New Delhi: The struggle to lose those stubborn extra kilos brings many, at some point, to the doorstep of intermittent fasting — a dietary approach, also known as time-restricted eating, which limits food consumption to specific hours of the day. While many who opt for it see it as a potent weight-loss tool, whether it is safe for overall health and well-being in the long run, has been a matter of debate.
According to findings from new research presented at the American Heart Association’s Epidemiology and Prevention | Lifestyle and Cardiometabolic Scientific Sessions 2024 released on 19 March, those who followed an 8-hour time-restricted eating schedule — a popular type of intermittent fasting — had a 91 percent higher risk of death from cardiovascular disease.
Time-restricted eating — a kind of intermittent fasting — involves limiting the eating hours to a specific number each day, which may vary from a 4- to 12-hour window in 24 hours.
The study, which is yet to be published in a peer-reviewed scientific journal, included nearly 20,000 adults in the US with an average age of 49 years who were followed for a median length of eight years and a maximum length of 17 years.
Compared with a standard eating schedule across 12-16 hours a day, limiting food intake to less than 8 hours was not associated with living longer, the researchers found.
These results have grabbed headlines and triggered further debates on whether the health fad deserves the prominence it gets.
However, most health experts ThePrint spoke to underlined that, while the latest observations are unique, they also emphasised that more evidence was needed to assess its long-term impact on a person’s overall health.
For instance, Dr Pradeep Haranahalli, consultant, interventional cardiologist, with Manipal Hospital, Bengaluru, suggested that, while the new results have shaken the understanding around intermittent fasting for some, it is too early to draw such conclusions based on an abstract of a study that is not yet peer-reviewed or published.
Also, the study had several limitations, like data collection was based on self-reporting of diet information by patients, which is subject to memory recall bias, he highlighted.
Haranhalli told ThePrint that the study does not explain the biological mechanisms that establish an association between time-restricted eating and adverse cardiovascular outcomes. “However, following the fad may be looked at as a word of caution for those who already have cardiovascular disease against practising it,” he cautioned.
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Does intermittent fasting work?
While fasting for religious reasons has been practised across cultures for centuries, the alternating cycles between voluntary fasting and non-fasting as a weight-loss method have become popular over the past few decades.
Experts agree that while asking someone to restrict what they eat can be difficult when applied to every meal, every time — intermittent fasting comes as a convenient shortcut of sorts, where the person can enjoy a normal diet when not fasting.
Some of the common types of intermittent fasting include restricting all eating to a 6 to 8-hour window each day, regularly eating five days of the week and only eating one meal on the remaining days or alternating days of regular eating with days when a person consumes less than the specified number of calories.
The rise of intermittent fasting as a fad can be attributed to various factors, including its association with celebrities, social media influence, and the appeal of a simplified approach to weight management, pointed out Seema Gulati, head of the nutrition research group at Delhi-based non-profit National Diabetes, Obesity, and Cholesterol Foundation.
According to Dr Rajeev Jayadevdan, a gastroenterologist and medical researcher from Kerala, in the short term, intermittent fasting is not known to cause any serious adverse effects apart from headaches, mood disturbances, constipation and binge eating.
In fact, studies in small animals have shown that it is beneficial in the long term, however, a 28-year study on monkeys failed to demonstrate benefit, he highlighted.
However, Jayadevan opined that the long-term effects of intermittent fasting in humans will only be known as we go forward. “Studies like the one that has come out now are the way forward. But we must wait for the full peer-reviewed publication before jumping to conclusions,” he added.
For Dr Nagaraj Palankar, consultant of surgical gastroenterology with Manipal Hospital in Bengaluru, too, the benefits and harms of intermittent fasting are unclear, with some studies showing benefits but others contradicting it.
“Nutritional epidemiology, a field of science that involves the study of the role of nutrition in diseases, suffers from a lack of high-quality experimental studies,” he said.
For instance, he added, a high-quality study conducted in China had shown that patients who practised time-restricted eating did not have any benefit over patients who ate ad libitum — as often and as much as desired — but at the same time maintained caloric restriction and consumed a balanced diet with adequate protein consumption.
“In my view, it is important to eat a balanced diet with adequate proteins, preferably with slight caloric restriction; whether one wants to eat in a narrow window or ad libitum should be left to them rather than being dogmatic that one approach is better than the other,” said Palankar.
Jayadevan maintained that anecdotally, people say they lose weight when on time-restricted diets, but that’s expected when one cuts down the amount of calories they consume, particularly when they avoid a heavy supper.
However, small observational studies are prone to various types of bias that affect their conclusions, he stressed, adding that “the real metabolic benefits will only be apparent when large numbers of people are systematically studied.”
While intermittent fasting can offer potential benefits, such as weight loss and improved metabolic health for some individuals, it’s crucial to recognise that it may not be suitable for everyone, Gulati highlighted. “The effects can vary based on factors, such as individual health status, age, and lifestyle.”
(Edited by Richa Mishra)
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