What Happens To Your Heart When You Stop Eating Carbs

"I am cutting carbs." This is a phrase you'll hear from people on high-protein diets like the Atkin's or Paleo diet and from those following a high-fat and low-carb diet like keto. 

There are several reasons why people choose low-carb diets, the most common of which is weight loss. Despite the fact that carbs are the main macronutrient your body uses to produce energy, consuming too much of it can lead to weight gain, obesity, increased blood triglycerides, reduced "good" (HDL) cholesterol, and even metabolic syndrome. So if you're at all concerned about what happens to your risk of heart disease when you reach a particular age, it makes sense to reduce carb intake, right? Well, yes and no, per science. 

For the purpose of clarity, when we say "no carbs or "zero carbs," we're actually referring to low-carb diets. Carbs are divided into refined or unhealthy carbs such as processed food, sugary treats, and simple carbohydrates that cause a faster spike in blood sugar when consumed, and healthy carbs like whole-grains, fruits, and vegetables. Traditionally, lowering your carb intake has been linked with better heart health. Per a 2022 study published in The American Journal of Clinical Nutrition, overweight and obese participants who followed a high-fat and low-refined carb diet saw greater improvement in heart disease risk than those who consumed a low-fat and high-carb diet. But wait a minute — the opposite has been found to be true, too. 

Heart disease risk with low-carb diets

A low-carb and high-fat (LCHF) keto diet was linked with higher levels of bad cholesterol and increased risk of blocked arteries, heart attacks, and strokes in a 2023 study done by researchers at the University of British Columbia.  

"Our study found that regular consumption of a self-reported diet low in carbohydrates and high in fat was associated with increased levels of LDL cholesterol, or 'bad' cholesterol, and a higher risk of heart disease," shared Dr. Iulia Iatan, lead author and physician-scientist at UBC's Centre for Heart Lung Innovation and the Healthy Heart Program Prevention Clinic at Providence Health Care's St. Paul's Hospital. However, the researchers also found that the participants on the LCHF diet were consuming higher amounts of saturated fat, which has been linked with heart disease and stroke risk.

According to Dr. Neel Chokshi, associate professor of clinical medicine and medical director of the Sports Cardiology and Fitness Program at Penn Medicine, consuming the wrong kind of fat can happen with low-carb diets like the keto diet. The keto plan advocates for as much as 90% of your daily calories coming from fat. This sudden increase in fats in your system can result in increased levels of bad cholesterol and triglycerides (at least in the short term) and ketosis, a state in which your body breaks down fat, in the absence of sufficient carbs, into ketones for energy. An elevated heart rate is another side effect of ketosis. Science has yet to fully understand the long-term effects of ketosis. 

What does this mean for heart disease and low-carb diets?

The Mediterranean diet has long been applauded by health professionals as the best diet to mitigate heart disease risk. It's a diet that has plenty of fruits and vegetables, whole grains, fish and seafood, healthy fats, and reduced dairy, meats, and saturated fat. Diversifying your protein sources without only relying on animal sources, by adding legumes, lentils, etc. is also recommended. So is cutting out added sugars, refined carbs, ultra-processed foods, and limiting alcohol consumption. 

In fact, in the aforementioned 2022 study, participants with less heart disease risk on a low-carb diet were also consuming fiber-rich fruits, vegetables, nuts, beans, and lentils. 

Other diets that sit at the top of the "heart-friendly" list include the DASH diet (a balanced diet that promotes eating heart-healthy foods) and the pescatarian diet (a fish, seafood, and plant-based diet), per the American Heart Association. Low-carb/ketogenic diets are actually bottom-tier, mainly because they don't limit saturated fat content. Perhaps the goal is to not slant toward any extremes, as observed by Dr. Neel Chokshi (via Penn Medicine). Look for sustainable diets with a good combination of healthy carbs, lean protein sources, and healthy fats, while avoiding smoking, limiting alcohol, getting sufficient sleep, and consistently exercising. Also, keep an eye out for warning signs of heart disease you shouldn't ignore, like chest pain, shortness of breath, fatigue, and dizziness. If you already have cardiovascular problems, check out the best diet for people with heart disease.