UPDATED BY FRANZISKA SPRITZLER, RD, CDE, on July 11, 2024
A common concern about starting a ketogenic diet is that consuming more fat will raise cholesterol levels, potentially increasing the risk of heart disease.
This article separates fact from the fiction, explaining why this concern is often misguided and how eating a very-low-carb, high-fat diet may actually improve your lipid profile and reduce your risk for cardiovascular disease.
What is Cholesterol and What Role Does it Play in the Body?
Cholesterol is a waxy substance that is made in the liver and other cells of your body. It’s also found in many animal foods –– such as eggs, meat, cheese, and butter –– although only a small portion of the cholesterol in your blood comes from the food you eat.
Cholesterol plays several important roles in the body, including maintaining cell membrane integrity and fluidity; synthesizing steroid hormones like estrogen, testosterone, cortisol, and vitamin D; and creating bile acids for absorbing fat-soluble vitamins. Indeed, without cholesterol, the body would be incapable of proper cellular development and intercellular communication.
How to Interpret Lipid Panel Test Results
There are several different lipids in the body, most of which contain cholesterol. The ones you hear discussed the most are the ones in a standard lipid panel.
The main components of a lipid panel lab are:
- Triglycerides
- High-density lipoprotein (HDL) cholesterol
- Low-density lipoprotein (LDL) cholesterol
- Total Cholesterol (includes both LDL and HDL cholesterol)
Triglycerides
Triglycerides are fats that the body can use for energy or store for future use. They are transported in the blood by lipoproteins, which also carry cholesterol. Elevated triglyceride levels are linked to increased cardiovascular risk. When excess carbohydrates are consumed, the body converts them into triglycerides for storage. A ketogenic diet often results in lower levels of triglycerides due to significantly reducing carbohydrate intake.
The normal range for triglycerides is considered less than 150 mg/dL (1.7 mmol/L) but ideally less 90 mg/dL (1.02 mmol/L).
HDL Cholesterol
Low levels of HDL cholesterol –– often referred to as “good” cholesterol –– are associated with increased risk of coronary artery disease. Ketogenic and low-carb diets tend to increase HDL cholesterol levels.
The normal range for HDL cholesterol is 40 mg/dL (1.03 mmol/L) in men and 50 mg/dL (1.3 mmol/L) in women, but ideally > 60 mg/dL (1.55 mmol/L).
LDL Cholesterol
In several studies, elevated levels of LDL –– often referred to as “bad” cholesterol –– have been linked to a greater risk of developing heart disease.
An LDL level below 130 mg/dL (3.36 mmol/L) is considered normal, while the ideal level is under 100 mg/dL (2.6 mmol/L).
Some people who switch to a ketogenic diet experience a significant increase in LDL cholesterol levels (over 200 mg/dL or 5.17 mmol/L). The Lipid Energy Model proposes that this rise, primarily seen in lean individuals, is due to metabolic changes that lower triglycerides and raise both HDL cholesterol and LDL cholesterol. However, the implications of highly elevated LDL cholesterol in those on a ketogenic diet are still under study.
Also, not all LDL is created equal. More on this shortly.
Total Cholesterol
Total cholesterol isn’t very useful for assessing coronary disease risk because it includes both HDL and LDL. Most healthcare guidelines set acceptable total cholesterol levels below 200, reduced from 300 in 1996 when statins became available.
The above are the primary components of a typical lipid panel. However, it’s not the whole picture. Standard panels do not include VLDL (very low-density lipoproteins) or LDL particles.
VLDL
The liver produces VLDL particles that are high in triglycerides and low in cholesterol. VLDLs transport triglycerides to tissues for energy or storage and convert into LDL as they release their triglycerides. As triglyceride-rich lipoproteins, VLDLs increase cardiovascular disease risk, potentially more than LDL. Insulin-resistant conditions like type 2 diabetes often elevate VLDL levels, which can be reduced by very-low-carb diets.
Normal VLDL levels are generally below 30 mg/dL (1.7 mmol/L).
Size Matters with LDL Particles
Identifying LDL particle size can help assess risk for atherosclerosis, a disease in which plaque builds up inside your arteries. This is because small LDL particles have a stronger association with the development of coronary artery disease compared to large LDL particles. Small particles carry less cholesterol, are prone to oxidation, and pose a higher cardiovascular and metabolic disease risk than large particles. Ketogenic diets have been shown to lower small LDL particles.
The target for small LDL particles varies among different laboratories but is generally < 500 nmol/L.
Why isn’t LDL particle size being more widely evaluated and discussed? The most logical answer is cost; evaluation of different types of LDL can be quite expensive. The conventional thinking is that by lowering your total LDL cholesterol, you should lower your small LDL particle concentration and therefore decrease risk for coronary artery disease. However, patients on statin therapy may achieve LDL cholesterol targets yet still have elevated small LDL particles.
Facts vs Fiction
To summarize, it’s important to look at the entire lipid profile rather than one portion (LDL cholesterol) in isolation. Research shows that a low-carb or ketogenic diet may reduce risk factors for coronary artery disease by lowering triglycerides and increasing HDL cholesterol. Slightly higher LDL cholesterol is typically offset by having lower VLDL and fewer small LDL particles. Significant increases in LDL cholesterol warrant a discussion with a doctor who understands ketogenic diets.
