Time-restricted eating, a common weight-loss strategy often known as intermittent fasting, has been linked to a significantly higher risk of cardiovascular death.

In a study published by the American Heart Association (AHA), a group of 20,000 adults who followed an eight-hour time-restricted eating schedule were found to have a 91% higher risk of dying from heart disease compared to those who spread out their meals across 12 to 16 hours.

The findings were presented at the American Heart Association’s Epidemiology and Prevention│Lifestyle and Cardiometabolic Scientific Sessions last week in Chicago, although the study has not yet been peer-reviewed.

Here are more details. 

What is time-restricted eating?

There are several types of intermittent fasting — but they all follow the same concept of alternating between fasting and eating. 

With a time-restricted approach, the dieter only eats during a certain window. 

For example, with the 16/8 method, the person fasts for 16 hours and then can eat within an eight-hour span, between 10 a.m. and 6 p.m. 

Other versions involve fasting for a full 24 hours once or twice per week — or only consuming limited calories on fasting days.

Previous studies have found that time-restricted eating can improve key measures related to heart health, including blood pressure, blood glucose and cholesterol levels, the AHA noted in a press release.

“Restricting daily eating time to a short period, such as eight hours per day, has gained popularity in recent years as a way to lose weight and improve heart health,” said senior study author Victor Wenze Zhong, PhD, a professor and chair of the department of epidemiology and biostatistics at the Shanghai Jiao Tong University School of Medicine in Shanghai, China, in the release. 

“However, the long-term health effects of time-restricted eating, including the risk of death from any cause or cardiovascular disease, are unknown.”

What are the study details?

Researchers from the Shanghai Jiao Tong University School of Medicine in Shanghai, China, analyzed information from the annual 2003-2018 National Health and Nutrition Examination Surveys (NHANES).

They compared it to causes of death logged by the Centers for Disease Control and Prevention (CDC) between 2003 and December 2019.

People who ate all daily food in a window of less than eight hours had the highest (91%) risk of cardiovascular death, followed by those who ate in a window of between eight and 10 hours (a 66% risk).

The higher risk of heart-related deaths was also seen in those who had existing heart disease or cancer, the release stated.

“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 to 16 hours per day, a shorter eating duration was not associated with living longer,” Zhong said in the release.

Researchers followed the participants for an average of eight years, with some followed for as long as 17 years.

The average age of the participants was 49. 

Researchers followed them for an average of eight years, with some followed for as long as 17 years.

What are the study’s limitations?

Dr. Lou Vadlamani — a cardiologist and founder of VitalSolution, an Ohio-based company that offers cardiovascular and anesthesiology services to hospitals nationwide — was not involved in the study but offered his insights on the findings.

“As with all studies, the devil is in the details,” he said. “While this study provides some fuel for discussion and encourages further studies, it is far from conclusive.”

The fasting habits were based on just two days of recorded eating habits, Vadlamani noted — and it hinged on the recollections of the participants.

“There was no documentation of what the participants ate while they weren’t fasting or what their activity levels were,” he noted.

The timing of the fasting — whether it was daytime or nighttime — was also not clear.

“To conclusively say with any confidence that fasting has a direct impact in rates of heart attack would be a stretch,” the cardiologist said.

“It certainly raises a lot of questions and supports the need for a more comprehensive study, since intermittent fasting has become so common.”

Registered dietitian Lauren Harris-Pincus, author of “The Everything Easy Pre-Diabetes Cookbook,” cautioned that this research has not yet been fully published and peer-reviewed — which means a complete analysis of its findings is “premature.”

“There seems to be an important change between the short-term benefits of the time-restricted diet and the long-term risks.”

She was also not involved in the study.

“While this may suggest a correlation between intermittent fasting and death from cardiovascular disease, that does not prove causation,” the New Jersey-based expert told Fox News Digital.

“There seems to be an important distinction between the short-term benefits of the time-restricted diet and the long-term risks.”

She added, “The conclusions counteract the positive benefits of time-restricted eating in a body of previous research, plus the data was based on self-reported dietary records at a few points in time.”

It’s not known whether the participants continued time-restricted eating for the duration of the study period, Harris-Pincus pointed out. And self-reported food intake can be affected by memory lapses or unintentional inaccuracies. 

“It also did not evaluate additional lifestyle factors that play a role in overall health,” she said.

Anyone with medical conditions should speak to their physician or registered dietitian before starting any restrictive diet, Harris-Pincus recommended. 

She added, “Intermittent fasting is not appropriate for people with a history of disordered eating or active eating disorder, those with hypoglycemia or Type 1 diabetes on insulin, children under 18, pregnant or breastfeeding women, and more.” 

Despite the limitations, Tanya Freirich, a registered dietitian nutritionist in North Carolina who works as The Lupus Dietitian, said the study is a “very important addition” to the current data on time-restricted eating. 

“Additionally, while we don’t learn the details of the participants’ diet in the study, what you eat is incredibly important as well.”

“In the past, there have been many benefits noted with time-restricted eating; however, this study is perfect proof that more is not always better,” Freirich, who was not involved in the study, told Fox News Digital. 

“There seems to be an important distinction between the short-term benefits of the time-restricted diet and the long-term risks.”

The study reinforces the importance of receiving personalized nutrition advice, according to Freirich.

“For people on certain medications or for people who have difficulty maintaining stable blood sugar, blood pressure, or hydration, time-restricted eating may be too difficult to maintain and detrimental to their health,” she cautioned.

“Additionally, while we don’t learn the details of the participants’ diet in the study, what you eat is incredibly important as well.”

In light of this new research available, Freirich advised that people following a time-restricted eating pattern check in with their doctor and assess their cardiovascular health.  

Fox News Digital reached out to the American Heart Association and the study researchers for additional comments.

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