A new study from the American College of Cardiology has found that the popular ketogenic or "keto" diet may contribute to higher levels of "bad cholesterol" and a twofold increase in the risk of heart attacks and strokes. 
“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,” said Dr. Iulia Iatan, MD, PhD, lead author of the study and attending physician-scientist at the Healthy Heart Program Prevention Clinic in St. Paul’s Hospital.
“To our knowledge, our study is one of the first to examine the association between this type of dietary pattern and cardiovascular outcomes.”
The study points out that depriving the body of carbohydrates such as bread, pasta, and rice forces the body to break down fat for energy instead. This breakdown produces ketones in the liver, hence the name keto. Advocates for this type of diet suggest obtaining 60 to 80 percent of calories from fat. 
By comparing this low-carbohydrate, high-fat (LCHF) diet with a more standard diet, the study found that it elevated levels of LDL cholesterol in some people, which is known to elevate the risk of heart disease. 
Before starting this dietary pattern, they should consult a healthcare provider," Iatan said. "While on the diet, it is recommended they have their cholesterol levels monitored and should try to address other risk factors for heart disease or stroke, such as diabetes, high blood pressure, physical inactivity and smoking.”