Intermittent Fasting Linked to Significantly Higher Risk of Death from Heart Disease (2024)

Intermittent fasting devotees who follow a strict 8-hour eating window and fast for the other 16 hours in the day may be at a 91% increased risk of death from cardiovascular disease, preliminary research from a new study says.

The study analyzed 20,000 adults in the U.S., and according to a press release, found that “people who limited their eating across less than 8 hours per day as part of the time-restricted eating plan intermittent fasting, were more likely to die from cardiovascular disease compared to people who ate across 12-16 hours per day.”

Proponents of intermittent fasting like the ease of the system, which limits eating hours to a portion of the day, then requires "fasting" during the remaining hours to lose weight. Past critics have said that intermittent fasting wasn’t measurably “beneficial” to weight loss compared to the traditional calorie-counting method, where a person simply eats fewer calories than they burn in a day.

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And last June, another study showed that calorie counting and intermittent fasting are equally effective when it comes to weight loss — as people were essentially consuming the same amount of calories they would normally consume in a calorie-restricted day, just in a shorter window.

People who practice intermittent fasting can follow different patterns for eating, fasting for alternating days or for several hours every day, Verywell Health reports.

This new study — which was presented at the American Heart Association’s Epidemiology and Prevention│Lifestyle and Cardiometabolic Scientific Sessions 2024, a conference currently taking place in Chicago — specifically looked at the health risks of those who followed the 16:8 method, which is fasting for 16 hours and eating for 8 hours and considered one of the more popular methods of IF.

“We were surprised to find that people who followed an 8-hour, time-restricted eating schedule were more likely to die from cardiovascular disease,” said senior study author Victor Wenze Zhong, Ph.D., a professor and chair of the department of epidemiology and biostatistics at the Shanghai Jiao Tong University School of Medicine in Shanghai, China.

“Even though this type of diet has been popular due to its potential short-term benefits, our research clearly shows that, compared with a typical eating time range of 12-16 hours per day, a shorter eating duration was not associated with living longer,” Zhong said.

Others noted that the full study hasn’t been released yet — and the type of food the participants were eating is a crucial piece.

“One of those details involves the nutrient quality of the diets typical of the different subsets of participants. Without this information, it cannot be determined if nutrient density might be an alternate explanation to the findings that currently focus on the window of time for eating,” said Christopher D. Gardner, Ph.D., FAHA, the Rehnborg Farquhar Professor of Medicine at Stanford University in Stanford, California.

“Second, it needs to be emphasized that categorization into the different windows of time-restricted eating was determined on the basis of just two days of dietary intake,” he continued.

Gardner is co-author of American Heart Association’s Popular Dietary Patterns: Alignment with American Heart Association 2021 Dietary Guidance, which addressed how well popular diets like Keto and Paleo align with a heart-healthy diet. (They “align poorly” as “overconsuming fatty meats and sodium may be detrimental to health.”)

The best diets, according to the guidelines, are Mediterranean, which is high in unprocessed foods and focuses on lean fish, legumes and vegetables, and DASH-Style, a Dietary Approach to Stop Hypertension that is similar to Mediterranean.

Pescetarian, and ovo/lacto-vegetarian diets — avoiding meat entirely and adding in fish or egg and milk products — were also ranked as heart-healthy.

“The purpose of intermittent fasting is to cut calories, lose weight,” Penny Kris-Etherton, emeritus professor of nutritional sciences at Penn State University and a member of the American Heart Association nutrition committee, told NBC News. “It’s really how intermittent fasting is implemented that’s going to explain a lot of the benefits or adverse associations.”

She added. “Maybe consider a pause in intermittent fasting until we have more information or until the results of the study can be better explained.