When people want to lose weight, the potential benefits of fasting can seem very appealing, because just having a certain window to eat means you potentially consume fewer calories.
But what is fasting? According to registered dietitian marcela fiuza (opens in a new tab)a spokesman for the British Dietetic Association (opens in a new tab), fasting means not consuming calories in a given period of time. It can be ‘intermittent’, which means you switch between eating and fasting, or ‘prolonged’, which usually means fasting from two days onwards.
“intermittent fastingin particular time-restricted eating such as 5:2 either 16:8It has become popular in recent years,” he adds. “It’s about eating within a restricted time frame each day, usually eight to 10 hours.”
Aside from weight loss, many people fast solely for the potential benefits, which include better gut and heart health, as well as lower blood pressure. But it is important to note that fasting does not guarantee these results and is not suitable for everyone, especially people with eating disorders, pregnant women, diabetics, the elderly and children.
In this article, we talk more with Fiuza about the potential benefits of fasting, and also take a look at some of the cons.
What does fasting do to the body?
Before discussing the potential benefits of fasting, it’s important to know what it actually does to the body.
Fiuza explains: “During fasting, the body goes through a series of metabolic adaptations to continue to function optimally in the absence of external fuel (food). In the first few hours of fasting, the body draws on its glycogen stores for energy. Once these are depleted, there is a metabolic switch, in which the body begins to break down fatty acids into ketones which are then used as a source of energy.
Marcela Fiuza is an award-winning registered dietitian based in London, UK. She has a decade of experience working in the NHS, private practice and the commercial sector. She has a Master of Nutrition and a Postgraduate Diploma in Dietetics from King’s College London. She is a member and media spokesperson for the British Dietetic Association.
“The timing of 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, you can go 12 to 26 hours without eating.”
Of course, not all benefits are guaranteed. “Many studies, mainly in animal models, suggest the benefits of fasting, and there is also growing evidence emerging from human trials,” says Fiuza.
“But more research is needed until we can fully understand the long-term impacts of fasting on human health.”
1. Autophagy
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 kind of quality control for your cells, autophagy allows the body to break down and reuse old cell parts so they can function more efficiently.
Put simply, it’s the body’s way of cleaning up and getting rid of mutated cells that could turn into cancer or neurological conditions like Alzheimer’s or Parkinson’s, according to a study in the EMBO Magazine (opens in a new tab).
The autophagy process begins after a period of fasting and could be an evolutionary throwback to our hunter-gatherer days, where people went longer without eating due to the laborious nature of finding food.
Researchers are studying the role of autophagy in preventing and fighting disease, says Fiuza. “Evidence from a study published in direct science (opens in a new tab) suggests that fasting may enhance autophagy.” Another study, published in Autophagy Diary (opens in a new tab)revealed that regular fasting could “reset” the body and help it function more efficiently by removing cellular waste.
2. Improved gut health
There are evidence (opens in a new tab) to suggest that a radical change in diet, such as fasting, could alter the microbial makeup of the gut and change what gut bacteria do.
Fiuza told WordsSideKick.com: “Some forms of fasting may be beneficial to the gut microbiome, which has been linked to a variety of health benefits of better metabolic health, reduced risk of cancer, heart disease and obesity.”
Other research found that alternate day fasting (24 hours of normal eating followed by 24 hours of fasting) promoted ‘bacterial clearance’ that could support gut microbiome health.
3. Healthy blood sugar levels and heart
Fasting can also improve the body’s response to the hormone insulin, which controls blood sugar levels. When blood sugar levels are regulated, the risk of weight gain and diabetes, which are two risk factors for cardiovascular disease and other heart-related health problems, is reduced.
Fiuza adds that intermittent fasting could also improve heart health by lowering low-density lipoprotein (LDL), or bad cholesterol, as well as “exerting positive effects on blood pressure regulation and reducing inflammation,” but more research is still needed in this area.
4. Weight loss
Fasting has gained popularity as many people see it as a way to lose weight. “It can potentially help some people lose weight in the short term,” admits Fiuza. “Although it does not appear to be superior to other types of calorie-restricted diets for this purpose.” And ultimately, to lose weight, you need to be on a calorie deficit.
A systematic review in a peer-reviewed journal canadian family doctor (opens in a new tab) found that in all 27 trials examined, intermittent fasting resulted in weight loss, ranging from 0.8% to 13.0% of baseline body weight.
But as with all extreme eating plans, there are some downsides to consider, says Fiuza.
“There are possible side effects of fasting, but most of the time they go away with time. The main ones are lethargy, irritability, and headaches, but there is also a risk of eating disorders for those with a predisposition to eating disorders.
“Extended fasting is much more intense than intermittent fasting and anyone considering doing it should talk to their healthcare professional beforehand. Intermittent fasting may also not be appropriate for everyone.
“People who are pregnant or have type 1 diabetes, have an eating disorder, or take medication with food, as well as children and older adults, should avoid fasting.”
If fasting doesn’t sound appealing, check out our guide to fasting. Mediterranean diet instead.
This article is for informational purposes only and is not intended to offer medical advice.
