- The F-Factor diet has been around for years, based on the premise that filling up on fiber suppresses appetite and leads to weight loss.
- But the program and its founder, the dietitian Tanya Zuckerbrot, are now at the center of controversy. Followers have linked the plan and its products to health problems, including gastrointestinal distress, eating disorders, hives, hair loss, and menstruation loss.
- Insider spoke with four women who said they’d experienced such issues. Emily Gellis, an influencer who’s been anonymously sharing these reports, said she’d heard from roughly 2,000 people. They’re calling for more transparency from F-Factor.
- There’s no proof that F-Factor caused the health consequences, but nutrition experts say they could occur on any restrictive plan.
- Zuckerbrot denied claims that F-Factor caused eating disorders or other ailments and described the criticism as “slander” from people who are against diets.
- Visit Insider’s homepage for more stories.
In the summer of 2018, Sami Miller decided to go on a diet. After struggling through various food fads and trying to overcome what she called “bad eating habits,” the 24-year-old read “The F-Factor Diet” by Tanya Zuckerbrot, a 2006 book espousing a high-fiber diet that promised to hold the secret to “permanent weight loss.”
The book and the diet changed everything about her life, Miller told Insider in a phone call. She became obsessed with the high-fiber, low-carb, low-calorie eating plan.
But Miller said that while following the diet, she experienced a host of health problems, including severe digestive issues and amenorrhea, or the pausing of menstruation, which is often linked to anorexia. She told Insider that her doctor said that if she continued on the diet, she could become infertile, a complication of amenorrhea.
Within a year, she said, she’d developed an eating disorder that she believes stemmed from her strict adherence to F-Factor. She ended up at the Monte Nido Eating Disorder Treatment Center in New York City, where she recovered after six months of treatment.
“It literally led me to a big depression. I just was, like, isolating myself. I was afraid to go out. I was afraid to drink,” Miller said. “My whole year was just ruined.”
Miller is one of four women Insider spoke to who said they had negative experiences they believe are related to F-Factor, ranging from gastrointestinal issues like gas and bloating to eating disorders, amenorrhea, hair loss, and severe hives. Their stories are anecdotal and don’t prove causation.
About 2,000 people, mostly women, have anonymously aired similar complaints, according to Emily Gellis, 34, a fashion influencer who has been sharing their experiences on her Instagram account since the spring.
But F-Factor’s founder and CEO, Tanya Zuckerbrot, 48, a New York City registered dietitian, denied claims that her diet had caused physical and mental-health issues, telling Insider in an interview that the accusations were an example of anti-diet advocacy gone too far and a harassment campaign to ruin her career.
“The F-Factor diet followed as prescribed in the ‘F-Factor Diet’ book does not cause hair loss or loss of a menstrual cycle,” Zuckerbrot said.
In her two decades of business, she said, she’s had no health-related lawsuits filed against her, “just a lot of slander on social media.”
The high-fiber, low-carb diet became a flashpoint on social media when an influencer began posting anonymous complaints on her Instagram stories
The high-fiber, high-protein, low-carb diet is based on the premise that fiber fills you up and is calorie-free, so eating lots of it — 35 grams daily, significantly more than the 25 to 30 grams recommended by the American Heart Association — helps prevent hunger, leading to weight loss and other health benefits without having to count calories, restrict alcohol, or even exercise.
The F-Factor website includes recommendations like eating a specific brand of Swedish high-fiber crackers and following the “three bite rule,” to allow dieters to indulge in treats in a way that won’t “destroy your entire day of eating.”
In 2018, the diet company introduced its first line of retail products. F-Factor bars and powders pack 20 grams of fiber and protein per serving. That’s more fiber than two Fiber One bars and as much protein as a double-patty hamburger.
As for the diet recommended in the F-Factor book, which predates the products by more than a decade, readers are warned that they “may experience some initial bloating and abdominal cramps when they begin to eat large amounts of fiber,” especially if they were eating small amounts before. “It is important to introduce fiber slowly,” the book says.
Gellis, who has 173,000 followers on Instagram, has brought voices of former F-Factor dieters into the spotlight. The influencer said she began receiving direct messages from people claiming they’d experienced serious side effects from F-Factor or its products after she shared complaints she saw about the diet on social media.
Gellis, who has never followed the F-Factor plan herself, posted those anonymous complaints on her Instagram stories, leading more people to share their experiences with the diet and inspiring influencers in the health and wellness space, including some registered dietitians, to voice their concerns.
Zuckerbrot addressed the allegations on August 16, a few months after Gellis’ first posts about F-Factor. In a statement on Instagram, the company said its products were safe and addressed concerns about GI issues, acknowledging that “when fiber is introduced quickly into the diet and in large amounts, symptoms can include gas, bloating and gastric distress.”
On Monday, one hour after The Times published a story about the F-Factor controversy, the brand posted a quote from Zuckerbrot. “We have facts and science to support our results,” she said.
