Intermittent fasting, a diet pattern involving alternating patterns of fasting and eating, has gained popularity worldwide as a good way to lose weight, lower blood pressure and improve heart health. However, a recent study shows the possible link between intermittent fasting and the risk of cardiovascular disease in the long term. Intermittent fasting for short periods of up to 3 months may have benefits but not for longer periods, say experts.
Intermittent fasting and heart: What the study says?
The preliminary research presented at the American Heart Association’s Epidemiology and Prevention Lifestyle and Cardiometabolic Scientific Sessions 2024, held in March 18- 21, 2024, in Chicago, US analyzed over 20000 American adults. The cohort were on an 8 hour time-restricted eating schedule which is a type of intermittent fasting. “They had a 91% higher risk of dying from cardiovascular disease,” the study findings revealed. The researchers added that the people with heart disease or cancer also had an increased risk of cardiovascular death. “Compared with a standard schedule of eating across 12-16 hours per day, limiting food intake to less than 8 hours per day was not associated with living longer,” the study said.
However, the research has not yet been published in an academic journal and is yet to be peer-reviewed.
What is intermittent fasting?
Intermittent fasting involves a time-restricted eating pattern, where people limit the eating hours, that usually range from 4-12 hours, and indulge in fasting for the rest of the day. There are several types of intermittent fasting, however the most prevalent and widely used is time-restricted fasting, where people fast for 16 hours and have an 8-hour eating window.
Dr Zeenath Begum, clinical cardiologist, Prashanth Hospitals, Chennai, says “Any fasting should be followed under a doctor’s guidance. One must screen beforehand for any morbidity conditions such as hypertension, diabetes and gallstone”.
Researchers investigated the possible long-term health effects of adopting an 8-hour time-restricted eating regimen. They compared dietary patterns among participants in the annual 2003-2018 National Health and Nutrition Examination Surveys (NHANES) to data from the Centres for Disease Control and Prevention’s National Death Index database, which covered the period from 2003 to December 2019.
Dr Rahul Chandola, founder-chairman and chief of cardiothoracic surgery, Institute of Heart Lungs Diseases Research Centre (IHLD), Delhi, says that the cohort in the study would eat during the 4-8 hours of eating window, and do not consume any calorie for the rest of the day. “The number of calories consumed during their eating window is not clear. However, what you consume and how many calories you consume is more important than timing it,” said Dr Chandola.
Limitations of the study
One of the study’s limitations was that it relied solely on participant-reported dietary data, which could be influenced by memory or recollection and might not be an accurate representation of regular 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.
Dr Chandola adds that the latest study is a non-randomized control, but for anything to prove or disprove, we need a randomized study, wherein, one group of subjects would consume a restricted hour diet and another group, consumes, a 24-hour diet or maybe more than 16-hour diet. “Time-restricted eating is only good if whatever you eat is healthy”, says Dr Chandola.
Agreeing with Dr Chandola, Dr Ranjan Shetty, HOD and consultant interventional cardiology, Manipal Hospital, Old Airport road, Bangalore highlighted the lack of baseline comparison such as both groups consisting of an equal number of subjects having conditions such as diabetes or hypertension, division of gender and age as well as the risk factors of these subjects to compare.
Dr Shetty said that intermittent fasting has gained popularity only now where those who are healthy are also picking it up. “But the study goes way back in 2003 when people opted for intermittent fasting only when they had specific health conditions. We do not know the reason behind the subjects choosing intermittent fasting and if they had the risk factors of heart diseases,” he says, pointing out the lack of information on subjects in the study.
Prolonged time restricted eating pattern linked to cardiac issues?
Dr Begum says, during fasting, the cortisol level increases. “This in turn increases the blood pressure and the heart rate which can lead to any cardiovascular disease in the long term,” she said.
She explains, when a person fasts for 14 -16 hours, the remaining hours, in the one must take a balanced diet. An unhealthy diet in the 8 hour eating window, increases the LDL(bad cholesterol), which gets deposited in the artery and can cause cardiovascular disease. “High LDL deposition in the artery, can lead to development of atherosclerosis (thickening of the arteries) and coronary artery disease,” Dr Begum said.
Dr Begum points out that the latest study is limited to the US population, and not global. The “US population and their eating habits are completely different as they may consume processed and frozen food in their diet.”
She recommends fasting for 12 or 14 hours and consuming a balanced diet for the rest of the day, along with proper hydration. She cautions against indulging in unhygienic food habits while fasting. She also advises against following intermittent fasting for a longer period. “It can be followed for 2-3 months in a year”, she adds.
Dr Chandola advises adopting a heart healthy diet which is low calorie, low fat and high in antioxidants and proteins. This diet is required to have minimal cardiovascular risk, thereby also leading to less risk of dying of any cardiovascular disease.
Takeaways
A recent study indicates 91% higher risk of cardiovascular death due to intermittent fasting. With the study having multiple limitations, experts stress the need for more randomized studies to establish the link between intermittent fasting and cardiovascular deaths. However, experts say that intermittent fasting for short periods up to 3 months may have benefits including heart health and caution against long-term practice of intermittent fasting.
