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Is The Keto Diet Bad for Your Heart?

Medically reviewed by Lisa Booth, RDN
Written by Emily Brown
Posted on May 8, 2024

You’ve surely heard people rave about the keto diet as a way to lose weight, but is it bad for your heart? Living with heart disease often means being mindful of foods to eat and foods to avoid to promote cardiac health. It can be hard to know which diets to follow, if any. The keto diet may have short-term health benefits for some people, but key parts of the diet go directly against guidelines for a heart-healthy diet.

Learn more about the keto diet and heart health, including risk factors to consider for people with heart disease.

What Is the Keto Diet?

The ketogenic diet (keto diet) is a low-carbohydrate, high-fat diet that has been used for a long time to treat diseases like epilepsy and diabetes. The keto diet is different from other low-carb diets because it focuses on eating a lot more fat. In a keto diet, 70 percent to 80 percent of your daily calories should come from fat. For reference, the Dietary Guidelines for Americans 2020-2025 recommends that 20 percent to 35 percent of your daily calories should come from fat.

The idea of the keto diet is to use fat instead of carbohydrates for energy. Carbohydrates break down into glucose, which is the main source of energy for all cells in the body. When the body doesn’t have enough glucose, it breaks down stored fat into ketones for energy. The keto diet is named for these ketones, which have possible benefits such as promoting weight loss, yet the research is still limited. When your body is using ketones for energy, it’s called ketosis.

The Keto Diet and Heart Disease

Short-term studies have shown that the keto diet can improve some risk factors for cardiovascular disease, such as:

  • High-density lipoprotein (HDL) cholesterol (the “good” cholesterol)
  • Body weight
  • Blood glucose levels
  • Triglycerides (fat in blood)

However, other studies have found conflicting results. For instance, a review of available studies from the journal Circulation found that most of the improvements noted above were not maintained after one year.

More research is needed to better understand whether the keto diet is helpful in the long term, especially for people who have heart disease or are at risk of heart disease. Below, we discuss some factors to know about the keto diet and heart health.

Weight Loss

The keto diet has been shown to help with short-term weight loss. There are several ways the keto diet is thought to promote weight loss, such as by reducing food cravings after eating foods with high-fat content.

Losing weight may be beneficial for some people with heart disease because being overweight can increase the risk of high blood pressure and high cholesterol. However, research on weight loss from the keto diet is limited to the short term, meaning it’s unknown how weight may change over the long term. In addition, weight loss on the keto diet may create new problems. For example, even if you lose weight on the keto diet, your cholesterol levels may still go up.

Unhealthy Amounts of Saturated and Trans Fat

Because the keto diet is rich in fat, following the diet usually means that you end up eating more saturated fat. In fact, the keto diet encourages high amounts of saturated fat, such as from butter and palm and coconut oils. And it doesn’t discourage protein sources high in saturated fat, such as pork, bacon, and beef, which cardiologists recommend limiting for those at risk for heart disease. For example, the American Heart Association (AHA) recommends choosing lean meats to reduce the amount of saturated fat you consume.

Eating a lot of saturated fat and trans fat (found in fried foods, margarine, and baked goods) may increase your cholesterol and risk for heart disease. Some doctors say the saturated fat intake from the keto diet can reach unhealthy levels, even if you choose all healthy fats, like those found in fish.

Increased Cholesterol

The keto diet has been shown to increase total blood cholesterol levels, including low-density lipoprotein (LDL) cholesterol. LDL cholesterol is known as the “bad” cholesterol, as it can increase your risk for heart disease. A study published in the Journal of the American College of Cardiology found that people on a low-carbohydrate, high-fat (LCHF) diet had significantly higher total cholesterol levels compared to those following a standard diet. Furthermore, severe high cholesterol was almost twice as common in people following the LCHF diet.

This rise in cholesterol can be especially unhealthy for people living with heart disease. When there’s too much cholesterol in the blood, the arteries can become narrowed and less flexible and are more prone to blood clots. This condition increases the risk of having a stroke or heart attack. The study showed that people on the LCHF diet were more than twice as likely to experience serious heart issues, such as heart attacks, strokes, or sudden chest pain, compared to those on a regular diet.

Of note, the LCHF diet in the study was defined as more than 45 percent of daily calories from fat and less than 25 percent of daily calories from carbohydrates. The typical keto diet recommends 70 percent to 80 percent of calories from fat and only 5 percent to 10 percent from carbohydrates. The LCHF diet in the study was considered “keto-like,” and a strict keto diet may have different results. However, it’s important to consider whether the foods the participants consumed were processed versus whole foods, which are better for cholesterol and heart health.

Limited Intake of Whole Grains and Fruits

Although most diets are limiting by nature, the keto diet is especially limiting due to its strict rules on carbohydrate intake. This situation can be problematic, as many healthy foods contain carbohydrates. For example, the keto diet restricts the intake of heart-healthy foods like whole grains and whole fruits because of their carbohydrate content.

The American Heart Association released a statement saying that the keto diet challenges AHA dietary guidelines because of its limit on these healthy foods and promotes eating more animal-based foods. The AHA adds that restricting whole grains, legumes, and whole fruit may lead to nutrient deficiencies and missed opportunities for getting beneficial phytochemicals (protective plant-based compounds) from these foods.

Doctors Don’t Know the Long-Term Impact of Ongoing Ketosis

Doctors note the need for more research on how the keto diet affects health over time. Some say ketones are a backup energy source for the body, and it’s unclear what being in a long-standing state of ketosis from the keto diet can do to the body in the long run.

Some MyHeartDiseaseTeam members are wary of the effects of the keto diet. “As long as a doctor monitors you closely, it may be good for some people, but it scares me,” one member shared. It’s best to seek professional advice if you have questions or concerns about the keto diet.

Talk to Your Doctor About the Keto Diet

Not only is the keto diet unbalanced, but it can be hard to follow because it’s very restrictive. “I’ve been doing keto and thinking it really isn’t a good idea. The other day, I fixed a bag of broccoli, 4 cups, and ate the entire thing! I was craving veggies!” one MyHeartDiseaseTeam member wrote.

If you’re thinking about the keto diet, it’s best to talk to your doctor or cardiologist before starting. They can help you assess whether a keto-like diet is a good idea given your health history and heart health.

Your doctor may refer you to a registered dietitian or nutritionist for expert advice on maintaining a heart-healthy diet. “My dietitian said to watch sodium and salt counts. Limit highly processed foods. Try to eat as much fruit and veggies as you can,” one member wrote to another asking about foods that are good for the heart.

The key is to find an eating plan that is both heart-healthy and realistic for you to maintain. Each person is different, and what works for one may not work for another. Consulting with a dietitian can help you tailor a diet plan that’s right for you and easy to stick with.

Find Your Team

MyHeartDiseaseTeam is the social network for people with heart disease and their loved ones. On MyHeartDiseaseTeam, more than 61,000 members come together to ask questions, give advice, and share their stories with others who understand life with heart disease.

Have you talked to your cardiologist about the keto diet? What dietary recommendations work best for you? Share your experience in the comments below, or start a conversation by posting on your Activities page.

    Posted on May 8, 2024
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    Lisa Booth, RDN studied foods and nutrition at San Diego State University, in California and obtained a registered dietitian nutritionist license in 2008. Learn more about her here.
    Emily Brown is a freelance writer and editor, specializing in health communication and public health. Learn more about her here.

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