Tanya Zuckerbrot & The F-Factor Diet Controversy, Explained

If you're interested in the wellness world (or, just influencer drama in general), you may have heard about the current controversy surrounding F-Factor, a weight-loss plan focusing on a fiber-rich diet, that comes with a line of protein bars and powders, and was created by a woman named Tanya Zuckerbrot. Now, consumers are alleging that they've experienced severe side effects from F-Factor products, including migraines, bloating, headaches, and even heavy metal poisoning.

The situation has been garnering increased attention as Emily Gellis, a fashion and lifestyle influencer, began posting hundreds of anonymous users' claims on her Instagram stories. They're detailing their experiences with the diet regimen, the products, and the culture surrounding the F-Factor diet — and some of it is pretty shocking.

There's a lot to unpack here, so let's get started.

F-Factor is a high-protein, high-fiber diet that is intended to be used as a weight-loss regimen. According to its website, "The F-Factor approach focuses on combining lean proteins with high-fiber carbohydrates, which are low in calories and keep you feeling full throughout the day." Zuckerbrot, a registered dietician, claims that, while on the F-Factor diet, typical feelings of hunger and deprivation that are usually associated with weight loss are eliminated. That's because, according to F-Factor, "the more fiber a food has, the more full you will feel after eating, leading you to consume less throughout the day. In addition, fiber has zero calories — so you get to fill up without filling out."

The website claims that following their fiber-rich diet could not only result in weight loss and management, but that it will also banish bloat, give you clearer skin, and can improve energy, sleep, and even your sex life.

But, it's also been described as too restrictive, according to one former follower. Via Twitter message, @PastaCats21 tells Refinery29 that she tried out the F-Factor diet for around six months this year, finally stopping in July. "The diet is under 1000 calories," she says. "They say they don't count [calories], but it's built in. You can't eat more than that." She also said she purchased a few of the F-Factor products, but didn't consume them after she was turned off by the Prop 65 warning labels on them (more about that later).

F-Factor started manufacturing their own protein bars and protein powders in 2018. Before their product line came out, they'd often recommend adherents try working GG crackers into their diet.

Tanya Zuckerbrot, MS, RD, is the founder of the F-Factor Diet and the author of two books, The F-Factor Diet: Discover the Secret to Permanent Weight Loss published in 2006 and The Miracle Carb Diet: Make Calories and Fat Disappear – with Fiber! published in 2021. According to her bio on the F-Factor website, she's also a lecturer, consultant, spokesperson, and national media personality.

The bio also says that she works with a limited amount of clients including celebrities, business and government leaders, and media personalities. According to a 2013 article published in the New York Times, Zuckerbrot's dietician sessions cost $600 for half an hour, and she also sells a $10,000 package that includes 10 visits with her. Her services also include a one-hour supermarket tour for $1,500, and a one-hour $1,500 refrigerator and pantry makeover.

The controversy started picking up when Emily Gellis, a fashion and lifestyle influencer on Instagram, spoke up about F-Factor's budding issues. She tells Refinery29 that she was first drawn to the accusations against the company and products by two now-deleted Instagram accounts, specifically one that allegedly detailed an experience between Zuckerbrot and her former private client.

"That's the comment that stood out to me that kind of got this story on my mind," Gellis says. "I ended up speaking about it, and it wasn't a big thing at the time back in April." But, by July, two more anonymous accounts popped up on Instagram (they no longer exist). One, Gellis says, was called "Page Six Has Eyes" and the other was called "Bitsy Whispers." Both of them started posting anonymous tips from women who claimed to have been negatively affected by the F-Factor diet and the protein powder, specifically.

Gellis shared the posts to her story to draw attention to the controversy, and it started to gain traction. Then, Gellis said, Zuckerbrot took to Instagram to post an IGTV video detailing her experiences with "cyber bullying" due to these posts. From there, Gellis says she had it. So she took to her own personal page, saying, "To turn a conversation about people who have been harmed by your products and turn it into a conversation about cyber bullying is a low I didn't expect to see the F-Factor team go," in an Instagram highlight titled "Open Discussion."

And that's where things heated up. DMs began flooding Gellis's inbox, all detailing people's experiences with F-Factor and their products. Gellis has now been posting them (anonymously) to her stories for the past two weeks, hoping to spread the word and, she says, show the people with these experiences that they're not alone.

