This article was originally published with the headline “The Backlash Against the F-Factor Diet Shows How Restrictive Dieting Can Do More Harm Than Good”; it was updated on September 2, 2020, after receiving additional comment from the F-Factor team.

It all started in March, when fashion blogger Emily Gellis Lande stumbled across an Instagram thread where one user called out dietitian Tanya Zuckerbrot, RD, claiming her popular eating plan, the F-Factor Diet—which has been covered by top-tier media publications (including Well+Good), spawned two best-selling books, and inspired leagues of faithful followers—made her sick.

Things escalated in mid-June, when anonymous Instagram accounts began cropping up with allegations that the low-carb, high-fiber diet (and accompanying proprietary protein powders and nutrition bars) had left people with side effects like amenorrhea, gastrointestinal issues, hives, and eating disorders.

“[The accounts] all started telling stories about F-Factor, and about women who were in serious pain from this diet,” Gellis tells Well+Good. “Somebody sent them to me, and I reposted one of their stories—just to see what people would say. I ended up getting messaged by former employees and a bunch of people.” Since then, Gellis says she’s received about a thousand messages a day—many of them anonymous—all about F-Factor.

In an emailed statement to Well+Good, Zuckerbrot (who is the founder and CEO of F-Factor) defends the company’s reputation, practices, and products. “I have dedicated my entire career to helping countless people improve their health and safely manage their weight with F-Factor,” she writes. “At F-Factor, we remain dedicated to this mission as we work hard to make sure facts are shared, so all F-Factor clients, customers and followers can feel confident and proud in their decision to eat the F-Factor way. I am proud to stand behind the F-Factor Diet, our products, and our team, and will continue to respond to misinformation with facts and science.” In public statements on Instagram and in comments to the New York Times and New York Post, she has categorically denied all claims.

The F-Factor brand has a large following, particularly in New York City where Zuckerbrot lives: F-Factor’s official Instagram page has 109,000 followers; Zuckerbrot’s personal account has 117,000 followers; the brand’s official Facebook group boasts 8,000 members, and about 39,000 people have posted using the diet’s official hashtag (#ffactorapproved) on Instagram. Accordingly, the allegations against Zuckerbrot and her company have made national news, and caused a ripple effect throughout the nutrition industry. It’s clear people are paying attention to this controversy—but to what end?

The basic principles of the F-Factor Diet

According to the official F-Factor website, the eating plan is “a lifestyle that helps you lose weight and look great without losing everything you love.” The website’s home page proudly proclaims: “eat carbs, dine out, drink alcohol, and work out less.”

The diet’s defining feature is a focus on eating fiber—hence the “F” in F-Factor—with the explicit aim of helping people feel fuller while eating fewer calories. (The diet does not explicitly require followers to track or limit their calories. However, as the F-Factor website says, “The reason counting calories is unnecessary on F-Factor is that there is an inherent calorie-cap built into the program.”)

F-Factor asks followers to eat 35-plus grams of the nutrient per day (that’s 10 grams more than the U.S. Department of Agriculture’s 25-gram recommendation for women). Meanwhile, people are encouraged to eat standard amounts of protein, drink lots of water, and be mindful of their fats and carbohydrate intake.

In order to hit those fiber goals, F-Factor also highly recommends purchasing its F-Factor 20/20 Fiber/Protein Powder ($45; 20 grams of fiber, 20 grams of protein) and F-Factor Bars ($30 for a box of 12; 20 grams of fiber, 4 net carbs). There is also a book, The F-Factor Diet, that people are encouraged to purchase, an app where people can track their carbs and fiber intake, and the above-mentioned online communities where fellow F-Factor followers can connect.

People can also work directly with F-Factor dietitians with one-on-one nutrition counseling and group sessions. Some people have reportedly paid as much as $20,000 for these services, according to the New York Times.

The outcry against the diet

The F-Factor diet positions itself as a sustainable, empowering eating plan that allows people to live how they want (and drink alcohol to boot) while still meeting their weight and health goals. However, that is apparently not the experience of everyone who has tried the eating plan. The direct messages saved in Gellis’s Instagram highlights tell a story of alleged negative side effects of the F-Factor diet and products that vary greatly.

“Is there anyone else [who’s] gotten major canker sores and mouth sores?” asked one of Gellis’s followers about the diet. People also shared pictures of rashes, hives, and swollen tongues they attribute to the diet. One commenter anonymously wrote, “During quarantine, I ordered the powder and made so many recipes. I developed a horrible rash under my armpits and had a virtual dermatologist appointment. I was on three different steroids and nothing worked.” Claims of rectal bleeding, chest pains, and UTIs, are other recurring themes of the anonymous allegations that filled Gellis’s DMs.

