Keto and Cholesterol: Low Carb Diet and Heart Health

The keto diet may affect cholesterol levels, but more research needs to be done before we will know how much and under what circumstances. Cholesterol levels are linked to heart disease risk, so it's important to discuss this diet with your healthcare provider before trying it, especially if you have other risk factors.

This article discusses the pros and cons of the keto diet, how it affects cholesterol, and what to eat to protect your heart health.

What Is the Keto Diet?

The keto diet differs from other low-carb diets in that it is much more strict in the number of macronutrients allowed. Macronutrients are carbohydrates, fats, and protein. They provide calories and energy and make up the greatest amount of nutrients people consume.

The keto diet typically limits total carbohydrate intake to only about 5%–10% of your total daily calories, or about 20–50 grams a day. The typical fat intake on a keto diet is around 70%–80% of your total daily calories, with 10%–20% of your daily calories coming from protein.

Does the Keto Diet Work?

In 2019, the National Lipid Association released a position statement on diets low or very low in carbohydrates (including ketogenic diets) and their relation to body weight and other cardiometabolic risk factors.

Based on the evidence reviewed, the association concluded that these diets do yield weight loss but are not superior to other weight-loss diets.  

Low- and very low-carb diets do seem to offer greater benefits for appetite control, reducing triglycerides, and decreasing the need for medication in people with type 2 diabetes. Studies showed mixed results on LDL (bad) cholesterol levels, with some demonstrating an increase.

How Keto Affects Cholesterol 

There has been some research done on low-carbohydrate diets and their effects on cardiovascular health. It can be hard to draw specific conclusions on the topic, though, because many of the studies are older, were short-term (less than two years long), had a small sample size, or examined different variations of very low-carb diets.

Nevertheless, we are starting to understand more about how very low-carbohydrate, or ketogenic, diets may affect cholesterol levels. Below is a summary of some of the research studies.

Low-Calorie vs. Ketogenic Diet

An older, 24-week study done in Kuwait compared a low-calorie versus very low-carbohydrate ketogenic diet in adults with and without diabetes. Dietary counseling was provided at the beginning of the study and on a biweekly basis.

At its conclusion, the study showed both diets resulted in significant weight loss. Also, the very-low-carbohydrate ketogenic diet significantly decreased triglycerides, total cholesterol, and LDL (bad) cholesterol levels, with a noticeable increase in HDL (good) cholesterol levels in the people studied.

Ketogenic Diet in Diabetes

One small study had 11 women with type 2 diabetes follow a ketogenic diet for 90 days. After the 90 days, results revealed an increase in HDL cholesterol, a decrease in triglycerides, and no significant changes in LDL cholesterol among participants. Additionally, the study showed decreased body weight and blood pressure.

Ketogenic Diet in a CrossFit Group

Studying healthy people, a 12-week investigation looked at the effects of a ketogenic diet in people who regularly trained in CrossFit. Twelve people participated in the study involving the high-intensity, interval-training workout. Five of the study participants were in the control group and continued eating a regular diet, while seven people followed a ketogenic diet.

The study concluded that changes in HDL cholesterol and triglycerides were not significant and were similar among participants in both groups. In contrast, LDL cholesterol increased nearly 35% in those following the keto diet along with CrossFit.

Ketogenic vs. Low-Fat and Low-Carb Diets

A 2013 review of studies comparing a very low-carbohydrate ketogenic diet to a traditional low-fat diet showed that participants following the low-carb keto diet experienced decreases in body weight and diastolic blood pressure, along with increases in both HDL cholesterol and LDL cholesterol.

Another review of studies in 2016 comparing low-fat and low-carbohydrate diets yielded similar results. The authors found that participants on low-carbohydrate diets had a greater weight loss and higher increase in HDL cholesterol but also showed higher LDL cholesterol levels than those following a low-fat diet.

Effect of Saturated Fat

A review of low-fat diets versus low-carb, high-fat diets followed for more than 12 months looked at the effects on cholesterol levels in overweight or obese people.

