Intermittent fasting is being touted for a range of short-term benefits revealed in recent studies, but we don’t know much about its long-term effects. A new study has found some concerning links that may outweigh the benefits of intermittent fasting in the long run.
One form of this popular dietary intervention, known as time-restricted eating (TRE), has dieters restricting their food intake to within a window of just eight hours or less in a day, and fasting for the remaining 16 hours or more.
While some people undertake this extreme form of dieting under medical supervision to address specific health issues, many are taking it upon themselves as a way to fast-track weight loss, without medical advice.
Perhaps not surprising, with celebrities like Jennifer Aniston, Hugh Jackman, Halle Berry, Chris Hemsworth, and Kourtney Kardashian promoting the practice as a way of controlling physique.
While weight is one aspect of a healthy body, the new research by a team in China suggests that TRE is linked to some serious and concerning long-term effects, including cardiovascular disease and early death.
“We found that people who followed eight hour TRE had higher cardiovascular mortality, both in the general population and in people who have cancer and cardiovascular disease as a baseline,” says epidemiologist Victor Zhong, from Shanghai Jiao Tong University.
And while research has found some cardiovascular benefits, Zhong is concerned that most of these studies are conducted over less than a year, missing the bigger picture.
“Based on what we know so far, focusing on what people eat may be more important than focusing on when they eat,” he says. “There are many healthy dietary choices… that we can choose to lower cardiovascular death risk.”
The observational study was based on data from over 20,000 US adults who participated in the country’s National Health and Nutrition Examination Survey in 2003-2018, with participants’ mortality status as of December 2019 obtained from the CDC’s National Death Index.
The analysis revealed people who restricted their day’s eating to a window of eight hours or less had a 91 percent higher risk of death due to cardiovascular disease. This was also the case among people with heart disease or cancer.
For people with existing cardiovascular disease, restricting their eating window between 8 and 10 hours a day was associated with a 66 percent higher risk of death from heart disease or stroke.
The study also found TRE had no effect in reducing the risk of an early death, from any cause.
For people with cancer, eating over a period of 16 hours or more during the day was actually linked to a reduction in the risk of dying of cancer.
At this stage, these are only links, not causes: “Although the study identified an association between an 8-hour eating window and cardiovascular death, this does not mean that time-restricted eating caused cardiovascular death,” Zhong explains.
The team did find people who followed TRE had a lower lean muscle mass than others, which has been linked to cardiovascular mortality, Zhong says, but further research is needed to properly understand these mechanisms.
“It’s crucial for patients, particularly those with existing heart conditions or cancer, to be aware of the association between an 8-hour eating window and increased risk of cardiovascular death,” Zhong says.
“Our study’s findings encourage a more cautious, personalized approach to dietary recommendations, ensuring that they are aligned with an individual’s health status and the latest scientific evidence.”
This research was presented at the American Heart Association’s EPI|Lifestyle Scientific Sessions 2024.