According to the posts on Gellis's Instagram, former F-Factor users say the alleged side effects of consuming the products include things like migraines, nausea, vomiting, urinary tract infections, rashes, painful bloating, and even heavy metal poisoning. Customers have been questioning whether or not F-Factor's products contain high levels of lead, too.

Refinery29 was able to get in contact with an actual F-Factor consumer, who wished to remain anonymous. She tells Refinery29 that she ended up in the hospital due to her consumption of the brand's products.

She started following F-Factor in July 2019 and ordered two boxes of the peanut butter protein bars in August. "I went into the doctor because of headaches and abdominal pain, and I've never gotten headaches ever," she said. "Then I was hospitalized on September 19 because of abdominal pain. I never go to the hospital — only when I'm giving birth or if I break a bone — so it was bizarre."

She started consuming F-Factor's protein bars in August, and only stopped after being hospitalized. After her hospitalization, she threw out her remaining bars and never touched them again — and hasn't had any of the symptoms since. "At the root of this, the reason I'm upset is I was breastfeeding my baby while I was eating those bars. And who knows what I exposed her to," she said.

Her experience hasn't been directly reported to F-Factor. When asked why, she said, "I was near the end of the two boxes, so I just threw the couple of bars away that I had left and vowed to never use their products again."

"I wanted it to work," she continued. "It works for everyone else. It's so glamorous, like these are beautiful, rich, skinny, wealthy women that run around doing this diet. I just wanted it to work."

She was also bothered by the fact that F-Factor would not release their Certificate of Analysis (CoA), a document provided to consumers from a company that includes "specifications on characteristics such as purity, strength, composition and appropriate limits for ingredients in which there is a known or reasonable expectation that a contaminant or adulterant may be present." After initially citing a company policy to not disclose the document, the company has since released the CoA. F-Factor posted about the decision to do so on its official Instagram page on August 27. You can find the CoA on F-Factor's website, and on the Instagram page.

It's impossible to say that right now. There's no concrete evidence available that F-Factor's products are actually causing these severe symptoms — only anecdotal.

However, there is a warning label on F-Factor's products — a Prop 65 warning, according to their website — and it indicates that there is lead in the products. The Proposition 65 law was passed in California in 1986, and "requires businesses to provide warnings to Californians about significant exposures to chemicals that cause cancer, birth defects or other reproductive harm," the California Office of Environmental Health Hazard Assessment says.

"We do believe our products comply with Prop 65 (the lowest lead standard in the world)," F-Factor's website reads. "But to avoid potential lawsuits that many companies face, we feel like it is our duty and obligation to inform our customers."

"What I can categorically confirm is that the rumors of dangerous levels of lead in the product is false," Zuckerbrot told Page Six. "In over two years we have received less than 50 complaints asking for refunds. This rumor that somehow I created a product that’s harming people’s health is so malicious and frankly unfounded."

The official F-Factor Instagram page posted an initial statement on August 16, saying: "When it comes to testing our products, we test every batch to ensure they meet industry and FDA standards and that they are 100% safe for consumption." They went on to say that all soil naturally contains heavy metals, meaning that anything grown in the soil would also — aka their products.

In regard to the anonymous claims that F-Factor products have been harmful, they say they take every complaint seriously. "Specific to rashes and gastric distress, the cause tends to be either an allergic reaction to whey or an intolerance to high doses of fiber," their statement reads. "Among medical professionals, it is well established that an allergic reaction to whey protein can manifest in the form of rashes and/or hives. Furthermore, when fiber is introduced quickly into the diet and in large amounts, symptoms can include gas, bloating and gastric distress." If someone is experiencing these symptoms, F-Factor advises them to stop using the products.

In a statement provided to Refinery29 on August 25, Zuckerbrot said: "We are proud of our company and of the hundreds of thousands of our customers and clients who have used the F-Factor diet and products safely for good health and nutritious diet. The F-Factor Diet book was first published over 14 years ago, and it has been endorsed by countless nutritionists and physicians. Out of 174,000 distinct orders in the last 2+ years, we have had only 50 health-related complaints, less than .03% of total orders, and we will always work with our customers to identify and resolve any issue they’re having to ensure they can use our product safely. We have facts and science to support our results."

As of Refinery29's conversation with Gellis on August 19, F-Factor hadn't responded to her officially — but she has allegedly received multiple DMs on Instagram from Zuckerbrot's husband and employees of the brand. Refinery29 hasn't seen these DMs, but Zuckerbrot's husband, Anthony Westreich, commented on one of Gellis's posts saying, "I sent you a DM earlier can you please read and respond."