Intermitten fasting
Image Credit: Seyyed dela Llata / Gulf News


  • Some experts compare fasting to a “switch”, or “trigger", for several essential cellular functions. 
  • Intermittent fasting, or time-restricted fasting, done under doctor’s supervision not only helps you burn calories, and lose weight; it also enhances the mind — what neuroscientists call “cognition”.
  • Experts say it’s not for everyone.

Medical evidence is mounting. Time-restricted feeding is gaining more adherents who are openly prozelytising about it.

Famous people, including Nicole Kidman, Chris Hemsworth, Jennifer Aniston and Halle Berry, to entrepreneurs James Swanwick and Ingrid De La Mare-Kenny, comedians Joe Rogan and Mindy Kaling are all known to be practicing intermittent fasting (the 16/8 type).

The list is growing.

Studies published in high-impact scientific journals show short-term benefits of 16/8 method, 5/2 method, 72-hour (3-day) or even 5-day fast. There’s no data yet on the long-term benefits for humans.

Meanwhile, an in-depth review of the science of intermittent fasting recently published in the New England Journal of Medicine sheds some light. Researchers combed through dozens of animal and human studies to explain how simple fasting improves metabolism, lowers blood sugar levels, lessens inflammation (which improves a range of health issues from arthritic pain to asthma); and even helps clear out toxins and damaged cells, which lowers risk for cancer and enhances brain function.

Many studies on animals and humans show intermittent fasting leads to the following benefits, at least in the short-term:

  • Improves glucose tolerance.
  • Lowers blood sugar levels (through from improved glucose tolerance).
  • Lessens inflammation.
  • Expels body toxins.
  • Improves blood pleasure /resting heart rates.
  • Improves cognition.
  • Stimulates cell division without mutation or cancer cell formation.
Intermitten fasting
Image Credit: Seyyed dela Llata / Gulf News

What are the advantages of intermittent fasting?

Fasting helps burn the fat in the liver through a process called “glycogenolysis”, explains Dr Samir Rahmani, a UK-trained bariatric surgery specialist.

In medical science, fasting is considered a form of “detoxification”, which in turn stimulates cell division without mutation or cancer cell formation.

Another benefit: It is also known to stimulate bone marrow stem cell formation and helps lysosome to remove toxins from cells.

A short-term study published in the journal Cell Metabolism shows that early time-restricted feeding improves insulin sensitivity, blood pressure, and oxidative stress, even without weight loss in men with “pre-diabetes”.

Intermitten fasting
Image Credit: Seyyed dela Llata / Gulf News

What happens when you fast?

In a nutshell, fasting changes your “hormonal axis”, a Dubai-based expert said.

“Fasting, in general, improves your glucose tolerance,” said UK-trained surgeon Dr Samir Rahmani, head of bariatric and laparoscopic surgery at Novomed Centres Dubai.

“It is a major thing when we have glucose intolerance, when you have insulin resistance, pre-diabetes and all these sequelae [the consequence of a previous disease or injury]. And that’s why expulsion of toxins change your ‘hormonal axis’, mainly the gut hormones,” he added.

Why is fasting known as “anti-inflammatory”?

Dr Rahmani told Gulf News: “By fasting, you create an anti-inflammatory status. Our body is a balance of pro- and anti-inflammatory states. Any change in this equation will lead to more inflammation — or less inflammation.

“Fasting increases your defence mechanism to be in an anti-inflammatory state. Anything that creates pro-inflammation in your body — like a toxin, bug, bacteria, trauma or stress — this will be balanced by fasting, by improving your anti-inflammatory state.”

He added: “And that is what we achieve sometimes when we do this forcefully with surgery. When we do bypass, for example, and change the ‘plumbing’ of the gut. This is mainly to achieve a state of fasting.”

Dr Rahmani, a UK-trained surgeon, practises 72-hour (3-day) fasts. He has performed metabolic and bariatric surgery on more than 4,500 patients in his career.

How does fasting help expel body toxins?

Dr Rahmani said: “Fasting improves glucose tolerance, expels body toxins and burns the fat in the liver, in a process called glycogenolysis… splitting the fat stored in your liver, this is the first stage of fasting.”

“You actually kill any aged cells in your body by having no energy. The small, young cells will not wait for the fat to be burned in the liver; instead, they will gain energy from your arm, omentum or back. Unlike young cells, which can survive more while fasting, the aged cells will die straight away."

How do these aged cells die?

Obviously, aged cells have lots of toxins.

“Toxins are produced in any cell and in anybody. It’s a side product. Just like when we eat our body absorbs the nutrients and there will be byproducts, which we push it out [through excretion]. The same thing with cells.

“There is cellular metabolism, in which the cell would take its benefit from the energy (supplied) — such as ATP [adenosine triphosphate, a substance found in cells that provides energy for metabolic processes] — and then any byproduct will be toxins. With time, a cell will have lots of toxins. We need to expel it. But we can’t expel it under normal circumstances. That’s why fasting is important because aged and abnormal or bad cells will be very sensitive to a short term of fasting. They just die straight away. They lack the tolerance to resist any lack of energy.”

• It is the biochemical pathway in which glycogen (store of carbohydrates in the body) breaks down into glucose-1-phosphate and glucose.

• The reaction takes place in the hepatocytes (liver cells) and the myocytes (muscle cells).

• This process is under the regulation of two key enzymes: phosphorylase kinase and glycogen phosphorylase.

What happens when you continue fasting?

“If you continue fasting,” Dr Rahmani says, “it (glycogenolysis) will move on to the adipose tissues…the tissues that are in the rest of your body [basically, connective tissues consisting mainly of fat cells].”