Well+Good spoke to one woman, Katie* (her name has been changed to protect her privacy), who claims she started experiencing gastrointestinal issues after starting the F-Factor diet. The severity of the abdominal pain she was experiencing led her to seek medical care, but after two CT scans, her doctors were unable to determine the cause of her symptoms. While Katie remains convinced the diet was the issue (she says her symptoms cleared up once she stopped following the F-Factor protocol and using its products), this hasn’t been confirmed.

The symptoms that allegedly come along with the diet aren’t strictly physical. Hundreds of Gellis’s followers (again, some of whom are anonymous) have written in with stories about how the language and practices of the diet—such as meticulously counting carbs and fiber, wearing “intentions bracelets” to have a physical reminder of their diet goals, and marketing campaigns that implicitly connect being thin with beauty and success—have led them to develop a warped and even dangerous relationship with food.

In an Instagram comment directly appealing to Zuckerbrot, dietitian Brittany Modell, RD, wrote: “As an RD, I have personally met with clients who have struggled with their relationship with food after following the F-Factor Diet. Many of the meal plans were sub 1,000 kcal, which any practitioner would know is way too low for any female to consume. Several have lost their period or experienced their hair falling out.”

In a comment response, Zuckerbrot said that these are examples of people who follow the diet “to unhealthy extremes,” adding: “If you have an eating disorder, you should not follow any diet and you should seek professional help.”

In her statement to Well+Good, Zuckerbrot writes that her company “would never recommend a meal plan designed to help a person lose fat if that person’s initial evaluation showed that they might have or be at risk of developing an eating disorder, disordered eating, or an unhealthy relationship with food,” adding that they have referred such clients to clinical psychologists for treatment. “The F-Factor diet is aimed at good health, not just fat loss, which is why we help individuals actually gain weight nutritiously where needed. We recognize that everyone’s lives and goals differ, which is why F-Factor is not a one size fits all program. The program recommendations vary depending on a person’s sex, height, weight, age, activity, and more,” she adds.

How F-Factor has responded to the backlash

After weeks of people sharing their experiences with F-Factor—and flooding both the brand’s Instagram page as well as Zuckerbrot’s personal account with questions and allegations—the brand posted its first statement on August 17:

In the statement, the brand says that all of the F-Factor products are “100 percent safe for consumption,” tested for heavy metals, and FDA-approved. In response to the many people who’d asked the company to release its Certificate of Analysis (or CoA), a document that verifies a third-party has tested the quality of a product, Zuckerbrot initially said the diet company would not release it, citing that it contained “proprietary information.” However, in a follow-up statement released by the company on August 22, Zuckerbrot personally committed to releasing the CoA “within the next few days,” after the “growth of misinformation” about F-Factor and its products “generated anxiety” amongst the company’s clients.

“F-Factor has always been committed to transparency,” Zuckerbrot writes in her emailed statement. “While most dietary companies never release their Certificates of Analysis (CoA) because they contain proprietary information about the product itself, F-Factor has been discussing releasing our CoA for some time and we are preparing to do so with minimal information redacted. We do not have an official update as to when the CoA will be released, but it will be within days not weeks.”

As for the alleged side effects due to the diet, Zuckerbrot tells Well+Good: “We take complaints about our product extremely seriously. While some of our customers with whey sensitivities have experienced discomfort with our whey-based products, out of 174,000 orders in the last two-plus years, we have had approximately 50 health-related complaints which is less than .03 percent of total orders paced resulted in a formal complaint. We will always work with our customers to identify and resolve any issue they’re having to ensure they can use our products and program safely.”

However, Zuckerbrot doesn’t offer many specifics about the company’s protocol for investigating claims. “We take the time necessary to look into each complaint, and we will always work with our customers to identify and resolve any issue they’re having to ensure they can use our products and program safely. In addition, we work with an outside regulatory group to assess and respond to any complaint we receive,” she writes.

Katie never reached out to F-Factor. Until the allegations against the company surfaced a few weeks ago, she believed her reaction to the bars was entirely unique to her. A member of the F-Factor Facebook group, Katie says she’s watched people attempt to sell their F-Factor 20/20 Fiber/Protein Powders in light of the allegations and had their posts taken down. She’s seen the same happen in the group when people post about their side effects or troubles with the diet. Gellis also reports receiving threats against her life after publicly calling out F-Factor, as well as bullying directed at her own body and marriage. On Instagram, followers have also accused Zuckerbrot and the F-Factor official account of deleting critical comments.