Researchers found that decreases in total cholesterol and LDL cholesterol levels were significantly more noticeable in those following low-fat diets. In contrast, an increase in HDL cholesterol and a reduction in triglyceride levels were more apparent in participants following a high-fat diet. 

Whether cholesterol increases or decreases largely depends on the type of fats consumed when following the very low-carbohydrate ketogenic diet.

The study authors found that decreased total cholesterol levels were associated with high-fat diets that contained a lower intake of saturated fat and higher polyunsaturated fat intake. In comparison, increased HDL cholesterol was related to a higher intake of monounsaturated fat.

Lower saturated fat intake was marginally related to lower LDL cholesterol levels. Additionally, increased triglyceride levels were associated with higher intakes of carbohydrates.

Ketogenic Mediterranean Diet with Phytoextracts

An older Italian study looked at 106 overweight or obese people who ate a diet known as the ketogenic Mediterranean diet with phytoextracts (KEMEPHY) and took a daily multivitamin supplement over six weeks. Subjects were allowed to consume unlimited calories in a diet made up of green vegetables, olive oil, fish, meat, and other high-quality proteins, along with specific food supplements and herbal extracts.

The results showed a significant decrease in body mass index (BMI), total cholesterol, LDL cholesterol, triglycerides, and blood glucose levels. There was also a significant increase in HDL cholesterol levels.

Foods To Choose on the Keto Diet

Consuming mostly unsaturated fats, compared to saturated fats, while on a keto diet may improve cholesterol levels, especially LDL cholesterol levels. Unsaturated fats are found in foods such as:

• Plant oils like olive, avocado, sunflower, corn, and canola oils
• Avocados
• Olives
• Fatty fish, including salmon, sardines, tuna, and mackerel
• Nuts and nut butters, including peanuts, almonds, cashews, pecans, and walnuts 
• Seeds, such as flax, sesame, sunflower, and chia

The keto diet is also typically lower in fiber, so maximizing the small number of carbohydrates allowed while following keto can benefit not only cholesterol levels but also gut health. Choosing non-starchy fruits and vegetables like avocados, tomatoes, asparagus, broccoli, and spinach can help.

Additionally, many people cannot follow the keto diet long-term, so having a clear and defined plan for how to transition off the keto diet is important to help retain any positive health benefits acquired.

Role of Genetics

While the ketogenic diet may be safe for most people, it might not be healthy for others to follow. A ketogenic diet could increase LDL cholesterol levels in some people at high risk for heart attack and stroke.

In particular, people with an inherited condition called familial hypercholesterolemia should always consult with their healthcare provider before trying a ketogenic diet. Familial hypercholesterolemia is marked by very high LDL cholesterol levels and an increased risk of premature heart disease. The American Heart Association has stated that only 10% of people with familial hypercholesterolemia are aware they have it.

Additionally, some people have a rare genetic condition that affects how LDL particles are regulated, causing high LDL cholesterol levels. The genetics causing this response isn’t completely understood, but the APOE gene, which provides instructions for making a protein called apolipoprotein e, may be one of several factors involved. People who have this inherited genetic condition should avoid the keto diet.

Summary

The ketogenic diet is very low in carbohydrates and high in fat. How this affects HDL and LDL cholesterol, triglycerides, and heart health is under investigation. Studies on the connection generally have been short-term and have reached a variety of conclusions.

One factor that affects cholesterol outcomes with keto is the type of fats consumed, with unsaturated fats being preferred. Genetics may also play a role in how the ketogenic diet influences cholesterol levels in an individual.

A Word From Verywell

Close communication with your healthcare professional and regular testing are key factors in starting any new diet regimen, including the keto diet, to ensure a safe path forward. If you choose to follow a keto diet, be sure to check with your healthcare provider first to make sure it is safe for you. Also, get your cholesterol levels tested before and during the diet so you can be confident they aren't changing to unsafe levels. 

If you plan to follow the ketogenic diet only for a short while, make a plan with your doctor on how you should transition off of it to help ensure success in the long term.