"keto-like" and dislike

Another Flawed Study about Low-Carb-ish Diets

You may have seen the keto diet getting blasted in the news again recently. Several media outlets picked up on a press release out of the American College of Cardiology that seems to show that the ketogenic diet can cause heart disease. But does it? As always, the devil is in the details.

First of all, here’s the study: Researchers pulled data from UK Biobank, a database containing health information from half a million people living in the United Kingdom. They looked at 305 low-carb dieters, and compared them with 1220 people on a standard diet.

They found that 9.8% of the people in the low-carb group suffered a “cardiac event” (heart attack, stroke, etc) in the course of 10-plus years of follow up, compared to 4.3% of the standard diet group — so, double the risk. Yikes!

But before you run screaming, there are a couple of issues that I see with this one.

defining our terms

First, the researchers have creatively coined the term “keto-like diet” to describe the eating pattern that they’ve studied. Definitions are important, and this one especially so.

A ketogenic diet is one that, well, generates ketones. In simple terms, cutting carbohydrates coaxes the body to burn fat for fuel. Ketones are chemicals that are the byproduct of this process, and they supply fuel to the brain.

The thing about ketones is that they can be measured — in the urine, in the breath, or in the blood through a simple finger prick. The usual definition of ketosis is having blood ketone measurements of 0.5 mml/L or higher. If your finger prick confirms a number higher than 0.5, you’re in ketosis.

There are many ways to get into ketosis. Fasting, for example. Restricting carbs to around 20 grams per day. Adding MCT oil to your diet. All of these are ketogenic diets. But however you get there, you’re either in ketosis or you’re not. It’s pretty much black-and-white. In fact, the ketogenic diet is probably the only one that can be measured so objectively.

the keto conundrum

So that’s the “keto” diet? Isn’t it the same thing? Well, yes and no.

The word “keto” has only been around for a few years — first as a handy abbreviation for the word “ketogenic,” but now it’s morphed into a favorite buzzword for food manufacturers. On a recent trip to Costco I saw everything from snacks to meals to desserts bearing “KETO-FRIENDLY” or “KETO-CERTIFIED” right on the front of the package. Great, right? But who’s doing the certifying? No one. These chocolate “No-Sugar Keto Bars,” for example, contain 16g of carbohydrate per serving — which is perfect if a chocolate candy bar is going to be my only meal that day.

Okay, so back to the study in question. If the definition of “keto” is fuzzy at best, then what the hell is “keto-like?” These researchers set the bar at less than 25% of calories from carbohydrates. So for someone eating a standard, 2000-calorie diet, 500 of those calories are coming from carbs. That translates to 125 grams.

In my own experience, going much higher than 40 grams of carbs will drop my ketone levels to 0.5 or below, so there’s no way that I’d be in ketosis eating 125 grams per day. Ryan Lowry, PhD brings it down to earth in this way: a diet of 25% carbs would be three Big Macs per day!

Photo by amirali mirhashemian on Unsplash

going to confession

There’s another issue here. These researchers didn’t actually track what the 305 keto-like dieters ate. The folks in UK Biobank were surveyed once — just once — in a questionnaire that asked what they had eaten the previous 24 hours.

There are some well-established concerns about the validity of self-reported data. Who really remembers exactly what they ate and how much? (How much rice was in that lunch yesterday? A cup? 1.2 cups?) And assuming they do remember, are they always completely honest — with their doctor and with themselves?

But beyond that, the researchers are making the assumption that what these folks ate in those 24 hours are the same things they ate for the next ten years. That’s quite a leap! There’s nothing in the data to indicate that these people stayed on their keto-like diet. It’s quite possible that their eating patterns changed — perhaps several times — during the subsequent decade. To their credit, the researchers acknowledge these limitations, and recommend only that the topic merits further study.

In the end, despite the sensationalist headlines, the only thing this study really shows is that there’s a correlation (not causation) between eating a Big Mac-like diet for one day and developing heart disease 10 years later.

I, for one, wouldn’t bet the farm on that.