A science journal has retracted a study claiming that the “Gut Makeover” — a trendy four-week diet that recommends lots of vegetables and chewing — helps people lose weight and feel better.
The Gut Makeover program, which includes popular books and expensive Mediterranean retreats, was designed in 2015 by British registered nutritional therapist Jeannette Hyde. Her diet purports to “nourish your microbiome,” the trillions of microbes that live on or in the human body.
Last year, Hyde published a study in the journal PLOS One looking at how 21 people responded to the diet. The journal retracted the study Tuesday, citing “methodological concerns,” as first reported by Retraction Watch.
Hyde and her coauthor, psychologist Kate Lawrence of St. Mary’s University in London, stand by their work.
“This retraction is disappointing and somewhat bizarre,” Hyde told BuzzFeed News. The journal shouldn’t have accepted the study in the first place if it disliked how it was done, she said.
“I thought that’s what peer-reviewing was for — to critique whether something was strong enough or interesting enough to run or not,” she said in an interview. “We did go through a peer-review process and that’s why it’s so disappointing what’s happened here.”
Independent experts on the microbiome agree that the journal deserves blame too. They point to a bevy of problems, including a small sample size and lack of a control group, made worse by the fact that the flimsy data pushed Hyde’s commercial interests.
“It’s all marketing — it’s all fluff and no substance,” David Relman, a microbiologist at Stanford University, told BuzzFeed News. “It should never be called a microbiome study, but more importantly it’s just a bad study.”
The microbiome is one of the most buzzed-about areas in science, attracting hundreds of millions in federal funding and millions more in private investment. Countless inventions claim to harness the microbiome in some way — from skin care products to drugs, supplements, and superfood regimens.
The fervor often turns into hype that outstrips what the research says, according to Jonathan Eisen, a microbiologist at University of California, Davis, who regularly gives out “Overselling the Microbiome” awards on his blog.
It’s clear that the microbiome is linked in some way to your health: If you go from being a vegan to a carnivore, the microbes in your gut will change. But they also change if you switch up your water source or work out more, Eisen says. Unclear are what all these constant changes actually mean for your body.
“Is it predictable how it changes, and is the change in anything that somehow affects the health or well-being of that person?” Eisen said. “That’s where there’s just much less data.”
Hyde has published two books: The Gut Makeover — first in the United Kingdom in late 2015, and since then in the US and Canada — and an accompanying volume of 100 recipes. She’s talked up the Gut Makeover on Good Morning America and to People, the Daily Mail, and the Telegraph. At her Gut Makeover retreats, at a five-star villa on the Mediterranean island of Menorca, visitors enjoy diet-compliant gourmet meals, Pilates sessions, facials, and one-on-one nutrition talks, all for about $3,000 a person, according to her website. (Hyde said that so far, about 20 paying visitors have attended.)
“A healthy microbiome keeps weight and digestive symptoms down, mood and energy up,” Hyde writes on her website. “In fact, your gut is now dubbed your ‘second brain.’ No wonder many people find mental clarity comes with feeding it right!”
Her monthlong regime is “not for sissies,” as People put it. No alcohol, sugar, caffeine, grains, or dairy (at least at first). Protein at each meal, a total of seven cups of vegetables and fruits a day, and 20 to 30 different types of plants over the course of a week. Three meals a day, a 12-hour fast overnight — and no snacks.
This diet isn’t exactly novel, experts say, and has tenuous links to the microbiome. “You don’t need to know anything about the microbiome to know you should avoid refined sugar and eat a lot of fruits and vegetables,” Rob Knight, a UC San Diego professor and cofounder of the American Gut Project, a crowdsourced microbiome research effort, told BuzzFeed News by email.
But Hyde said that’s a matter of personal opinion. Elements of her program — fasting, plant diversity, prebiotic and probiotic fermented foods — are all backed by research, she said. Critics who think it isn’t novel, she added, “obviously haven’t read the paper itself and they’re not up-to-date with the microbiome research.”
