment that helped save my life.

“I explained to the judge that her actions drove me — a mother of five — to the point of almost taking my own life. Without the help of my trauma doctors, I do not believe I would be alive today.”

And there is particular symbolism for Zuckerbrot in how the settlement will be paid.

“The $500 she will pay each month for the next 40 years will serve as a monthly reminder of the pain and suffering she caused and the treatment I needed to survive it.”

Zuckerbrot, who is married to corporate real estate investor Anthony Westreich, is now preparing to relaunch F-Factor in 2027 — and has no intention of rebranding.

“Absolutely not,” she said. “I’m proud of F-Factor and the thousands of people who have lived healthier lives because of it. I’m excited to bring our products back to market and back to the F-Factor community.”