Study linking intermittent fasting to higher risk of heart disease death questioned by researchers: ‘No clear answers’
- A study of 20,000 adults found the risk of dying from cardiovascular disease almost doubled for those following a 16:8 eating plan
- But health experts have said the findings did not take into account pre-existing medical issues and more research is needed
But experts are holding off on making any strong calls over the time-restricted eating plan, pointing out flaws in the findings and saying more research is needed.
The findings were presented at an American Heart Association (AHA) conference in Chicago held from March 18 to 21, with a paper set to be published soon in a peer-reviewed journal, according to a statement from the AHA on March 19.
“However, the long-term health effects of time-restricted eating, including the risk of death from any cause or cardiovascular disease, are unknown,” he added.
This was the eating plan which the study looked at, analysing its potential long-term health effects, based mainly on information taken from the US National Health and Nutrition Examination Survey (NHANES) database between 2003 and 2018.
Nearly 20,000 adult participants were asked to complete two dietary questionnaires within the first year of enrolment, and during a median follow-up of eight years (with a maximum of 17 years), 2,797 deaths were recorded, of which 840 were from cardiovascular causes.
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“Overall, this study suggests that time-restricted eating may have short-term benefits but long-term adverse effects,” Christopher Gardner, a professor of medicine at Stanford University who was not involved in the research, said in the AHA statement.
But both nutrition and cardiology experts have voiced reservations over the findings, saying more comprehensive research is needed before a definitive link can be made between time-restricted diets and the risk of cardiovascular disease.
Dr Kenneth Mukamal, a primary care doctor at Beth Israel Deaconess Medical Centre and a professor of medicine at Harvard Medical School who was not involved in the study, told AHA News on March 18 that many factors remain unaccounted for.
Focusing on what people eat is more important than focusing on the time in which they eat
He noted that it was an observational study, not a randomised trial, and added that it is important to find out why people choose to eat this way. Those with cancer, for example, may be struggling with loss of appetite.
“At least as of now, focusing on what people eat is more important than focusing on the time in which they eat,” Mukamal said.
Zhang Peng, a doctor at Beijing Friendship Hospital at Capital Medical University, said the conclusions of this study would not change his hospital’s clinical practice.
“Many studies in nutriology often come to controversial conclusions under different conditions,” he said, “and there are no particularly clear answers about intermittent fasting either, although overall there is more evidence that the benefits outweigh the drawbacks.”
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He said the study presented at the conference was “not surprising at all” because it did not provide more detailed information about the participants, such as whether they had underlying medical conditions including type 2 diabetes or cardiovascular disease.
As a doctor in bariatrics and metabolic surgery, Zhang said patients are treated on a categorical and precise basis. For those who are simply obese, they would be advised to reduce the time window of eating under calorie control, such as a 16:8 plan.
But this time-restricted eating would not apply to people with some nutritional disorders associated with diabetes, gastrointestinal diseases, cardiovascular disease and other malignancies.
Nutritional management and weight loss are “serious” matters, he said, urging people to consult a health professional rather than make their own decisions simply based on studies.
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Mukamal also said it was too early to conclude that people should avoid time-restricted eating if it helps them achieve their weight-loss goals.
“At this point, if people want to eat over a shorter duration and it’s easier for them to maintain their weight that way, I would not use this as a reason not to do it,” he said.
The authors of the study themselves warned of the limitations of their findings, noting that factors other than daily duration of eating – which could have played a role in cause of death – were not taken into account.
They called for more future research, such as investigating the biological mechanisms underlying the associations between time-restricted eating and adverse cardiovascular outcomes.
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Meanwhile, despite the questions over the voracity of the study, some welcomed its findings, saying that people focus on the short-term benefits of time-restricted eating plans, without fully knowing the long-term effects.
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Instead of intermittent fasting, Tian said calorie restriction is actually more recommended by the academic community.
“Large-scale studies have found that calorie restriction can lead to a number of beneficial changes in health indicators, including longevity,” he said.
It is not the first time a link between intermittent fasting and death from cardiovascular disease has been made.
In a large prospective study involving more than 24,000 adults aged 40 and over, published in the Journal of the Academy of Nutrition and Dietetics in 2022, scientists found that skipping even one meal was associated with an increased risk of all-cause and cardiovascular disease mortality.