Adipose tissue (AT) dysfunctionality is clearly associated with the onset of important pathologies, including obesity, Type 2 diabetes, dyslipidemia or non-alcoholic fatty liver.

Does fasting help reverse diabetes?

For Type 1, or insulin-dependent diabetes, fasting doesn’t help, Dr Rahmani said, adding that it will in cases of non-insulin-dependent diabetes (or Type 2). "This [the effectiveness] depends on the type or sub-type of Type 2 or non-insulin-dependent diabetes. Is it due to insulin resistance, high body weight, or your pancreas producing some antibodies?

"In general, if you have insulin resistance or high body mass index (BMI), you will benefit from intermittent fasting. The most important thing is to drop your sugar level, the HbA1C, which is a snapshot of your average blood sugar over the last 90 days.

Image Credit: Jay Hilotin

"If you drop it [the sugar level] to below 6 by IF [intermittent fasting], and reduce your weight, you will become healthy. Because a healthy person has an average HbA1c [sugar level] of less than 6. So you’ll actually be curing diabetes. This is for Type 2, or non-insulin dependent, diabetes."

415 m

Number of people with diabetes worldwide (Source: CDC)

What are the downsides of intermittent fasting?

It’s a trendy weight loss plan, seen as a workable antidote to Type 2 diabetes, and high cholesterol issues, among others — but experts say some people should avoid it.

When you aren't getting the amount of food your body is "used to” having, via intermittent fasting, it puts your body in a high-stress situation.

This causes more stress which can be taxing on your nervous system which can lead to fatigue, burnout, low energy, low body temperature, and a decrease in hormone function, experts warn.

While studies have shown that intermittent fasting can lead to short-term weight loss, the long-term effects of restricting calories in this way are still not fully understood, according to Dr Rahmani.

How does fasting reduce insulin resistance?

In general, studies show that fasting lowers the risk for Type 2 diabetes, a chronic disease affecting about 415 million people worldwide, according to the US Centers for Disease Control. If no intervention is done, that number could balloon to more than 500 million in 10 years.

Type 2 diabetes mellitus (DM) has two key features: high blood sugar levels and insulin resistance.

In general, anything that reduces insulin resistance should help lower blood sugar levels and protect against Type 2 DM. This is where intermittent can help greatly, demonstrating major benefits for insulin resistance, leading to reduction in blood sugar levels.

RECENT fasting studies:
• A 2020 randomised trial looked at people who followed the 16/8 method (fast for 16 hours a day and have an 8-hour window to eat a healthy diet).

• The people who fasted didn’t lose significantly more weight than the people who ate three meals a day. However, a subset of the participants in person tested by researchers showed the people who fasted lost a significant amount of lean mass. This included lean muscle.

• According to a 2014 review of the scientific literature, intermittent fasting can cause weight loss of 3–8% over 3–24 weeks.

• The study participants also lost 4–7% of their waist circumference over 6–24 weeks, an indication they lost visceral fat — the harmful fat in the abdominal cavity that causes disease.

• A 2011 review also showed that intermittent fasting caused less muscle loss than continuous calorie restriction.

In human studies on intermittent fasting, fasting blood sugar has been reduced by 3–6% over the course of 8–12 weeks in people with pre-diabetes. Fasting insulin has been reduced by 20–31%. One study in mice with diabetes also showed that intermittent fasting improved survival rates and protected against diabetic retinopathy — a complication that can lead to blindness. This shows intermittent fasting may be highly protective for people who are at risk of developing Type 2 diabetes.

Why should we fast intermittently?

"We do it for three main reasons," said Dr Rahmani. "(A) We need to lose excess weight. Anybody who can drop excess weight — 20kg or 50kg — the conservative or natural way, then that’s good. (B) When people need to maintain their weight. By doing that, there’s no need to intervene. (C) By doing A & B, by default, they will improve their health or cure their morbidities (like diabetes, blood pressure and cholesterol).

"If somebody weighs 100kg and he’s 160cm tall, it means he has 40kg of excess weight. If he can lose 30kg of that by fasting, dieting, and exercising, then there's no need for [surgical] intervention. They need to maintain it, too. So when a person is on a keto diet loses 10kg and regains 20kg on a 'rebound', it doesn’t work. I don’t believe in keto diet."

Does fasting improve your skin?

It does, eventually. But not during the fasting period.

The main idea is this: Fasting is “evolutionary”. It is embedded within our physiology. When we fast, it triggers several essential cellular functions. So “flipping the switch” from a fed to a fasting state does more than help us burn calories and lose weight.
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Dr Inaam Faiq, a general practitioner and aesthetic specialist at CosmeSurge Jumeirah and a member of the American Academy of Antiaging Medicine, said: “First of all, fasting is good for you spiritually. Nowadays, you hear a lot of celebrities doing intermittent fasting and declare that they feel healthier, more energised and are losing weight.”

WHAT IS circadian-rhythm diet?
The circadian rhythm diet, also known as the body clock diet, is a form of time-restricted eating plan where you eat in sync with this internal clock. "This means that you eat during the daylight hours, within a window of 12 hours or less and fast for the remaining 12 or more hours each day. Some only restrict their diet to 6 to 8 hours," Dr Faiq said.

She recommends that people “use an eating approach that works for them and is sustainable.”

A word of caution

Experts say that all things considered, intermittent fasting has the potential to be a powerful weight loss tool. As you eat fewer calories, it boosts metabolism slightly and is an effective tool against visceral fat.

Experts caution that people with advanced diabetes or who are on medications for diabetes, people with a history of eating disorders like anorexia and bulimia, and pregnant or breastfeeding women should not attempt intermittent fasting unless under the close supervision of a physician who can monitor them.

Before starting to fast intermittently, it is best to consult your physician and/or dietician to ensure you’re doing it right.