Fasting is a natural method of improving health in body and mind that is as old as the hills of ancient Greece. It has stood the test of time as an extreme form of calorie restriction. It is a vastly different medical, scientific beast from starvation.

In its modern incarnation of intermittent fasting (IF), also known as time-restricted eating or feeding (TRE or TRF), fasting is a global health trend. It involves short, targeted periods of fasting within a 24- to 48-hour cycle. Claimed benefits include treatment and prevention of heart disease, stroke and cancer.

The scientific evidence is mixed. Intermittent fasting faces increasing criticism from scientists and medical doctors due to potentially serious health risks involved in severe calorie restriction.

Now, a new Chinese study that popped up at the American Heart Association (AHA) meeting in Chicago in March muddies the scientific waters. It suggests that far from protecting tickers, intermittent fasting could cause premature death from cardiovascular disease (CVD — heart attack and stroke) in those who indulge in it long term.

According to findings, people who limit their “eating window” to less than eight hours daily had a 91% (almost double) increased risk of dying from heart and circulatory diseases. That’s compared with a more “typical eating window” of 12-16 hours.

It’s likely to strike fear into hearts and minds of the many in SA and globally who have fasted intermittently for years. They should have little fear.

For starters, the study is associational and therefore can’t show causation, as the authors themselves point out. The study is not yet published in a journal. Thus, it has not undergone the rigorous peer review process to support findings.

Johannesburg cardiologist and physician Dr Riaz Motara sees so many problems with the study that he is surprised it made it onto mainstream media radars at all.

The study “smells very fishy”, Motara says. “It was presented as a poster and was not endorsed by the AHA at the meeting,” he says. There were no details of how long patients tried intermittent fasting or what comorbidities they had that might have explained any increased heart risk.

“Crucially, there was no mention of why and how IF could possibly have caused a purported 91% increase in serious risk.”

In a New York Times article, Dr Dariush Mozaffarian, a cardiologist and professor of medicine at Tufts University in the US, calls the study “very problematic”. Other experts call the findings “virtually useless”.

So, why the fuss about intermittent fasting from this study given fasting’s robust history?

The science supporting intermittent fasting is growing, but studies highlight the need for caution due to the risk of eating disorders associated with it.

Fasting, by definition, means voluntarily abstaining from food for a specific period. Compare that with starvation, defined as “extreme suffering or death caused by lack of food”.

Ancient Greek sages, from Hippocrates, the “father of modern medicine”, to Plato, Aristotle and Plutarch, regularly extolled the virtues of fasting as the “physician within”. They considered fasting as an instinct that creates the conditions under which the body can do what it is naturally designed to do: heal itself.

Animals, even when domesticated, always instinctively turn to their “physician within”. They don’t eat when they’re sick.

Intermittent fasting and time-restricted eating therapies are popular globally due to accessibility, flexibility and potential health benefits without continuous calorie restriction from prolonged fasts. The science supporting intermittent fasting is growing, but studies highlight the need for caution due to the risk of eating disorders associated with it.

Intermittent fasting involves different types of calorie restriction and variable fasting times during a 24- to 48-hour cycle. Time-restricted eating is a form of intermittent fasting focusing on eating within limited hours during daylight. It aligns eating patterns with circadian rhythms by consuming meals within eight- to 12-hour daytime windows and fasting during remaining hours.

The aim is to optimise metabolic processes and biomarkers, support physiological functions and improve health outcomes by synchronising eating habits with the body’s “internal clock”.

Popular intermittent fasting approaches include:

  • One meal a day);
  • Alternate-day fasting;
  • Eat-stop-eat: a twice-weekly, 24-hour, calorie-free fast;
  • 5:2: fasting for two days out of every seven by consuming only 500-600 calories on those days; and
  • 16/8: also known as the Leangains diet, involves fasting for 16 hours and eating within an eight-hour time frame.

Animal and human research supports intermittent fasting with improvements in metabolic disorders, such as obesity, type 2 diabetes, liver problems and neurological diseases.

Calorie restriction
Calorie restriction

The authors of a multi-centre US and South American review of the literature in 2023 suggest a “crucial explanation” by which intermittent fasting and time-restricted eating can work their healthy magic. These “permit a set time length for caloric ingestion, during which our systems activate a variety of mechanisms that lead to the enhancement and renewal of different body systems”.

Motara stresses the importance of health benefits of calorie restriction. “Whether you are intermittent fasting or not, high-density, micronutrient-deficient foods will increase your risk [of cardiovascular disease],” he says.

He supports the adage about eating “breakfast like a king, lunch like a prince and supper like a pauper”.

Populations that normally have significant calorie restriction in poor communities do not show an increased cardiovascular risk, Motara says. “They are more likely to succumb to the effects of severe malnutrition.”

The bigger problem is “the ready availability of cheap, high-carbohydrate, high Omega-6 and micronutrient-deficient foods”, he says.

That refers to the “obesogenic environment”, a term coined by New Zealand researcher Dr Boyd Swinburn. It refers to the sum of influences in our surroundings that promote obesity in individuals or populations. It encompasses availability, accessibility and affordability of energy-dense (junk and fast) foods, marketing strategies promoting unhealthy eating and other environmental conditions contributing to weight gain and obesity.

Sensational claims about fasting “remain to be debunked”, Motara says. And while diet and stress may contribute to heart problems, “staying socially connected and being happy and content can also boost heart health”, he says.

That takes nothing away from the timeless words attributed to both Hippocrates and Mark Twain: “A little starvation can do more for the average sick man than can the best medicines and the best doctors.”

This article was originally published in Business Day. 

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