Several health benefits of fasting, according to science

When people want to lose weight, the potential benefits of fasting can seem very appealing, because only having a certain window to eat means you potentially consume fewer calories.

But what is fasting? According to registered dietitian Marcela Fiuza, a spokesperson for the British Dietetic Association, fasting means consuming no calories in a certain time frame.

It can be ‘intermittent’, meaning you switch between eating and fasting, or ‘prolonged’, which generally means fasting from two days onwards.

“Intermittent fasting, in particular time-restricted eating like the 5:2 or 16:8, has become popular in recent years,” she adds. “It involves eating within a time-restricted window each day, usually eight to ten hours.”

As well as weight loss, lots of people do fasting purely for the potential benefits, including better gut and heart health as well as lower blood pressure. But it’s important to note that fasting is not suitable for everyone — particularly anyone with certain illnesses, pregnant women, frail seniors and children.

Before we look at the potential benefits of fasting, it’s important to know what it actually does to the body.

Fiuza explains: “During fasting the body makes a number of metabolic adaptations to keep functioning optimally in the absence of external fuel (food). In the first few hours of fasting, the body resorts to its glycogen stores for energy. Once these are depleted, there is a metabolic switch, in which the body starts breaking down fatty acids into ketones that are then used as a source of energy.

“The timing for this metabolic switch depends on what your last meal was, how much energy you use and the amount of glycogen stored in your liver. On average it can take 12-26 hours without food.”

One of the possible benefits of fasting is that it can trigger a process called autophagy — your body’s cellular recycling system. Acting as a sort of quality control for your cells, autophagy allows the body to break down and reuse old cell parts so they can work more efficiently.

Put simply, it’s the body’s way of housekeeping and getting rid of mutated cells that could develop into cancer or neurological conditions like Alzheimer’s or Parkinson’s, according to a study in the EMBO journal (opens in new tab).

The process of autophagy begins after a period of fasting and could be an evolutionary throwback to our hunter-gatherer days, where people would go longer without eating due to the labor-intensive nature of finding food.

Researchers are studying autophagy’s role in potentially preventing and fighting disease, says Fiuza. “Evidence from a study published in Science Direct (opens in new tab) suggests that fasting may be able to enhance autophagy.” Another study, published in Autophagy Journal (opens in new tab), revealed that regular fasting could ‘reset’ the body and help it run more efficiently by clearing out cellular debris.

There is evidence to suggest that a radical change in diet, such as fasting, could alter the gut’s microbial make-up and change what gut bacteria is doing.

Fiuza told Live Science: ”Some forms of fasting may be beneficial to the gut microbiome, which has been linked to a range of health benefits from improved metabolic health, reduced risk of cancer, heart disease and obesity.”

Other research found that alternate-day fasting (24 hours of eating normally followed by 24 hours of fasting) promoted ‘bacterial clearance’ that could support the health of the gut microbiome.

Fasting may also improve the body’s response to the hormone insulin, which controls blood sugar levels. When your blood sugars are regulated it reduces the risk of weight gain and diabetes, which are two risk factors for cardiovascular disease and other heart-related health problems.

Fiuza adds that intermittent fasting could also improve heart health by reducing low-density lipoprotein (LDL), or bad, cholesterol as well as “exerting positive effects on blood pressure regulation and by reducing inflammation”, but more research is still needed in this area.

Source: Live Science

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