What are the long-term effects of a ketogenic diet?

The keto diet has gained in popularity in recent years and has many people cutting back on carbs in favor of high-fat foods. Despite its popularity, many health experts have spoken out against the diet, while many others have touted its health benefits.

In fact,  INSIDER ranked it third among diets that millennials planned to try in 2019, for example.

And while most people on this now mainstream ketogenic diet are too thrilled with the weight loss and extra energy to worry too much about the future, the long-term effects of keto are important. And according to multiple experts, keto may not be beneficial in the long run, at least not when compared with other options for maintaining long-term health.

A short history of recent keto popularity

The idea of keto really seized hold in 2014 or 2015, registered dietician and nutritionist Kristen Mancinelli told Well and Good, when the link between saturated fat and heart disease fell under scrutiny. All the meta-analysis "basically came up with no link," said Manicelli, who is the author of The Ketogenic Diet: A Scientifically Proven Approach to Fast, Healthy Weight Loss. "In the nutrition and medical science community, there was a slow move towards saying, 'Okay, villainizing fat is actually having this unintended result of making people over-consume carbohydrates.' That really was the foundation."

According to Dr. Josh Axe, a clinical nutritionist and author of "Keto Diet: Your 30-Day Plan to Lose Weight, Balance Hormones and Reverse Disease," people who adhere to the diet to lose weight commonly see results within a week or two. Well and Good also cited benefits from keto, ranging from increased energy to improved Type 2 diabetes symptoms.

According to University of California San Francisco experts, ketogenic diets are accepted as being beneficial to those suffering from epilepsy or other neurological ailments and may even reduce inflammation in the brain.

But do the benefits all continue when people follow ketogenic guidelines for the long-term? That is where the experts part ways.

Is keto more hype than help?

The Mayo Clinic is the most aggressive in its anti-keto stances, calling the diet "more hype than help."

Mayo quotes its own expert, Dr. Donald Hensrud,  author of "The Mayo Clinic Diet Book". He described people who go on keto or any other restrictive diet. "They want an easy way out," Hensrud said. "They want the magic panacea."

And while decreasing carbohydrate intake dramatically will make a body burn fat and drop weight, problems arise after the initial weight loss, Hensrud said. "Long term, it's hard. People miss some fruits, different vegetables, grains. It's hard. It becomes a very restrictive diet. So although people lose weight initially, maintaining it and keep it off long term is a real challenge on a keto diet."

Hensrud recommended exercise, portion control and increasing fruits, vegetables and whole grains in the diet for long-term health.

Bonnie Taub-Dix, a registered dietitian and certified dietitian-nutritionist, also told Well and Good that she's against keto long term or even for a short while. "This is just another fad diet," she said. "Carbs are not bad for you," she says of the food group demonized by devout keto followers. "They've really gotten a bad rap over the years, but it's more about choosing the right carbs."

Dr. Ethan Weiss is an associate professor at the Cardiovascular Research Institute and studies how diet impacts weight and heart health at the University of California San Francisco. In a university blog, he asserted that the keto diet is "incredibly powerful. Cutting back on carbohydrates, there are so many metabolic benefits. The body processes the remaining carbohydrates more efficiently, and so it requires much less insulin."

But even with that strong claim, he still urges consumers and the medical community to adopt a "wait and see" attitude towards the long-term effects of the keto diet.

Such claims as improved kidney function or even cognitive boosts are not ready for prime time yet. "We just don't have the data on that yet," Weiss said.

He and fellow UCSF ketogenic researcher Dr. Raymond Swanson, a professor of neurology, agree that the diet does not have inherent dangers. But, he cautioned, "there are lots of things that change how medicines work in our bodies, and nutrition is definitely one of them. If you're making a real change in your nutrition, you really should talk to your doctor."