Zuckerbrot tells Well+Good that the company follows Facebook and Instagram’s “community guidelines,” which she says recommend taking down “defamatory comments.” The company also deletes comments on social media that it considers to be “overly bullying and harmful in nature.” Additionally, she writes: “While I cannot speak to the actions of F-Factor clients or social media followers, I do not condone anyone engaging in cyberbullying of any kind.”

What the healthy eating world can learn from this

The alleged symptoms of the F-Factor Diet are so varied that it would be nearly impossible to trace each one back to a single root cause. Was it the powder and bars? The high fiber? Could it be the simple fact that, in following the diet, people changed their eating habits? So much remains unknown, but dietitians we spoke to say that when you boil down all of the comments, responses, outcries, and reported side effects, you’re left with one overwhelming truth: Restrictive dieting—and dieting culture at large—can be toxic.

“Restrictive dieting is a mindf**k,” says Brigitte Zeitlin, MPH, RD, a New York City-based nutritionist. “It lasts. It lingers for a long time, and any diet that is telling you, x, y, and z are off-limits should be a huge red flag to you. No healthy, long-term, sustainable lifestyle plan is going to tell you ‘this food is bad; that food is good.’ Food has no moral code.” While F-Factor claims to be flexible, the reality is that people are still asked to restrict their net carbohydrate intake, track their fiber intake, and eat less food than they would normally while on the diet.

Zuckerbrot denies the assertion that her diet plan is restrictive. “F-Factor is not a calorie counting diet, and we have never instructed or encouraged our customers to limit themselves to a certain calorie number,” she tells Well+Good. She reiterates that the diet is “aimed at good health, not just fat loss.” However, as Zeitlin outlines, limiting calories is not the only thing that defines a restrictive diet.

“Restrictive dieting is a mindf**k.” —Brigitte Zeitlin, MPH, RD

The F-Factor Diet is also an example of a diet that emphasizes something with objective nutritional benefits—fiber—to the extent that it ceases to be healthy. (Similar critiques could be applied to eating plans like keto, which focuses on fat intake, or Dukan, which does the same for protein.) “Fiber helps lower cholesterol, prevents diabetes, and can definitely help people achieve and maintain a healthy weight,” says Zeitlin. “A good amount of fiber is, honestly, 25, maybe even 30 grams a day. Anything over that can be excessive fiber.”  Too much fiber can lead to all types of GI distress, including bloating, constipation, or diarrhea.

Plus, consuming nutrients in highly-concentrated doses (like in protein powders) isn’t your body’s preferred way to function, says Zeitlin. “When you eat an apple, you’re getting fiber, but you’re also getting different vitamins and minerals that all work together in how your body breaks it down, processes it, and absorbs it,” she says. Per Zeitlin, fiber in powders and bars might not be bioavailable to your body, meaning your organs can’t properly absorb the nutrient because you’re eating it in isolation—which could increase the risk of adverse side effects.

The marketing surrounding F-Factor and virtually all other diets is also misleading, says Kelsey Miller, an editor, speaker, and author of Big Girl: How I Gave Up Dieting and Got a Life. “We’re living in a culture that tells us we don’t know how to eat,” she says. “The promise [of a restrictive diet] is that everything in your life will change and get better [once you follow the diet]—and of course it doesn’t. These diets are designed to be alluring and attractive; we walk around in a world that teaches us that the biggest project of our life should be controlling our bodies.”

Dismantling the idea that your body is a “project” and not a living, breathing organism is something that dietitian Alix Turoff, RD, (who once interned with F-Factor) has thought a lot about in her years since leaving the company.  The way that diets program us to think about food is deeply damaging and confusing, especially when they peddle contradictory philosophies, she says. “‘Just listen to your body,'” a standard refrain in the wellness world, “doesn’t feel helpful because you can’t listen to your body without your brain chiming in and saying, ‘Well, on F-Factor, it’s bad to have carbs’ or, ‘On Whole30, you can only have certain kinds of carbs’ and, ‘Dr. Gundy from Plant Paradox says that lectins are bad and simple carbs are inflammatory,'” Turoff says. “How can we expect women to make peace with their bodies when they’re constantly being fed conflicting information?”

Gellis, Miller, Turoff, and Zeitlin all hope that the F-Factor backlash will be a watershed moment for all diets. “I think the timing of this is interesting because, not only are we waking up to some of the insane pressures we have on us as women to look a certain way, but now, more than ever, there seems to be a demand for transparency on social media and people are sick of the glamorization of these unattainable lifestyles and beauty standards,” says Turoff.