The ketogenic diet rose to popularity in the early 2000s with the mantra “fat is not the enemy.”

But a study covered in the March 2024 issue of Current Problems in Cardiology suggests that the diet—which focuses on foods high in fats and deemed very low in carbohydrates—is perhaps something of a Trojan horse.

The paper, published by Joanna Popiolek-Kalisz, MD and PhD, found a few issues with the diet’s parameters. The first was weight-loss related: While many people who followed it experienced rapid weight loss (typical of making any significant diet change), it was likely mostly water weight and failed to yield any permanent positive health changes within the body.

“The ketogenic diet does not fulfill the criteria of a healthy diet,” Popiolek-Kalisz states in the paper. Quite the contrary, in fact: When it comes to overall heart health, “the low-carb pattern is more beneficial than very low-carbohydrate (including the ketogenic diet).” Because of the keto diet’s emphasis on fats, those adhering to it typically have a higher rate of LDL cholesterol, which is associated with a higher risk of heart disease, clogged arteries, and death.

Low-carb dietary plans include the Atkins diet, the paleo diet, and the South Beach diet. Other studies have noted that the keto diet can also lead to major vitamin and mineral deficiencies (as well as a surplus of fat-soluble vitamin K, which is also unhealthy for the heart) and increased kidney stones.

According to the International Food Information Council’s annual study, more than half of Americans follow a diet or a specific eating pattern—but the high-fat keto diet dropped in popularity by 4% compared to 2023. That trend will likely continue downward.