Many former followers of the F-Factor diet have asked the company to apologize to people who suspect their symptoms are related to the diet and to release a certificate of analysis, a quality-assurance report that includes the results of lab testing on its products, to validate that the products’ advertised nutritional information is accurate and that they don’t contain undisclosed ingredients.
As of Tuesday evening, the company had done neither.
Women say their symptoms include hives, digestive distress, and hair loss
Fernanda Rodriguez, a 25-year-old law student who splits her time between St. Louis, Missouri, and New York City, wanted to lose weight for her wedding. In January 2019, she began the F-Factor diet after hearing people in her circle praise it for its ease.
Rodriguez said that despite being open about her history of an eating disorder and gastrointestinal issues, an F-Factor employee encouraged her to get on the diet during a free new-client consultation the company was offering at the time.
The representative also told her that her past eating disorder was an asset because it showed discipline and that she should avoid cardio exercise because it would make her hungry, Rodriguez said.
(Zuckerbrot denied these claims and told Insider that an F-Factor employee would be “terminated” for these advisements.)
Rodriguez began the diet anyway, which, for her, typically included a half a scoop of F-Factor protein powder and two hard-boiled eggs for breakfast; spinach, chicken, and a cheese stick for lunch, and “pizza” crackers for dinner.
While Zuckerbrot contends that followers of F-Factor aren’t told to count calories and the book does not specify a caloric goal, Rodriguez said that when she followed all the recommended recipes, it added up to fewer than 1,000 a day.
Despite the advice to avoid cardio, Rodriguez continued to run because she knew it was important for her mental health, she said.
Unsurprisingly, she lost weight — 2 to 3 pounds a week — but she also experienced stomach pain and “ridiculous” hives, and she was “losing hair in clumps,” she said.
Like Miller, she also became obsessed with the plan.
“I would go to sleep thinking, ‘S—, I only had 32 grams [of fiber] today, let me just eat half a bar super fast before it’s midnight,'” Rodriguez told Insider. “Was I back to throwing up like I did all through high school? I wasn’t. Was I still having a complete disconnect, emotionally and physically, to what I was putting in my body? Yes.”
When the coronavirus pandemic brought her back to quarantine in New York City, where she didn’t have a robust stash of F-Factor products and her husband questioned her eating patterns, Rodriguez’s dedication to the plan faded.
Simultaneously, she said, her hair thickened, her hives dissipated, and her stomach pain eased.
But she said she didn’t put two and two together until her husband pointed it out and health personalities she followed on Instagram began sharing their experiences with the diet.
When she asked if anyone else experienced similar symptoms on the private F-Factor Facebook group, she was kicked out, she said.
She said she was speaking out to push for transparency in the products and acknowledgment of some people’s concerns about the plan.
Aside from the recent acknowledgment on Instagram and the book’s recommendation to add fiber slowly, F-Factor hasn’t issued warnings about adverse reactions and has deleted some negative Instagram comments
Some women who spoke with Insider — and who Gellis said reached out to her — said they assumed other issues were responsible for their distress because there are few negative reviews on F-Factor’s website or Instagram account.
Zuckerbrot told Insider that the company did delete some negative comments from its Instagram page. “We felt we were following community guidelines when it was slander,” Zuckerbrot said. “When people say, ‘Your products have lead and are poisoning people,’ or ‘I lost my period,’ and we know that there’s absolutely zero correlation between our product and those claims, why would you leave that there?”
As of Tuesday evening, there were several negative comments on F-Factor product pages. Reviewing the F-Factor peanut-butter protein bar, one person said they had “bad stomach aches,” while another said the bar tasted “artificial.”
Zuckerbrot added that out of the 176,000 unique orders from F-Factor since 2018, there had been only 50 complaints of adverse reactions to the products. Zuckerbrot said her team believes that those complaints, which all involved either stomach issues or rashes, were due to whey allergies.
Other women say they experienced severe bloating and dangerous swelling on the plan
Another woman Insider talked with said she experienced serious digestive distress while on the plan. “I couldn’t button my pants. I was extremely uncomfortable, and I didn’t know what was wrong with me,” she said. The woman told Insider that she didn’t want to link her name to the issue, citing the risk of lawsuits and cyberbullying.
She increased her fiber intake gradually and drank plenty of water — the only solutions F-Factor offered, she said — but her problems didn’t go away until she stopped using the products almost a year after beginning.
Another woman, Anne McCall, 60, who lives in the San Francisco area, said she experienced rashes and eye swelling when she started eating F-Factor products.
She said that while she tried changing her eye cream and stopped wearing jewelry and her watch, the reaction continued until she stopped her F-Factor smoothies and bars.
Others have told Insider and said via Gellis’ Instagram that they had high levels of lead in their blood after consuming F-Factor products, but Insider was not able to independently corroborate these claims with medical practitioners. (One of the fundamental components in a certificate of analysis is screening for the presence of heavy metals.) In a statement on Instagram and in an interview with Insider, Zuckerbrot denied those allegations.
