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Considering fasting? Read this first

If you’re thinking of trying a fast, Ramadan is a very good time to do it. But what are the rules? How many hours should you be abstaining from food? Are you still allowed tea and coffee? Should you try intermittent fasting or a fasting mimicking diet or something like the 5:2? Or should you dive straight in with a prolonged fast?

Which one best suits your goals? Are you looking for weight loss, better skin, improved sleep? And are you aware of the negative side effects that can affect certain groups? 

It’s complicated.

Research on the subject of fasting is still not very advanced and much of what there is has been carried out on small sample groups or on animals, so there isn’t much to support, or negate, the claims made by some of these diets. So before you do anything else, seek independent advice from your doctor or a nutrition professional.

We asked three experts – two of whom fast regularly for the benefits – what you need to know. 

Is fasting actually good for you?

Nasr Al Jafari functional medicine

Dr Nasr Al Jafari functional medicine practitioner and family medicine consultant at DNA Health Center in Dubai

Dr Nasr Al Jafari is a functional medicine practitioner and family medicine consultant at DNA Health Centerin Dubai, as well as a member of the Livehealthy expert panel. He has incorporated regular fasting into his diet.

“Fasting should be a non-negotiable for near enough everyone,” he says. “It’s a practice which has been implemented across the centuries by pretty much every culture. Top health issues, such as cardiovascular disease, diabetes, obesity and dementia are linked in some way to our eating habits, one of which is eating food over an unnaturally protracted period of time and being in a ‘fed-state’ rather than a more natural ‘fasted-state’ for longer periods of time.”

Jenna Hope, a nutritionist and influencer from Jenna Hope Nutrition, advises clients on the pros and cons of fasting.  She agrees there are positive impacts of fasting, but is also more cynical about some of the drawbacks.

“I think one of the main benefits is to encourage people to stop grazing in the evening after dinner when they’re not hungry. It’s important to be aware that it can be detrimental to those with a poor relationship with food and it can be counter-productive in understanding your appetite signals. I don’t support the long periods of 24 hours-plus, as I think that can pose a risk of a poor relationship with foods and deficiency in micronutrients.”

Fasting for weight loss?

Mays Al-Ali is nutritionist, yoga teacher and blogger at (File Photo) via:

Mays Al-Ali is nutritionist, yoga teacher and blogger at, who supports routine fasting as part of a healthy diet.

“Obviously when you are fasting, you are reducing your overall calorie intake, which leads to increased weight loss over time,” says Mays Al-Ali. “Short-term fasting is also known to boost your metabolism by increasing levels of a neurotransmitter called noradrenalin, which aids weight loss. Also fasting has been shown to be more effective than calorie restriction at increasing fat loss while at the same time preserving muscle tissue. Ketosis is another process that occurs later into the fast cycle and happens when the body burns stored fat as its primary power source.”

But Jenna Hope adds a word of caution. “For individuals who are not eating enough calories there can be negative effects like undesirable weight loss, increased nutrient deficiency risks and fatigue. While there is not enough evidence to conclusively suggest that fasting may contribute to eating disorder risk, it’s definitely not recommended for anyone with a poor relationship with food. Some evidence suggests long periods of fasting [24 hours] may increase overeating outside of the fasting window.”

What happens during a fast?

“When we fast, the body does not have its usual non-exhaustive access to glucose, either from diet or from glycogen stored in the liver,” explains Dr Al Jafari. “This forces the cells to resort to other means and materials to produce energy. As a result, the body begins a process called gluconeogenesis. This is when the liver helps by converting non-carbohydrate materials like fats and amino acids into glucose. Far from being abnormal, this is a fundamentally natural process which we are adapted to go through on a regular basis.”  

Fasting for cell rejuvenation?

“Essentially, fasting cleanses our body of toxins and forces cells into processes that are not usually stimulated when a steady stream of fuel from food is always present,” explains Mays Al-Ali. “Our body uses 80 percent of its energy to digest food, so when we aren’t digesting food during fasting, we can use that energy to get rid of old cells and create new cells and make the body healthier. It’s a process known as autophagy. Fasting puts the body under mild stress, which makes our cells adapt by enhancing their ability to cope. In other words, they become stronger. This process is similar to what happens when we stress our muscles and cardiovascular system during exercise.”

“The results of this are far reaching,” adds Dr Al Jafari, “with both mental and physical benefits including reduced inflammation, prevention and reversal of metabolic diseases, improved focus and cognition. Studies have also demonstrated a reduced risk of cancers and a protective role in developing dementia.”

Who should not fast?

Jenna Hope

Jenna Hope, a nutritionist and influencer from Jenna Hope Nutrition (File Photo) via:

“Those with diabetes or medical conditions, and those with a history of a poor relationship with food should avoid fasting,” says Hope. “Those with medical conditions may be able to fast if they have permission and specific personalised advice from their GP. Pregnant women should avoid fasting due to the increased demands on their bodies for nutrients and energy.”

