Everyone knows that keto favorites like bacon and butter are bad for your cholesterol and heart health, right?
According to the American Heart Association, the key to improving cholesterol levels involves swapping out your fatty foods for “heart-healthy” foods like oatmeal, fiber-based cereal, whole-grain toast, and orange juice. This is the biggest argument against the ketogenic diet, but it is a topic commonly misunderstood and backed by unscientific and bias data.
In order to understand your cholesterol levels, how they affect heart health, and where the ketogenic diet fits into it all, let’s break down the facts about cholesterol piece-by-piece.
What is Cholesterol?
Cholesterol is a lipid (fat) compound found throughout your body. Cholesterol is not inherently bad; in fact, the majority (around 75%) of cholesterol you have is made from your own body, not from diet. Your body needs cholesterol and its derivatives for numerous bodily functions including:
Cell Membrane Synthesis: Cholesterol acts as building blocks for cell membranes.
Vitamin D Synthesis: Cholesterol is needed in the skin to synthesize vitamin D.
Steroid Hormone Synthesis: Cholesterol acts as the backbone for hormones including sex hormones like testosterone and estrogen, as well as hormones like cortisol and aldosterone.
Bile Production: Bile salts are synthesized from cholesterol and help break down food. 
What Are the Different Types of Cholesterol?
If you have ever tried to mix oil and water, you know that lipids (fats) and water do not mix. The same properties are true within the body; cholesterol does not mix well in the blood.
Because of the hydrophobic nature of cholesterol, it must be transported via a special carrier called a lipoprotein. Lipoproteins are made of both lipids and proteins, allowing it to travel throughout the body and delivers cholesterol to cells that need it.
Lipoproteins are classified based on their protein and lipid composition; since protein is dense and fats are not, lower density lipoproteins contain more fat and less protein, whereas higher-density lipoproteins have more protein and less fat.
When referring to blood cholesterol levels, it is actually these lipoproteins that are referenced. There are five different lipoproteins:
LDL: This is often referred to as the “bad” cholesterol and stands for low-density lipoprotein. LDL’s job is to transport cholesterol to needed tissues throughout your body; however, LDL is highly vulnerable to oxidation. Oxidized LDL can cause inflammation and cause plaque build-up in arterial walls.
HDL: Often called the “good” cholesterol; HDL stands for high-density lipoprotein. HDL is often seen as the good guy because it transports cholesterol from your body to the liver to either be broken down into waste or recycled. HDL has anti-inflammatory properties and has many benefits for your immune system.
VLDL, IDL, and Chylomicrons: Not as commonly discussed, VLDL is the very low-density lipoprotein, IDL is the intermediate-density lipoprotein, and chylomicrons are small lipoproteins that transport fat throughout the lymphatic system. 
How do Cholesterol Levels Affect Heart Health?
Based on the previous information, it may seem obvious that LDL is bad for heart health and HDL is good, but these values often given during blood tests do not paint the whole picture.
The total amount of cholesterol in HDL and LDL particles holds little value; what really matters is the particle size or how many LDL particles are in the blood and how big they are.
Larger LDL particles are more beneficial because smaller LDL particles are more likely to get into the arterial walls and lead to plaque formation.
This is why a standard blood test can give very little information as to a person’s actual heart health. Next time you are at your doctor’s office, ask for an NMR lipoprofile instead of a traditional blood panel. This type of cholesterol test not only gives total LDL and HDL values but also provides the particle number and size for further analysis.
What Does the Research Say About How the Ketogenic Diet Affects Cholesterol Levels?
It may seem paradoxical that increased fat intake may improve cholesterol levels, but several research papers have shown that the ketogenic diet may actually have positive effects on cholesterol levels. Below are four examples of the ketogenic diet’s ability to improve total cholesterol levels.
This study examined the effects of carbohydrate restriction (carbohydrates accounted for 10% of total daily intake) in cardiovascular health markers in 29 overweight men.
After 12 weeks, the participants showed a significant decrease in total LDL particles, medium LDL particles, small, and very small LDL particles, while also showing an increase in LDL size and large LDL particles. These results are indicative of improvements in cardiovascular health.
In this study, 83 obese patients were fed a ketogenic diet for 24-weeks. Weight, BMI, total cholesterol and triglyceride levels, HD and LDL, and fasting blood sugar levels were measured both at baseline and after the 24-week period.
HDL cholesterol levels increased significantly, whereas LDL cholesterol levels, total triglyceride levels, and blood glucose levels all decreased significantly. 
This study examined 12 considerably healthy men after following a ketogenic diet for 6 weeks. Fasting triglycerides as well as postprandial lipemia and insulin levels decreased.
While total and oxidized LDL did not show statistically significant changes, HDL increased by 11.5% after following the ketogenic diet. Further analysis showed that while LDL amounts did not change, the LDL particle size increased, which is associated with a lower risk of cardiovascular disease. 
This study compared the effects of a low-carbohydrate diet versus a low-fat diet to treat obesity and high lipid levels. 120 overweight and hyperlipidemia patients were placed either on a low-carbohydrate (less than 20g of carbs a day) or a low-fat diet (less than 30% total calories from fat and a 500-1,000 calorie deficit).
After 24 weeks, they concluded that a low-carbohydrate diet was better for weight loss and retention and showed an increase in HDL greater than the low-fat group. Oth serum triglycerides and LDL levels decreased, although not statistically different from the low-fat group. 
What Do You Think About Keto and Cholesterol?
Have you noticed an improvement in your cholesterol levels since you started the ketogenic diet? Let us know in the comments below!
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