How the Ketogenic Diet Affects Your Heart Health

The ketogenic (“keto”) diet is a popular method for quick weight loss. It promotes eating a diet very high in fat and very low in carbohydrates, one of the three key macronutrients your body needs.

While the keto diet has helped many people lose weight, the implications of following the diet long-term are concerning. Mary Hyer, RD, LDN, CCRP, a Mass General Brigham cardiac rehabilitation dietitian, works with patients at the Elfers Cardiovascular Center at Newton-Wellesley Hospital. She helps heart patients develop healthy eating habits.

Hyer points out a 2019 study from the American College of Cardiology showing that people whose carbohydrate intake was 44% or less of overall calories had an increased risk of irregular heart rhythms. In 2018, another meta-analysis of multiple studies showed low carbohydrate diets are associated with early death from heart and blood vessel disease, according to Lancet Public Health.

A ketogenic diet allows for about 10% of overall calories to be carbohydrates. This extreme restriction can have a ripple effect on your heart and overall health.

How does the ketogenic diet work?

Most people decrease their overall calories and their intake of ultra-processed foods when they restrict their carbohydrates (sugar molecules that provide energy). This helps them lose excess weight quickly.

Hyer notes it’s safe for some people to follow a ketogenic diet for a short time to jump start weight loss. However, a ketogenic diet doesn’t work long-term for most people. For some, especially those with heart problems, following a keto diet can increase health risks.

Glucose, the sugar your body gets from carbohydrates, is typically your main source of energy. When you eat a ketogenic diet, you force your body to switch its fuel source to fat. This is known as being “in ketosis.”

“You can see why heart problems happen in these cases, because your body undergoes a big metabolic change,” says Hyer. “Keto is a huge shock to your system.”

How does a low-carbohydrate diet affect your heart?

A ketogenic or low-carb diet has multiple effects on your heart and body:

Increased low-density lipoprotein (LDL) cholesterol

In order to eat enough fats, many people on the keto diet eat high amounts of butter, cream, and fatty meats. A diet high in these sources of saturated fat correlates with higher levels of cholesterol called low-density lipoprotein (LDL) cholesterol. High LDL cholesterol is associated with poorer health outcomes, contributing to your risk of heart disease, stroke, and other cardiovascular problems.

A rise in LDL is particularly concerning for people with existing heart disease or increased cardiovascular risks. In some people, LDL increases to very high levels when eating a ketogenic diet.

Electrolyte and hydration problems

Electrolytes are minerals that are crucial for many of your body’s functions, including muscle control, nerve health, and hydration. When you reduce your carbohydrate intake, your body doesn’t produce as much insulin, a hormone that helps retain electrolytes.

Electrolytes also play a role in sending the signals that control your heart rhythm. Electrolyte imbalances can interfere with your heartbeat and contribute to irregular rhythms.

Insulin resistance

Your body breaks carbohydrates down into glucose, which increases your blood sugar. Your pancreas produces insulin, which helps regulate your blood sugar. When you limit carbohydrates long-term, your pancreas doesn’t produce as much insulin. This can lead to better blood sugar control in the short term.

However, when you start eating carbohydrates again after long-term restriction, you may develop insulin resistance. This means your body doesn’t respond to insulin like it used to. For most people, this side effect lasts only short-term. But if you already had insulin resistance, it can return or even worsen after stopping a ketogenic diet. Insulin resistance increases your blood sugar levels and can raise your risk of developing type 2 diabetes.

Carbohydrate intake for heart health

Most people should aim for carbohydrates to make up about 45% to 60% of their daily calories.

And the types of carbohydrates you eat matter.

Eat whole foods high in fiber

“Whole foods contain soluble fiber, which takes longer to digest,” Hyer explains. “These fibers help to lower cholesterol, manage blood sugar, and make you feel satisfied after eating.”

Focus on these whole foods:

• Fruits
• Vegetables
• Legumes
• Whole grains

Limit refined carbohydrates

In contrast, limit refined carbohydrates, which are digested more quickly. These include:

• Desserts
• Pancakes
• Pastries
• Waffles
• White bread
• White rice

When you eat these foods, your body secretes more insulin more quickly, which causes an energy rush, then a significant drop.

Healthy eating for a healthier heart

In general, Hyer cautions patients, especially those with heart disease, against any diet or exercise plan that promotes extreme restriction. Instead, she emphasizes moderate changes that you can sustain long term. Over time, these changes can help you manage heart symptoms and possibly even reduce reliance on medications.

“It’s not easy to prioritize healthy eating under the influence of our Western diet and food supply,” she says. “However, small changes can help you take back control and make a big difference in your health.”