Intermittent fasting has become the dietary trend of the decade.
He promises to hack biology without the chore of counting the calories or cutting the carbohydrates: simply change when you eat, not necessarily what you eat. The technological magnates swear by it, the Hollywood stars insist to maintain them. Former British Prime Minister Rishi Sunak spoke of starting his week with a 36 -hour fast.
So far, science has seemed favorable. Research suggests that the extension of the fast overnight can improve metabolism, help cell repair and perhaps even prolong life. Nutritionists, however, have long warned that jumping meals is not a miracle solution – and can be risky for people with underlying conditions.
Intermittent fasting is compressed in a short daily window, often eight hours, leaving a 16 -hour gap without food. Other diets restricted in time, such as plan 5: 2, limit calories on certain days rather than hours.
Now, the first large -scale study of this type raises a more serious red flag. The researchers, analyzing data of more than 19,000 adults, found that those who confined their diet for less than eight hours a day were faced with a risk of 135% higher to die Cardiovascular diseases – Problems with the heart and blood vessels – that people who have eaten more than 12 to 14 hours.
A high cardiovascular risk means that, depending on the health, lifestyle and medical data of a person, it is more likely than others of the study to develop heart problems such as the heart attack or stroke.
The link with overall mortality – the deaths of any cause – was lower and inconsistent, but the cardiovascular risk persisted through age, sex and lifestyle groups even after rigorous tests.
In other words, the study has found only a weak and inconsistent link between the restricted food in time and global deaths. But the risk of dying of cardiovascular diseases was strongly higher.
The authors emphasize that the study does not prove the cause and the effect. But the signal is sufficiently striking to challenge the story of the fast as a risk -free path towards better health.
The researchers followed American adults over eight years. To understand their eating habits, the participants were questioned over two distinct days – about two weeks apart – to recall everything they ate and drunk. Based on these “food reminders”, scientists estimated that the average food window of each person and treated it as representative of their routine in the long term.
Those who ate in an eight -hour window faced a higher risk of dying by cardiovascular disease than those who propagate meals over 12 to 14 hours, the study revealed.
They found that the high cardiovascular risk was coherent between socio-economic groups, and the strongest among smokers and people with diabetes or existing heart disease, which suggests that they should be particularly cautious about long-term narrow food windows. The link took place even after adjusting the quality of the diet, the frequency of meals and snacks and other lifestyle factors, researchers revealed.
I asked the researchers how we must read the conclusion that the deaths linked to the heart increase so radically, but the global deaths do not do it – is it biology or in the data?
Diet is a main driving force in diabetes and heart disease, and therefore an association with higher cardiovascular mortality is not unexpected, said Victor Wenze Zhong, the main author of the peer study in diabetes and metabolic syndrome: clinical research and magazines.
“The unexpected conclusion is that sticking to a short food window of less than eight hours over the years was linked to an increased risk of death from cardiovascular disease,” said professor Zhong, epidemiologist at the school of medicine at Shanghai Jiao Tong in China.
This goes against popular belief – supported by short -term studies that only last a few months to one year – this restricted diet in time improves heart and metabolic health.
In an editorial who accompanies him in the same review, Anoo Misra, a leading endocrinologist, weighs the promise and the traps of the intermittent fast.
Uplining, he says, several trials and analyzes suggest that it can promote weight loss, improve insulin sensitivity, reduce blood pressure and improve lipid profiles, with proofs of anti-inflammatory services.
It can also help people manage blood sugar without counting of rigid calories, easily adapts to cultural or religious fasting practices and is simple to follow.
“However, the potential drawbacks include nutrient deficiencies, increased cholesterol, excessive hunger, irritability, headache and reduced adhesion over time,” said Professor Misra.
“For people with diabetes, unattended fast risk of dangerous reductions in blood sugar and promotes the consumption of junk food during windows.
This is not the first time that the intermittent fast has faced a meticulous examination.
A rigorous three -month study, published in Jama Internal Medicine in 2020, revealed that the participants have lost only a small amount of weight, a large part of which can come from the muscle. Another study said that intermittent fasting can produce side effects such as weakness, hunger, dehydration, headache and difficulties in concentrating.
The new study, says Professor Misra, now adds a more disturbing warning – a possible link to a higher cardiovascular risk, at least in certain groups.
I asked Professor Zhong what he would advise clinicians and the public to withdraw the last conclusions.
He said that people with heart disease or diabetes should be cautious about the adoption of an eight -hour food window. The results indicate the need for “personalized” food advice, based on health and evolving evidence.
“Based on evidence to date, focus on what people eat seems to be more important than focusing on when they eat. At least people may consider not adopting an eight -hour food window for a long time to prevent cardiovascular disease or to improve longevity.”
Obviously, for the moment, the message is less to completely abandon the fast and adapt it to the risk profile of an individual. Until the evidence is clearer, the safest bet can be less focused on the clock and more on the plate.
