Doctors Issue Warning on Keto Diets Following Study on Heart Attack Risk

A low-carb, high-fat (LCHF) “keto-like” diet may double the risk of cardiovascular events such as blocked arteries, heart attack, and stroke, according to new research that was recently presented at the American College of Cardiology’s Annual Scientific Session and World Congress of Cardiology.

LCHF diets, like the keto diet, restrict consumption of carbohydrates that are the body’s primary source of energy. By depriving the body of carbohydrates, it is forced to start breaking down fat for energy instead.

The study was based on information collected by the UK Biobank, a large-scale database with health information from more than 500,000 people living in the United Kingdom. Researchers examined individuals with data on serum lipids, metabolomic markers, and dietary patterns. All participants recorded their diet in a 24-hour food survey and had their blood drawn to measure their cholesterol levels. 

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Among them, 305 met the criteria for an LCHF diet, defined as consuming less than 25 percent of daily calories from carbohydrates and more than 45 percent from fat. The researchers noted that the diet is “keto-like,” due to its higher percentage of carbohydrates and lower levels of fats than a strict ketogenic diet.

They matched these participants with 1,220 individuals who were considered to be on a “standard diet” and made up the control group. Participants’ average age was 54 years, and they had a mean body mass index of around 27—which placed them in the “overweight” category.

The researchers followed the participants for an average of 11.8 years. During the follow-up period, 9.8 percent of participants on an LCHF diet versus 4.3 percent of the control group experienced a cardiovascular event, including blockage in arteries, a heart attack, or stroke. Those on LCHF diets had significantly higher LDL cholesterol levels and apolipoprotein B—a protein that coats LDL cholesterol proteins and can predict heart disease better than elevated levels of LDL cholesterol can.

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Notably, the researchers noticed that the LCHF diet participants’ total fat intake was higher in saturated fat and had double the consumption of animal sources (33 percent) compared to those in the control group (16 percent).

“Our study found that regular consumption of a self-reported diet low in carbohydrates and high in fat was associated with increased levels of LDL cholesterol—or “bad” cholesterol—and a higher risk of heart disease,” lead study author Iulia Iatan, MD with the Healthy Heart Program Prevention Clinic, St. Paul’s Hospital and University of British Columbia’s Centre for Heart Lung Innovation, said in a statement.

Iatan said the findings merit further research in prospectively designed studies, especially when approximately one in five Americans report being on a low-carb, keto-like or a full keto diet. One of the researchers’ next steps will be to try to identify specific characteristics or genetic markers that can predict how someone will respond to this type of diet.

Warning against keto diets for weight loss

With the results of this new study, the Physicians Committee For Responsible Medicine (PCRM)—a non-profit health advocacy organization that combines the expertise of more than 17,000 physicians—called for renewed warnings against low-carbohydrate keto diets, especially considering they are so popular among the general population for quick weight loss. 

“The bubble has burst on low-carbohydrate diets,” Neal Barnard, MD, President of the PCRM, said in a statement.

“Despite the risks of the cholesterol-laden ‘keto diet,’ many people try them in hopes of losing weight. What they lose is their heart health. We need stricter warnings about these fad diets.”  

Low-carbohydrate diets have been popular for decades, starting with the Atkins Diet, the South Beach Diet, and, more recently, keto diets. They greatly reduce healthy fruits, grains, beans, and other carbohydrate-containing foods, replacing them with meat and fats. 

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Medical experts have warned of a variety of risks, including cardiovascular disease and cancer, in addition to weight regain after the diet ends. 

Is a vegan diet better for weight loss?

Instead, the PCRM advocates for a plant-based diet for health and weight loss, and many studies back up this claim.

“Decades of research show that a plant-based diet can help you reach a healthy weight and lower your risk for heart disease, type 2 diabetes, and other chronic diseases,” Vanita Rahman, MD, of PCRM, tells VegNews. “Whether you want to lose weight, maintain a healthy weight, or just eat better, a plant-based diet can help you achieve your goals.”

A study published last year found that a plant-based diet is associated with lower body weight, fat, and waist size compared to meat-eaters. “Plant-based diets can help you lose weight and keep it off because they are packed with fiber, which helps fill you up, without adding extra calories,” Rahman says. “Aim for 40 grams of fiber a day, which is easy to do when you move vegetables, fruits, whole grains, and beans to the center of your plate.”