According to a 2020 American Journal of Medicine study, intermittent fasting is a popular nutritional or weight loss method, whereby an individual ceases to eat food for anywhere between four and 16 hours in a single day or eats all calories within a specific time window.
Men’s Health UK reported in 2019 that famous celebrities and fitness influencers, such as Hugh Jackman and Chris Hemsworth, endorse and practice intermittent fasting. A new research study, however, has highlighted concerning results.
Recent study raises concerns
At conference for The American Heart Association in March 2024, an abstract by researchers at Shanghai Jiao Tong University concluded that individuals who eat all meals across eight hours per day have a 91 per cent higher risk of heart-related death.
Dr. Victor Wenze Zhong and his research team told the conference that the so-called 16:8-hour periods of time-restricted eating are most common. These involve fasting for 16 hours but eating all meals in an eight-hour period.
The study reviews a sample of 20,000 U.S. adults, and each participant self-reports data on dietary plans. The researchers then compared the participants’ data to the 2019-2024 National Health Index death and diet relationships records to reach their conclusion.
The study concluded that the most popular intermittent fasting time frame is linked to a 91 per cent higher chance of cardiovascular death. But there are many essential aspects to consider beyond the headline.
Dr. Zhong and his colleagues do acknowledge in their methods that intermittent fasting is reportedly beneficial in short-term analysis, and the study suffers from potentially unreliable self-reported dietary information.
Mount Royal University performance dietitian, Erin Krill, says there is little evidence in support of intermittent fasting for long-term weight loss, and she has witnessed an increase in cravings with people who intermittently fast.
“In my work with athletes, time restricted eating is also discouraged as it can lead to fasted workouts which puts the body at higher risk of injuries,” says Krill.
The Shanghai researchers also acknowledge that time-restricted eating does not directly cause cardiovascular death (para. 23), and additional factors outside of daily dietary regimens are not included in the analysis.
Additionally, Dr. Zhong and his colleagues discovered a medical trend from data that has yet to be replicated or peer-reviewed. The data available is new and it may be a while until peer-reviewed research verifies these conclusions.
Similar research also raises concerns
A 2020 study by a Canadian family physician involved a drastically smaller sample size of more than 900 participants. Still, 27 variant intermittent fasting trials ranging from two weeks to 12 weeks recorded no adverse results . However, the same research team found that more long-term studies are needed to expand our current knowledge of the intermittent effects of fasting over longer time periods.
Muslim university student Zaieem Ishtiaq practices intermittent fasting during Ramadan, a cultural celebration that involves refraining from eating for a month every year. Much like the 16:8 method, Ishtiaq says he fasts from dawn to sunset and then eats a meal before sunrise and after sunset.
“Fasting is difficult for the month that I do it. But I have been a part of Ramadan for six years, and I have never experienced any adverse effects,” says Ishtiaq.
Another 2020 study, by the American Journal of Medicine, suggests three ways intermittent fasting can benefit the body, including circadian rhythm theory (para. 5), which links specific timed intermittent fasting to organ optimization and cardiovascular benefits.
However, similar to those findings by the Canadian family physician, researchers with the American Journal of Medicine note that no controlled large-scale randomized trials (para. 1) on intermittent fasting existed at the time of the study.
And a 2019 study conducted by researchers at Nutrients claims that intermittent fasting actually limits several risks of cardiovascular disease by undergoing energy processes, but they wave a red flag at multiple disadvantages with intermittent fasting unrelated to cardiovascular death.
The Canadian Journal of Cardiology also suggested long-duration intermittent fasting trials are needed (conclusions and future remarks) for proper examination.
Other research articles consulted contain similar statements on the future of intermittent fasting research, and current data is overwhelmingly done over short-term periods.
More research is needed
Researchers have discovered multiple positive effects of intermittent fasting in controlled, short-term studies. However, no current research or peer-reviewed studies exist to prove or disprove Dr. Zhong’s claims. More research is needed to support any conclusive evidence.