Intermittent fasting may radically increase the risk of death due to cardiovascular disease, according to a new study.
The study by researchers from Shanghai Jiao Tong University School of Medicine in China looked at intermittent fasting, a popular diet pattern that limits eating to a specific number of hours each day, which may range from a 4- to 12-hour time window in 24 hours.
Past research has suggested such eating patterns can help people lose weight and lower their blood pressure, but this study found people who followed a pattern of eating all their food across less than eight hours per day had a 91% higher risk of dying from cardiovascular disease over an eight-year period, compared to people who ate across 12 to 16 hours.
Analysis presented at the American Heart Association’s (AHA) scientific sessions in Chicago on Monday – which has not yet been peer-reviewed or published in an academic journal – is based on data from the Centres for Disease Control and Prevention’s National Health and Nutrition Examination Survey collected between 2003 and 2018.
The researchers analysed responses from around 20,000 adults who recorded what they ate for at least two days, then looked at who had died from cardiovascular disease after a follow-up period of eight years.
The analysis also found there was an increased risk of cardiovascular death seen in people living with heart disease or cancer, and that among people with existing cardiovascular disease, an eating duration between 8-10 hours per day was associated with a 66% higher risk of death from heart disease or stroke.
Researchers added their analysis suggested time-restricted eating “did not reduce the overall risk of death from any cause” and that having an eating duration of more than 16 hours per day was associated with a lower risk of cancer mortality among people with cancer.
Victor Wenze Zhong, the study’s senior author, said the findings were “surprising”, adding: “We had expected that long-term adoption of eight-hour time-restricted eating would be associated with lower risk of cardiovascular death and even all-cause death.
“We were surprised to find that people who followed an eight-hour, time-restricted eating schedule were more likely to die from cardiovascular disease. 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.
“It’s crucial for patients, particularly those with existing heart conditions or cancer, to be aware of the association between an eight-hour eating window and increased risk of cardiovascular death.
“Our study’s findings encourage a more cautious, personalised approach to dietary recommendations, ensuring that they are aligned with an individual’s health status and the latest scientific evidence.”
More research needed, study leaders admit
The study, its researchers admit, has limitations, including its reliance on self-reported dietary information, which they say “may be affected by participant’s memory or recall and may not accurately assess typical eating patterns”.
“Factors that may also play a role in health, outside of daily duration of eating and cause of death, were not included in the analysis,” they add.
Dr Zhong added it was too early to make specific recommendations about intermittent fasting based on his research alone but people should be “extremely cautious” about long-term fasting patterns.
He said it was not clear why his research found an association between time-restricted eating and a risk of death from cardiovascular disease.
He did theorise that people who limited their eating to fewer than eight hours per day may have less lean muscle mass than those who ate for 12 to 16 hours. Low lean muscle mass has been linked to a higher risk of cardiovascular death.
Dr Pam Taub, a cardiologist at UC San Diego Health, told Sky News’ US partner NBC News: “It’s a retrospective study looking at two days’ worth of data, and drawing some very big conclusions from a very limited snapshot into a person’s lifestyle habits.”
She added her patients have seen “incredible benefits” from fasting regimens, before concluding: “I would continue doing it. For people that do intermittent fasting, their individual results speak for themselves.
“Most people that do intermittent fasting, the reason they continue it is they see a decrease in their weight. They see a decrease in blood pressure. They see an improvement in their LDL cholesterol.”