But followers who say they’ve experienced reactions see a lack of transparency about what exactly is in F-Factor’s products.
“I think all anybody really wants to know is what is inside of that stuff that could be causing all these problems,” McCall said, “and we haven’t been able to get any answers.”
Zuckerbrot said the company should not be expected to release its proprietary product information. Still, she said F-Factor would soon release a certificate of analysis “as a result of misinformation and health accusations” and to validate the safety of the products.
A high-fiber diet — or any diet, really — could have health consequences, but F-Factor followers want transparency
There’s no proof that the F-Factor diet caused any of the symptoms followers have mentioned.
Nutrition experts not affiliated with the program said that the symptoms they described would be understandable on any extremely high-fiber, low-carb, low-calorie program.
Take the amount of fiber — 20 grams — in a single serving of an F-Factor product.
“You’re basically sitting down to a cup and a half of black beans in one sitting,” Keri Gans, a registered dietitian, told Insider. “Not to say this is going to affect everybody negatively, but it could.”
While the diet prescribes 35 grams of fiber a day, about 10 grams more than the US Department of Agriculture’s recommendation for women, devout followers are likely eating closer to 40 to 60 grams per day, Tamara Duker Freuman, a registered dietitian who works in a gastroenterology clinic that’s treated F-Factor followers, told Insider.
“And here’s the thing about fiber: All that goes in must come out,” Duker Freuman said.
Nutrition experts who spoke with Insider also said that claims about F-Factor triggering eating disorders made sense to them — any restrictive eating pattern can harm vulnerable people.
“Dieting leads to food and body preoccupation, overeating and binging, lower self-esteem, weight cycling, and disordered eating behaviors and eating disorders,” Alissa Rumsey, a registered dietitian, told Insider.
Undereating can lead to amenorrhea and, in the longer term, increase the risk of fertility issues and miscarriage. Nutrient deficiencies can contribute to hair loss.
As for complaints about rashes and swelling, they could be allergic reactions to ingredients in the F-Factor products, like the soluble corn fiber or nuts, Gans said.
Zuckerbrot denied claims that F-Factor has led to health problems and eating disorders, and she called the program a ‘lifestyle’
Zuckerbrot described her program as a “lifestyle” that had worked for her, her family, and thousands of others over the 20 years she’s been a registered dietitian.
She told Insider that she believes many of the claims about F-Factor were fabricated by people who are against diets and want to harm the empire she’s spent two decades building.
Zuckerbrot said that over the spring and summer, she had faced a harassment campaign on Instagram that largely stemmed from two anonymous accounts sharing stories of people who had negative experiences with F-Factor.
Zuckerbrot said those accounts were removed after her team sent them cease-and-desist letters. Soon after that, Gellis began posting about the controversy, Gellis and Zuckerbrot both said.
Zuckerbrot said she believes that the thousands of direct messages sent to Gellis about F-Factor were false.
“The one thing I know with certainty is F-Factor as a program is safe and sound,” she said, “and we also have thousands of clients that we have helped to lose weight.”
When asked whether she was aware of any people who had struggled with eating disorders as a result of F-Factor, Zuckerbrot said, “The nature of that inquiry just concerns me.” She said she had never been made aware of any such complaint.
Zuckerbrot said that if a person following F-Factor developed an eating disorder, the diet shouldn’t hold the blame. “I think any diet can lead someone who’s not doing it properly or working with professionals to get an eating disorder,” she said. Zuckerbrot compared this to an alcoholic blaming the liquor store for their addiction.
But, she said, “the last thing I want to do is blame the victims.”
When body-positivity culture meets diet culture
The backdrop of Gellis’ and Zuckerbrot’s feud is an industry in flux. Dietitians increasingly advocate body positivity and “health at every size” counseling, while programs like Zuckerbrot’s F-Factor are considered by many to be the old guard of diet culture.
Popular diet programs like Weight Watchers and Jenny Craig have shifted their branding in recent years to move away from a strictly pro-diet mindset. But F-Factor’s messaging has largely remained focused on weight loss.
Zuckerbrot said that while she wouldn’t encourage an underweight person to lose additional weight, the company would look to “improve as an organization” and “take a closer look” at messaging that could be considered harmful.
F-Factor has undoubtedly helped people to lose weight healthfully. But now the company’s success is predicated on a revival of the outmoded pro-diet mindset. That’s not a line of thinking that’s in vogue anymore, and Zuckerbrot knows it. “That’s what is sort of sad,” she said. “It’s this next generation of young dieticians who hate diets and have an anti-diet message.”
Most of the women who spoke to Insider said they had nothing against Zuckerbrot.
“I have no vendetta whatsoever,” McCall said.
Rodriguez said she felt bad for Zuckerbrot and F-Factor, “because I don’t think they intentionally wanted to hurt anyone.”
“But what I expected was more transparency behind the product creation and a sincere apology,” she said, “and it’s not happening.”