Nutrition experts share why they think keto is one of the worst diets — even the less restrictive ‘modified’ version

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Many fast-food restaurants, including Wendy’s (pictured), offer keto options. Erin McDowell/Business Insider
  • The high-fat, low-carb keto diet tied for second-to-last place among 39 diets in US News & World Report’s annual rankings.
  • Despite increasingly popularity and ongoing, often encouraging research, experts say it can be risky to physical and mental health.
  • The diet is also difficult to widely endorse when compared to those that can benefit nearly anyone, but it may help some people, like those with diabetes.
  • “Modified keto,” new to this year’s rankings, also got a low score, with one outside expert telling Insider modifying keto makes it no longer keto.
  • Visit Insider’s homepage for more stories.

Keto, the hugely popular high-fat, low-carb diet, remains controversial after an annual diet roundup ranked it among the worst diets of 2021, according to a panel of experts. It was named the worst out of 39 diets for healthy eating, and tied with the GAPS diet, an elimination diet, for second-to-last place overall.

Even its less restrictive version, modified keto, fared poorly, coming in at 37th for healthy eating and 35th overall. This was the first year US News included modified keto in the ranking.

But the diet is as popular as ever, and emerging research and anecdotal evidence suggest it may benefit from populations. Insider talked to dietitians about why keto remains a professional outcast.

How proponents defend keto

Going keto requires dieters to consume about 70% of their calories from fat and almost no carbohydrates. This prompts the body to enter “ketosis,” in which it burns fat for energy instead of glucose, which is generated from carbohydrates.

Advocates of such patterns have argued that US News’s ranking, which has long shunned keto, is overly reductive. And, plenty of anecdotal evidence suggests that, when done properly, people have enjoyed benefits of keto for years, including weight loss and more energy.

“The problem is we’ve been taking diet advice from lean and healthy people,” Gary Taubes, author of “The Case For Keto” who finally lost weight on the plan after years of unsuccessful dieting, previously told Insider. “My argument is if we do what they do, we get hungry and fatter, so we can’t do it.”

In the past year alone, more research has demonstrated promise for keto.

A November 2020 analysis found the diet could help people with diabetes control blood sugar, lose weight, and improve insulin sensitivity. Two 2020 case reports suggested the diet helps improve sperm count and quality. And, a woman with diabetes who tried keto and intermittent fasting found the plans controlled her diabetes, even though she didn’t lose weight.

And, while critics call the diet unsustainable, some find its binary nature easier than attempting to moderate. “If you tell [men] to live on steak, eggs, and bacon, they’re pretty happy about it,” Taubes said, “at least for a while.”

One of the biggest concerns about keto is the lack of long-term data

While the diet isn’t new — it’s been used for decades in clinical settings, mostly to treat hard-to-control seizures in children — it’s only entered the mainstream in the past few years. As such, when the government released its latest edition of Dietary Guidelines for Americans in late December 2020, its scientists concluded they didn’t have enough research to make a recommendation about it.

“In some ways, it’s not necessarily the fault of keto itself [that it ranks poorly], it’s that we still lack long-term evidence on what a high-fat diet will do for chronic disease risk and longevity,” registered dietitian Kristin Kirkpatrick, who wasn’t involved in the rankings, told Insider when they were released last year.

Intermittent fasting food health

Pros say keto is nutritionally incomplete and has health risks

After 2020, “I think we can all agree though that we want to get back to a more balanced lifestyle — and the keto diet is anything but balanced,” in part since it eliminates healthy, nutrient-rich whole-grain carbs, registered dietitian Bonnie Taub-Dix, author of “Read It Before You Eat It: Taking You from Label to Table,” told Insider.

The diet’s high saturated fat content was of particular concern to US News experts, who called keto “extremely incomplete” in the nutrition category. “Any diet that recommends snacking on bacon can’t be taken seriously as a health-promoting way to eat,” one expert said, according to US News.

Keto can also be unsafe, particularly for people with severe diabetes, kidney disease, and heart disease. One small February 2020 study also linked it to more injury-prone bones in athletes.

The diet can also be dangerous for people at risk of eating disorders, since restrictive diets can fuel anxiety, overeating, bingeing — and eventually, weight gain. “This has nothing to do with a lack of ‘willpower’ but instead is our body trying to keep us alive,” registered dietitian Alissa Rumsey, author of “Unapologetic Eating,” told Insider. “Yo-yo dieting … is more detrimental to a person’s health than staying at a higher weight.”

Keto diet david harper

The diet may benefit some people, but official rankings are designed to look at what benefits most people

There is evidence that keto can improve the health of specific groups of people by improving blood sugar control, as well as helping with weight loss for people who “gain weight easily,” according to Taubes. It also may help regulate mood among people with bipolar 2 disorder and help people regulate their energy by cutting down on sugar, Babita Spinelli, a licensed psychotherapist, told Insider.

But US News rankings and government recommendations endorse eating patterns that benefit almost everyone, not a select few, hence keto’s continuously low standing.

Modified keto is an oxymoron, one expert said

Even a less restrictive version of keto didn’t win experts over.

Modified keto is “an oxymoron,” expert panelist Kathie Beals, a registered dietitian and associate clinical professor at the University of Utah, told Insider. “For you to be in the degree of ketosis for keto, it has to be very low carbohydrate, low protein, super, super high fat, and anything other than that is not keto. So you can’t have a modified keto.”

Still, some people may benefit from modified keto — if, for example, it prompts them to eat more vegetables and less sugar, and they can commit to the pattern long-term.