A popular intermittent fasting method, which celebrities and influencers have promoted, has been linked to an increased risk of cardiovascular death.
According to preliminary findings presented at an American Heart Association meeting, adults who followed an eight-hour time-restricted eating schedule had a 91 per cent higher risk of death from cardiovascular disease.
Here's what you need to know.
What is intermittent fasting?
Intermittent fasting is a type of eating plan structured around time restriction.
There are different formats of intermittent fasting, but all involve having regular periods to eat and fast.
Some follow the one meal-a-day approach, which - as the name suggests - involves fasting for 23 hours and then consuming your daily intake of calories in a one-hour period.
The 16:8 fasting method involves fasting for 16 hours and only eating during an eight-hour window.
For example, somebody following this method might only eat between 10am and 6pm, and fast for the rest of the day.
Previous research has found that time-restricted eating improves several cardiometabolic health measures, such as blood pressure, blood glucose, and cholesterol levels.
What are the risks of intermittent fasting?
In the new study, which is yet to be peer-reviewed, researchers investigated the potential long-term health impacts of having an eating window of less than eight hours.
The researchers analysed 20,000 US adults, and participants were followed for a median length of eight years and a maximum length of 17 years.
The study found those who ate all of their food across less than eight hours per day had a 91 per cent higher risk of death due to cardiovascular disease.
Among those with existing cardiovascular disease, an eating duration between eight and 10 hours per day was also associated with a 66 per cent higher risk of death from heart disease or stroke.
Time-restricted eating did not appear to reduce the risk of death from any cause.
"We were surprised to find that people who followed an eight-hour, time-restricted eating schedule were more likely to die from cardiovascular disease," study author Victor Wenze Zhong said.
"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."
Which celebrities have promoted intermittent fasting?
Friends star Jennifer Aniston is just one celebrity who's expressed their love for intermittent fasting, particularly the 16:8 diet.
The 55-year-old revealed in 2019 that she skips breakfast and only consumes liquids, like celery juice or coffee, in the morning.
"I noticed a big difference in going without solid food for 16 hours," she told the Radio Times in 2019. "
Other famous faces who've tried intermittent fasting methods, whether as an ongoing practice or in the short term, include Hugh Jackman, Chris Hemsworth, Kourtney Kardashian, Halle Berry, Chris Martin, and Heidi Klum.
Jennifer Aniston is a fan of intermittent fasting. Source: AAP / Allison Dinner/EPA
What do experts say about the new findings?
The study's authors acknowledged the limitations of their research, namely its reliance on self-reported dietary information, which they said could be affected by participants' memories and may not accurately assess their typical eating patterns.
Other factors that could play a role in a person's health, outside of the hours they eat each day and their cause of death, weren't included in the analysis, they added.
"Overall, this study suggests that time-restricted eating may have short-term benefits but long-term adverse effects," Christopher Gardner, the director of nutrition studies at Stanford University, said.
Gardner said it would be "interesting and helpful" to learn more about the details of the research once it was presented in full — especially the nutrient quality of the study participants' diets.
"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," he said.
Seeing a comparison of the demographics and baseline characteristics across the different groups would also be "critical", he added.
"For example, was the group with the shortest time-restricted eating window unique compared to people who followed other eating schedules, in terms of weight, stress, traditional cardiometabolic risk factors or other factors associated with adverse cardiovascular outcomes?" he said.
"This additional information will help to better understand the potential independent contribution of the short time-restricted eating pattern reported in this interesting and provocative abstract."
