A common misconception is that the ketogenic diet increases “bad” cholesterol levels and clogs your arteries because it is so high in fat. However, much of the recent research shines light on how high-fat, low-carb diets can optimize your cholesterol levels and in fact improve your heart health. Those in the keto diet group lost more weight, had more significant reductions in triglyceride levels, and had higher HDL cholesterol levels. HDL levels tend to rise when people replace carbohydrates with saturated, monounsaturated, and polyunsaturated fats. It is important to note that the researchers only followed the participants for 6 months. As a result, it is not clear whether or how their cholesterol levels changed later on.
For example, they refer to one study in which participants who had followed the keto diet for 2 months experienced an average rise in LDL cholesterol levels of 0.62 millimoles per liter (mmol/L). Another study showed a decrease of 0.26 mmol/L in LDL cholesterol levels after 6 months.
A Ketogenic Diet’s Connections with Cholesterol
About 32% of men and 13% of women in the US suffer from low levels of HDL cholesterol.  Additionally, the majority of Americans do not have HDL cholesterol levels high enough to decrease the risk of cardiovascular illness. As chronic conditions such as diabetes and cardiovascular illness increase in prevalence worldwide, scientists have evaluated methods to increase levels of HDL cholesterol. For many years, physicians have used drugs called statins to increase HDL .
Recently, scientists have looked at utilizing dietary interventions as cost-effective methods to optimize HDL cholesterol and prevent the onset of cardiovascular diseases. Below we document three research studies examining low-carb and ketogenic diets effects’ on HDL.
Long-Term Impact of Ketogenic Carbohydrate Restriction on HDL Cholesterol
In a study from 2009 by Brinkworth et al., researchers recruited 118 obese men and women and separated them into two groups for a year-long intervention study. The first group consumed a very-low-carbohydrate, high-saturated diet with 4%, 35%, and 61% energy from carbohydrates, proteins, and fats respectively.
This equates to about 20 grams of carbohydrates on a 2000 kcal diet per day – a more stringent application of carbohydrate restriction use than the meta-analysis above. The second group consumed primarily a low-fat diet with 46%, 24%, and 30% energy from respectively from carbohydrate, protein, and fat per day. Both diets contained an equal number of calories. About 59% of participants completed the 12-month trial: 33 in the low-carb group and 36 in the low-fat group. Both groups lost similar amount of body weight and body fat. The subjects who participated in the low-fat intervention experienced an average increase in HDL cholesterol of 0.07 mmol/L from 1.36 mmol/L to 1.43 mmol/L.  This represents a 4.9% increase.
In contrast, the subjects who participated in the high-fat intervention experienced an average increase in HDL cholesterol of 0.30 mmol/L from 1.45 mmol/L to 1.75 mmol/L.  This represents a 20.6% increase – almost four times as much as that found in the low-fat diet.
Because of their findings, diets very low in carbohydrates may have cardio-protective effects compared to low fat diets.
Key Takeaways: Very low carbohydrate ketogenic diets (<20g Carbs) increase HDL levels substantially more than low fat diets do.
Recommendation: If you need to increase your HDL levels, a ketogenic diet can be a useful dietary intervention.