In her just-retracted study, the 21 dieters (half of whom were Hyde’s clients) filled out questionnaires about their health — from weight and digestive pains to energy and anxiety levels — before and after the four-week program.
By the end of the study, the dieters lost an average of 7 pounds. Many of the volunteers also reported improvements in gastrointestinal symptoms, such as loose stools, constipation, bloating, and heartburn, as Hyde blogged and tweeted about.
This “easily implementable” diet, Hyde and Lawrence wrote, “has the potential for improving physical and emotional wellbeing in the general population and also for being used as part of a treatment protocol for conditions as diverse as [irritable bowel syndrome], anxiety, depression and Alzheimer's disease.”
Eisen strongly disagreed. “This is offensive and dangerous,” he said.
He isn’t the only critic. No sooner did the study appear on the journal’s website last summer than it faced backlash.
One critic came from inside PLOS One itself. Duane Mellor, a senior lecturer in human nutrition at Coventry University in England, was so outraged by the paper’s publication that he quit his job as a volunteer editor.
“I saw it and went, If this is the rubbish you publish, I’m not interested,” Mellor told BuzzFeed News.
Chief among Mellor’s complaints, which he rattled off in an email to a PLOS One staff editor, was that the study clearly seemed like a clinical trial to him, but it had not been registered as such, as required.
The editor, Sara Fuentes Perez, didn’t agree. “In this occasion and after discussion with the Academic Editor, we took the position that it did not fulfil [sic] the requirements for a clinical trial, but we will be further discussing this with the Academic Editor,” Fuentes Perez replied in a June 2017 email that Mellor shared with BuzzFeed News.
Over the subsequent months, however, the journal editors decided the paper had enough problems to merit a retraction, as explained in a notice published last week.
For one, the study had no control group of nondieters. Nor were the dieters “blinded” as to what they were doing, to lower the chances that they’d be swayed by the power of suggestion. The researchers didn’t measure anything themselves, but instead asked the dieters to self-report changes in their weight, mood, and other symptoms. Self-reports are often inaccurate — as Eisen noted, who hasn’t fudged their weight? What’s more, the researchers had no way of knowing whether the dieters were actually sticking to the diet.
These issues “call into question the validity of the study and its conclusions which the peer review process did not adequately address,” the retraction notice stated.
PLOS One spokesperson David Knutson told BuzzFeed News that the journal cannot discuss the “confidential” process in which anonymous experts reviewed the study. But, he wrote, because of this case, “we are enhancing our internal editorial scrutiny of manuscripts involving health-related interventions.”
Hyde said that if she could do it over again, she would consider changing the paper’s title, “Microbiome restoration diet improves digestion, cognition and physical and emotional wellbeing.”
“Maybe I would change the name — it would be called an audit or something like that,” she said.
Hyde also noted that the small sample size, self-reporting, and other caveats were clearly and repeatedly noted in the paper, as is typical for a precursor to in-depth research.
But Relman, the Stanford microbiologist, said this study was too shoddy to even count as preliminary scientific research. At best, he said, it could have been posted on a website as a proposal for the basis of a study.
“I was just surprised that any reviewer would have taken more than 10 minutes before saying, ‘You can’t publish this, it’s not a real study’,” Relman said.
Hyde told BuzzFeed News that she was not motivated by money — she just wanted “to share the information with the bigger nutrition community.” But, as she disclosed in the study, she had a clear conflict of interest. She’d written the book being tested, and had an inherent financial incentive to prove that it worked.
Financial conflicts aren’t unusual in science, and they don’t automatically invalidate a research finding, Eisen noted. But it’s concerning in Hyde’s case, he said, given all of the study’s other problems.
“When someone has that interest, like this book, and the study has a large number of fundamental flaws, that raises an extra flag,” Eisen said. “It’s the combination of those two things that is extra damaging in this case.”