Some diet trends come and go, but the keto diet has been around for a century. The dietary regimen was originally introduced by doctors as a modern treatment for epilepsy in the 1920s. Since then, however, keto has been recognized by the diet community as a way to achieve quicker weight loss results by restricting carbohydrates. But despite earning praise from athletes and celebrities, the keto diet doesn’t exactly bode well with health officials. In fact, new research shows that going keto can have negative metabolic and microbiome effects on the body.
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On the ketogenic (or “keto” for short) diet, the goal is to consume high amounts of fat, low to moderate amounts of protein, and as little carbohydrates as possible, according to the International Food Information Council’s (IFIC) blog, Food Insight. “A typical ketogenic eating plan aims for about five percent of calories from carbohydrates, 20 percent from protein, and 75 percent from dietary fats,” explains the organization.
Keto-friendly recipes often involve avocado, yogurt, butter, cheese, nuts, oils, and seeds, and sources of protein such as eggs, chicken, grass-fed red meat, and salmon. You won’t find foods rich in sugar or carbs like potatoes, bread products, or sweets.
“By restricting carbohydrates and monitoring protein intake, a ketogenic diet aims to put your body in a state of nutritional ketosis, a metabolic process that increases the production of ketones, which are made by the liver and can be used as the body’s primary energy source. When we are not in ketosis, glucose (derived from carbohydrate intake) is our body’s primary energy source,” per Food Insight.
For some people, this eating plan works—but for others, the keto diet has a serious impact on their health. A new study published in the journal Cell Reports Medicine found that keto dieters are prone to higher levels of cholesterol and reduced favorable gut bacteria
“The ketogenic diet is effective for fat loss, but it comes with varied metabolic and microbiome effects that may not suit everyone,” said University of Bath professor and study co-author Dylan Thompson in a press release.
For the study, researchers assigned 53 healthy adults to either a moderate sugar diet, a low sugar diet, or a keto diet. At the end of the 12-week experiment, it became clear that those on the keto diet were in significantly less healthy shape than they were at the start of the program.
One of the biggest concerns was the spike in cholesterol.
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“Despite reducing fat mass, the ketogenic diet increased the levels of unfavorable fats in the blood of our participants, which, if sustained over years, could have long-term health implications such as increased risk of heart disease and stroke,” explained lead researcher Aaron Hengist, PhD.
Additionally, the keto diet messed with participants’ gut microbiome compositions. Researchers were particularly concerned about the decrease in Bifidobacteria, a bacteria that helps produce vitamin B, lower cholesterol, and prevent harmful bacteria from entering the gut.
“Dietary fiber is essential for the survival of beneficial gut bacteria like Bifidobacteria. The ketogenic diet reduced fiber intake to around 15 grams per day, half the NHS [National Health Service] recommended intake,” microbiome researcher Russel Davies, PhD, said in the press release. “This reduction in Bifidobacteria might contribute to significant long-term health consequences such as an increased risk of digestive disorders like irritable bowel disease, increased risk of intestinal infection and a weakened immune function.”
The keto diet also reduced glucose tolerance and caused a shift in “lipid metabolism and muscle energy use,” per the release.
“If these changes persist when people switch back to a higher carbohydrate diet it could increase the risk of developing type 2 diabetes in the long-term,” noted Professor Javier Gonzalez, who oversaw the research.
Of the three groups, those on the keto diet did lose the most weight. Still, researchers suggest opting for the reduced sugar diet, which still provides weight loss results but “without apparent negative health impacts."