What about intermittent fasting?

“This is the process of limiting calorie intake to a specific time frame within a single day, that aligns with our ‘body clock’ – the natural cycle that tells our bodies when to sleep, rise, eat and more,” says Dr Al Jafari. “This can mean having your meals in an ‘eating-window’ of less than 12 hours, while spending the rest of the day fasting from food and calorific drinks.” 

Many people choosing this fast opt for the 16:8 diet, which limits eating to an eight-hour period every day, followed by 16-hours of abstaining. 

“Fasting within a time period can be a way to manage calorie intake due to the reduction in snacking and grazing outside of these hours,” explains Hope.  “However, some individuals have reported that fasting  meant they simply ate all their usual calories within a shorter time frame rather than reducing the total umber of calories they consumed, so fasting does not necessarily reduce calorie intake automatically.”

What about prolonged fasting?

“This is the practice of fasting for longer than a 24-hour period, and sometimes even longer,” says Dr Al Jafari.  

His fasting practice involves a combination of six days a week of 16:8, one day a week of 24-36 hour fast, and seasonally undertaking a 72-hour fast in an effort to alter how the environment influences the expression of his DNA, also known as epigenetics. 

“The evidence seems to suggest that fasting for three to five-day periods are extremely effective at modifying the epigenetic marks associated with ageing.” 

During his fasting period, Dr Al Jafari consumes only water, herbal teas and black coffee. 

Can you explain periodic fasting?

The most famous of these is the 5:2 diet. 

“This involves eating for five days and limiting calories to just 500 for the other two days,” explains Al-Ali. “The suggestion is to enjoy three smaller meals or two slightly bigger meals during the calorie restricted days. And spacing the fasting days between eating days will help curb hunger too. There is positive research on the 5:2 diet leading to weight loss and improved insulin balance compared to calorie restriction alone.”

What are fasting mimicking diets?

“This means limiting calorie intake for three to five days, prompting the cells to deplete glycogen stores and begin ketosis,” says Dr Al Jafari. “A specific five-day calorie-limited diet (around 900-to 1,000 calories per day) is sufficient to mimic fasting without depleting nutrients. It is speculated that this method is as effective as prolonged ‘water-only’ fasting.”

What negatives come with fasting?

“Some people can get short-term transitional symptoms when they initially start, such as dizziness, hunger, lethargy, headaches and so on,” says Dr Al Jafari. “Some people can get disturbed sleep when entering ketosis during longer fasting.”

Al-Ami recalls one of her first fasts: “I did a seven-day fast without doing prior research, and before training as a nutritionist. I felt fatigue, I had a rash come up, I felt quite unwell,” she remembers. “This was a sign that my body was detoxifying: when we fast we release toxins from the blood into the body and they need to be excreted using things like chelating agents – for example, chlorella, activated charcoal, coffee enemas or colonics. If we don’t do this then we may feel these symptoms.”

What about hunger?

“I don’t usually get hungry during intermittent fasting and during longer fasts the body gets used to it and the hunger reduces,” explains Al-Ali, who practices a 16-hour fast most days, regularly extending that to 18 or 20 hours. 

“But if you do feel hungry, drinking water is a great idea or herbal teas. If during an extended fast you don’t drink enough water and then eat a large amount, it could cause mild constipation, so keeping hydrated during a fast is important.”

What benefits should you feel?

“Most people who have completed longer fasts rave about the improvements in focus, clarity of thought, increase in energy and loss of hunger cravings,” says Dr Al Jafari. “Beyond this, we have applied long water-only fasting to treat gut issues, inflammatory conditions and to improve body composition.”

Al-Al draws from personal experience: “I always feel amazing after a fast: more energy, clearer skin, brighter eyes.”

Should you still exercise?

“Generally speaking, training during fasting is encouraged,” says Dr Al Jafari. “But I would not normally recommend doing an intensive session during long fasts, unless one is intending to break  a fast soon after. I tend to favour resistance training, as it has muscle promoting benefits even during short-term nutrient deprivation.”

How can fasting affect women’s hormones?

“On the positive side, fasting can help balance blood sugars, aid weight loss and improve digestion, which will all in turn help to balance female hormones and menstruation,” explains Al-Ali. “On the other side, if a woman loses a dramatic amount of weight or is consistently not getting enough calories, it could slow down or stop the menstrual cycle.”

Hope agrees: “The female cycle drives appetite at different times of the month; overriding this can make women irritable and lethargic.” 

What other negative effects can fasting have?

“Intermittent fasting overrides internal physiological hunger cues, meaning that it can impair the ability to eat mindfully and intuitively,” explains Hope. “Additionally, it may increase overeating during the non-fasting period and therefore is not always conducive to eating mindfully.”

Article contribution by Dr Nasr Al Jafari for

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