Low-carbohydrate, high-fat diets have become popular ways to lose weight among many Americans, including celebrities like Kim Kardashian and Lebron James.

Published: March 13, 2023 | Updated: August 15, 2024

Low-carbohydrate, high-fat diets have become popular ways to lose weight among many Americans, including celebrities like Kim Kardashian and Lebron James.

A new study, however, shows “keto-like” diets may be linked to a heightened risk of cardiovascular events like chest pain, blocked arteries, heart attacks and strokes.

The results of the study were presented at the American College of Cardiology’s 2023 Annual Scientific Session & Expo Together With World Congress of Cardiology.

Researchers analyzed and compared the diets of 305 people eating a low-carb, high-fat (LCHF) diet, which is considered keto-like, with roughly 1,200 people eating a standard diet.

A low-carb, high-fat diet was defined in the research as a diet with more than 45% of total daily calories coming from fat and no more than 25% coming from carbohydrates. A ketogenic diet is aimed at putting the body into a metabolic state called ketosis, where it burns energy from fat instead of glucose from carbohydrates.

“Diet is a four-letter word,” said Kelley M. McIntyre, M.D., internal medicine physician with Norton Community Medical Associates, who also sees patients seeking medical weight loss. “‘What’s the best diet?’ is always the question that everybody wants to know.”

In the recent study, researchers found, after following the subjects for more than a decade, people who participated in a LCHF diet had significantly higher levels of both low-density lipoprotein (LDL, or “bad”) cholesterol and apolipoprotein B (apoB), the protein that helps carry fat and cholesterol through the body.

“Sometimes I do see the LDL going up [in my patients], the bad cholesterol, with a ketogenic diet,” Dr. McIntyre said. “And oftentimes that could be from the animal fat products, especially full-fat dairy, hamburger, those kinds of things. So I think it’s something to consider, and it definitely could be a concern in certain populations.”

The study also showed people on a LCHF diet had more than two times higher risk of major cardiovascular events, such as arterial blockages requiring stents, heart attacks, strokes and peripheral arterial disease. In total, the researchers found 9.8% of participants on a LCHF diet experienced a new cardiac event, compared with 4.3% of people eating a standard diet.

“That’s why it’s important to discuss diet changes with your physician,” Dr. McIntyre said. ”Because if a patient already has underlying heart disease, or issues like that, or elevated cholesterol — it could possibly raise those, especially if you’re doing a really high animal fat/saturated fat diet.”

Of the participants in the study, 73% were women. The group’s average age was 54.

The study was considered observational, meaning it can show only a correlation between the diets and risks for cardiac events, not causation between the two. However, those who conducted the research believe it merits further research into similar studies.

“The best diet is the one that you’re going to be able to stick with,” Dr. McIntyre said. “So there are lots of studies that have looked at this. And really the bottom line is people can lose weight with any diet,  and the science also supports that people will do better with an eating plan that they can sustain. So that’s a conversation that I have to have with my patients.”

According to the International Food Information Council’s 2020 Food and Health Survey, 43% of Americans reported they had followed a diet in the past year.

Of the responses, a ketogenic (high-fat) diet was the third most-followed, with a 7% follow rate.

To see tips from the American College of Cardiology for a heart-healthy diet, click here.