Clearing up common misinformation about the ketogenic diet

On Nutrition

The ketogenic diet remains popular, and with that popularity comes misinformation about its potential benefits, and even how to follow it. Some of that misinformation comes from how actual scientific research on the diet is interpreted and communicated in the media, including social media.

Last month at the Food & Nutrition Conference & Expo, the annual meeting of the Academy of Nutrition and Dietetics, Jacob Mey, Ph.D., RD, a registered dietitian and ketogenic researcher and assistant professor at Louisiana State University’s Pennington Biomedical Research Center, discussed some of the “data vs. dogma” about the ketogenic diet, starting with the fact that not all ketogenic research is studying the same thing.

First, a definition. Originally developed to treat severe epilepsy in infants and children, the ketogenic diet is very low in carbohydrates and very high in fat, putting the body into ketosis — a state where it converts fat into ketones (a process called ketogenesis), that it can use for fuel in the absence of glucose (blood sugar). However, Mey said different researchers use widely varying definitions of “low carb.” He also said that how researchers induce ketosis varies.

While many studies use an actual ketogenic diet, others use dietary supplements such as medium-chain triglycerides (MCTs) — a type of fat that we digest differently than other fats — or ketone beverages. Some inpatient studies even use intravenous ketones. Each of these methods function through distinctly different mechanisms in the body and has different effects. All this variability in ketogenic research can pose a problem when you search online for information about the ketogenic diet. More on that in a moment. First, let’s talk nutrition.

A ketogenic diet is inherently high in saturated fat, but there are some big differences between what Mey calls a “research-grade” ketogenic diet, and the type of ketogenic diet people might follow on their own. A research-grade diet includes a lot of unsaturated fats — from foods such as nuts and seeds, avocado, olive oil and fatty fish — along with non-starchy vegetables (think leafy greens, broccoli, cauliflower) and some fruit, primarily berries. But many people view a ketogenic diet as a “bacon, butter and beef” diet, he said, adding that while the ratio of macronutrients (carbs, protein, fat) may look very similar on both diets, the food variety is quite different.

So what are the potential benefits of a ketogenic diet? That depends on who you ask. Circling back to the potential problem of looking for answers online, Mey said he asked an artificial intelligence (AI) app, “Does ketogenesis impact energy balance or metabolic health?” The AI summary — which included one commercial book and one nonexistent research study in its references — reported that ketogenesis significantly increases metabolism, that ketogenic diets decrease both appetite and calorie intake, and that the diet is effective for weight management and improving metabolic health. However, he said that’s not what an expert review of available research found.

That review found that when ketosis was induced by diet, it doesn’t have a major effect on calorie intake or metabolism. When it’s induced by drinking MCT or ketone supplements, there were decreases in both calorie intake and appetite, which lead to a modest weight loss of around two to four pounds over the course of a year — but it’s unclear if this was because of ketosis or because of nausea from drinking oil or ketones. The bottom line was that ketogenic diets are a viable strategy to manage diabetes, metabolic health and weight, but are not necessarily superior to diets that are higher in carbohydrates.

Mey said he’s recommended keto to fewer than 5% of people he’s provided nutrition counseling to. That surprised me, but what really caught my attention was when he said it concerns him when someone decides to follow a ketogenic diet, but only Monday through Friday. Because I’ve observed many people who are “doing keto” but taking breaks from it to eat more carbohydrates on weekends, trips, vacations and birthday parties, I followed up with him to ask about the potential harms of this pattern.

“When your body does that shift to using fats as its primary fuel source after about six to seven days on keto, you become less able to tolerate carbohydrates,” he said, explaining that when someone on a ketogenic diet does eat more carbohydrates than is recommended, their blood sugar will have a bigger spike than someone who regularly eats a higher-carbohydrate diet would experience. This can negatively affect health down the road.

Mey also said that research has found that diets that have roughly equivalent percentages of carbohydrates and fat tend to be worse for health, and if someone follows a ketogenic diet during the week, then eats a higher carbohydrate diet on the weekend, over the course of a week it averages out into “this really awful mix of high saturated fat and carbohydrate mixed together.”

I also asked Mey for his definition of a ketogenic diet. He said he looks at what is palatable to the average person, and, importantly, what they can stick with. “How do you make a diet that’s ketogenic and also tastes good and has different textures?” He said what tends to work is a ratio of 10% (or fewer) calories from carbohydrates (dispersed throughout the meals, not eaten all at once), about 65-70% calories from fat, and about 20-25% from protein.

His bottom line about following a ketogenic diet is, “If you’re going to do it, be compliant on it, and if you’re not, it’s probably not for you.” He also recommends sticking with the diet for at least six months so you can fairly decide if you’re getting the health benefits you hoped for — and working with a dietitian who is experienced in the diet. “There is too much misinformation about it. The gap in knowledge isn’t getting knowledge, it’s in synthesizing it.” And don’t look to AI to do that for you.