Intermittent Fasting May Raise Heart Attack Risk

In recent years, intermittent fasting (IF), also known as time-restricted eating, has gained popularity as a go-to diet strategy for weight loss. There are different ways to try intermittent fasting, but essentially, the idea is to eat all meals during a restricted window of time each day—or on the days you’re engaging in intermittent fasting (some folks take certain days off from IF each week). Some promoters of intermittent fasting recommend limiting the eating window to eight hours or less a day.

And while many sing intermittent fasting’s praises, there are some questions surrounding its safety and efficacy, especially in the long term. For example, we previously reported on a study that suggests that limiting daily eating time to an eight-hour window was associated with a 91% higher risk of heart disease. And another study suggests that skipping breakfast, which can help you stick to an intermittent fasting window, may increase the risk of dementia. 

American and Chinese researchers recently teamed up to dive into intermittent fasting research and see if there’s any connection between sticking to an eight-hour eating window and dying from heart disease or cancer (or dying in general—referred to as all-cause mortality). They published their findings in Diabetes & Metabolic Syndrome: Clinical Research & Reviews. Let’s break down what they found. 

How Was This Study Conducted?

Researchers drew their data from the National Health and Nutrition Examination Survey (NHANES), a U.S. study that ran from 2003 to 2018. NHANES was conducted annually, with information being released every two years. For this study, researchers used data collected from 2003 to 2004 and 2017 to 2018, and they included almost 20,000 participants, split fairly evenly between men and women. The average age was 52 at baseline (2003-2004).

Participants completed two 24-hour dietary recall questionnaires during those two survey periods, and they were asked to report at what times they ate. From this, researchers calculated an average eating window for each participant. Based on these times, they were categorized into one of the following eating windows: less than eight, eight to 10, 10 to 12, 12 to 14, 14 to 16 and more than 16 hours. 

As part of the surveys, participants provided demographics, health histories and medical diagnoses. Researchers used the National Death Index to track participants’ deaths and causes of death. 

What Did This Study Find?

After running several statistical analyses, including ones adjusting for certain demographics, like sex, age, BMI and lifestyle behaviors, researchers found that, compared to a 12- to 14-hour eating window, restricting the eating window to less than eight hours each day was associated with a 135% increase in the risk of dying from heart disease. This association remained strong in both the overall sample, which included all participants, as well as samples of people with heart disease or diabetes. 

Researchers found no association between intermittent fasting and cancer mortality or overall mortality, though one model did show a 40% increase in overall mortality risk for the eating window of less than eight hours. 

Some limitations of this study include the risk of bias and inaccuracies in participants’ reporting of what they ate. Plus, researchers drew data from just two 24-hour food recalls for each participant, which may or may not be representative of their regular eating habits. Researchers were also not able to determine where in the 24 hours the eight-hour eating windows fell—early in the day or later. That timing may affect the health consequences of intermittent fasting.

How Does This Apply to Real Life?

Though not all studies suggest a negative association between intermittent fasting and health, results like these do trigger a pause. While more research needs to be done, if you engage in intermittent fasting, it might be worth asking yourself what benefits you’re gaining from it and how you might gain the same benefits using a different, less restrictive strategy. 

At EatingWell, we encourage you to tailor your eating habits to your lifestyle and preferences. But we also know that the body works best when it gets the energy and nutrients it needs throughout the day. After all, your body doesn’t take a break from using energy and burning calories, even while you’re sleeping. 

Regarding weight loss, there is evidence suggesting that intermittent fasting is no more effective than simply reducing calories. If weight loss is a goal of yours, there are other ways to go about it that will keep you energized and nourished throughout your day. And yes, we have a meal plan for that! We suggest our 7-Day No-Sugar Mediterranean Diet Meal Plan for Weight Loss to get you started. When you’re ready for more, dive into our 30-Day High-Protein, High-Fiber Meal Plan for Weight Loss. (And then start trying out more of our favorite, flavorful recipes for weight loss, like these tasty snacks.)

Of course, food isn’t the only way to a healthy weight—or heart. Physical activity is also key, as is addressing your stressors and getting enough quality sleep. Choose which areas you want to start with and develop a plan that includes your goals and the obstacles you might face along the way. Just remember that the best strategy for your health should be adaptable and allow you to be kind to yourself. A weight loss journey can be tough, but planning and setting realistic goals can be a big help.

Our Expert Take

This study suggests that people who engage in intermittent fasting with an eating window of less than eight hours may have a 135% increased risk of dying from heart disease compared to people who allow for a 12- to 14-hour eating window. If you love your intermittent fasting and feel you’re getting real benefits from it, just be aware of the potential longer-term risks to your health. If you desire to lose weight but know intermittent fasting isn’t for you, consider following any of our meal plans for weight loss or talking with a registered dietitian who can help you tailor strategies to your preferences and lifestyle.