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A “keto-like” low-carb, high-fat diet may be linked to higher levels of “bad” cholesterol and doubles the risk of cardiovascular events such as clogged arteries, heart attacks and strokes, according to new research.
“Our study found that regular self-reported consumption of a low-carbohydrate, high-fat diet was associated with increased levels of LDL cholesterol — or ‘bad’ cholesterol — and a higher risk of heart disease,” lead author of the study, Dr. Yulia Iatan with the Healthy Heart Program Prevention Clinic, St. Paul and the University of British Columbia’s Center for Heart and Lung Innovation in Vancouver, Canada, said in a news release.
“This study makes an important contribution to the scientific literature and suggests that the harms outweigh the benefits,” said Christopher Gardner, a professor of medicine at the Stanford Prevention Research Center, who has conducted clinical trials of the keto diet. Gardner was not involved in the study.
“Elevated LDL cholesterol should not be simply dismissed as a minor side effect of a VLCD (very low calorie diet) or ketogenic diet,” Gardner said, pointing to the higher risk of cardiovascular events in individuals with higher blood ketone levels. , compared to those on a more standard diet.
In the study, researchers defined a low-carbohydrate, high-fat (LCHF) diet as 45% of total daily calories coming from fat and 25% coming from carbohydrates. The study, which is not peer-reviewed, was presented Sunday at the American College of Cardiology’s annual scientific session along with the World Congress of Cardiology.
“The rationale for our study came from the fact that we would see patients in our cardiovascular prevention clinic with severe hypercholesterolemia after this diet,” Eathan said during a presentation at the session.
Hypercholesterolemia, or high cholesterol, increases the risk of heart attack or other adverse cardiovascular events.
“This led us to wonder about the relationship between these low-carbohydrate, high-fat diets, lipid levels, and cardiovascular disease. And so, despite that, there’s limited data on that relationship,” she said.
The researchers compared the diets of 305 people eating an LCHF diet with about 1,200 people eating a standard diet, using health information from the UK Biobank database, which has followed people for at least a decade.
Researchers found that people on the LCHF diet had higher levels of low-density lipoprotein, also known as LDL, cholesterol, and apolipoprotein B. Apolipoprotein B is a protein that coats the proteins of LDL cholesterol and may predict heart disease better than elevated LDL cholesterol levels can.
The researchers also observed that the total fat intake of the LCHF diet participants was higher in saturated fat and had double the consumption of animal sources (33%) compared to those in the control group (16%).
“After an average of 11.8 years of follow-up—and after adjusting for other heart disease risk factors, such as diabetes, high blood pressure, obesity, and smoking—people on the LCHF diet had more than twice the risk of several major heart vascular events, such as blockages in arteries that had to be opened with stenting procedures, heart attack, stroke, and peripheral artery disease,” the researchers found, according to the news release.
The researchers said in the release that their study “can only show an association between diet and increased risk of major cardiac events, not a causal relationship,” because it was an observational study, but their findings merit further study, “especially when approx. 1 in 5 Americans report being on a low-carb, keto-like or full-on keto diet.”
Eathan said limitations of the study included measurement errors that occur when dietary assessments are self-reported, the study’s small sample size, and that most of the participants were British and did not include other ethnic groups.
The study also looked at the longitudinal effect of following the diet, while most people who follow a keto-like diet tend to follow it intermittently for shorter periods of time.
Most of the participants – 73% – were women, which Yatan says is “quite interesting to see, but also supports the existing literature that women in general tend to follow more dietary patterns, tend to be more interested in changing you are alive ”
When asked if there were groups that weren’t harmed by following an LCHF diet, Yatan said how long people were on the diet and whether or not they lost weight “could offset any increase in LDL.”
“It’s important to remember that every patient responds differently. So there is indeed inter-individual variability between the response. What we found is that, on average, patients tend to have elevated LDL cholesterol levels,” she said.
Dr. David Katz, a lifestyle medicine specialist who was not involved in the study, said that “there are different ways to formulate an LCHF diet, and it is very unlikely that they will all have the same effect on serum lipids or cardiac events.”
However, he added: “That the LCHF diet was associated with adverse effects in this study is a reality check for those who adopt such diets simply because they are fashionable.”
Most health experts say the modern keto diet, which bans carbs to make your body burn fat for fuel, cuts out healthy foods like fruits, beans and legumes, and whole grains. On the keto diet, you limit your carbohydrate intake to just 20 to 50 per day—the fewer the better. To put that into perspective, a medium banana or apple contains about 27 carbs—the full day’s worth.
“These food groups that must be eliminated to achieve ketosis are major sources of dietary fiber as well as many important nutrients, phytochemicals and antioxidants. This is a cause for concern for many health professionals who believe that a VLCD or ketogenic diet is harmful to health in the long term,” Gardner said.
Keto is short for ketosis, a metabolic state that occurs when your liver starts using stored fat to produce ketones for energy. The liver is programmed to do this when your body loses access to its preferred fuel – carbohydrates – and thinks it is starving.
The keto diet has been around since the 1920s, when a doctor came across it as a way to control seizures in children with epilepsy that didn’t respond to other treatments.
Low-carb diets like keto rely heavily on fat to fill you up. At least 70% of the keto diet will be made up of fat; some say it’s more than 90%.
While you can get all that fat from healthy unsaturated fats like avocado, tofu, nuts, seeds, and olive oil, the diet also allows for saturated fats like lard, butter, and coconut oil, as well as whole milk, cheese, and mayonnaise. Eating a lot of foods high in saturated fat increases the body’s production of LDL cholesterol, which can build up in the arteries and restrict blood flow to the heart and brain.
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