Bollywood superstar Hrithik Roshan is said to swear by it. Hugh Jackman used it to help get lean while putting on muscle during his stint as X-Men’s Wolverine. Chris Hemsworth used it to slim down after ripping up for Thor. Benedict Cumberbatch used it to transform between the bulked-up superhero Dr Strange and the slim Sherlock Holmes.

All of these celebrities have turned to fitness’s latest darling – short-term fasting.

Fasting has been practised for thousands of years with many religions advising it as part of certain rituals. According to experts, the fact that we eat unhealthily and all day long are reasons we put on excess weight, feel tired easily and experience stress. Fasting, they say, could be a relatively easy way to lose weight, gain muscle, protect from diseases, increase mental focus and live healthy.

The practice involves skipping several meals, and could range anywhere from a 10-hour to a 24-hour or even a 72-hour fast, done on alternate days or just once a week. Types include a partial fast, where you eat a selection of solid food. Or a bone broth fast, where you consume bone broth and little solid food over two to three days.

In the simplest of terms, fasting is simply a continuation of what you do at night when you sleep, i.e. not eat. It’s a cheap, pretty straightforward approach. There’s no checklist to obsess over, because there’s no food to be had. Proponents say it also serves to teach you mind control, and to cope with the discomfort of hunger.

Victoria Tipper

So, will it kill us? Negative. Dubai-based nutrition and life coach and fitness trainer Victoria Tipper, says our bodies are genetically adapted to deal with fasting. ‘Consider our hunter gatherer ancestors,’ she says. ‘They would often go for long periods without food; we are programmed to be able to survive in such states.’

The rise of intermittent fasting

So, how do you prepare to fast? ‘Fasting really depends on the individual,’ says Victoria. ‘If you choose to try fasting, explore what works for your body and lifestyle and what works specific to your goals – for example a bone broth fast can be great for gut healing.’

But, she says, ‘something that I find more sustainable is intermittent fasting.’

This involves periods of eating and fasting – eating only during certain windows of time. Typical versions of this include eating eight hours and then fasting 16 hours. For example, eating between 8am to 4pm, instead of the usual 8am to 10pm. Some even choose to fast for 24 hours once or twice a week, eating normally the other days.

‘Many people are able to lose weight through intermittent fasting for many reasons. First, it is likely you consume fewer calories when you cut out entire meals. Fasting helps weight loss as it puts your body into a fat-burning state, breaking down the body’s fat stores to be used as fuel.

‘If done correctly, intermittent fasting can reduce oxidative stress and inflammation (key factors leading to chronic disease). This has been shown to help alleviate symptoms of those with asthma.’

It also helps boost immunity, says Victoria. It balances fat-regulating hormones such as adiponectin (fat burning) and leptin (that controls satiety). It improves blood pressure, blood sugar and cholesterol levels (improving triglycerides and LDL particle size, while increasing HDL cholesterol). Studies have also shown intermittent fasting helps the body deal with stress at a cellular level as the fasting itself causes a stress response to be activated in the same way a mild stressor would. Over time this consistent build up makes our cells more resilient to stress, reducing cellular ageing and disease development.

Beware the junk food

For fasting to work, you can’t be chomping on burgers and jalapeno cheese fries and washing it down with sodas when your window for eating opens. Fasting and then bingeing is counterproductive. Quality matters; you have to eat like a grown-up – cue the good foods and in moderation.

Victoria stresses the importance of making the calories you consume while on an intermittent fast count. ‘Go for a meal with adequate protein,’ she says.

‘It will probably be the main source of calories. This will help you to feel fuller for longer and prevent muscle breakdown.

Fill your plate with veggies; they are low in calories, says Victoria. They will help to fill you up as well as offer an array of important micronutrients. Add flavour with herbs and spices - again low in calories. ‘You can add spices like cinnamon, ginger and turmeric to help balance blood sugar levels to the low-carb meal as this will mean you are less likely to feel hungry so soon. It is OK to add a little fat as it will help you to feel fuller for longer but be sure not to go overboard.’

She lists various foods to avoid, including grains and starchy carbohydrates such as potatoes, rice, pasta or too much fruit and anything with sugar. Being high in calories, these will only cause you to feel hungry again soon after, due to their effect on blood sugar levels.

Eat healthy and stay hydrated

Dr Ayla Coussa

Dr Ayla Coussa, Clinical Dietician at Bareen International Hospital – Mohammad Bin Zayed City, Abu Dhabi, echoes this mindful approach when on an intermittent fast. ‘Given that the eating period is limited, it is important for dieters to focus on nutritious foods to fuel their body with the required nutrients. High-fibre foods induce a longer sensation of satiety and energy-level: whole grains, oats, legumes, etc. Protein-rich and healthy fats (such as avocado) also promote fullness. Simple sugars should be avoided as they induce a sharp increase followed by a drop in sugar levels which can lead to fatigue and reduced energy levels.’

And beware of your cappuccino intake; opt for water instead. Caffeine will cause an increase in the stress hormone cortisol, which signals the body to store fat. ‘This increase in cortisol can also exacerbate stress levels. A better idea is to have green tea (which has a little caffeine and L-theanine, a calming amino acid) and of course lots of water.’

A little awareness can go a long way

Like most things, there are caveats when it comes to fasting. Some nutritionists believe that if you are not careful, fasting can be a slippery slope to eating disorders and unhealthy food habits. Prior to fasting, it’s important to know how your body reacts to stress.

Victoria says it is important to realise that fasting is not a type of diet, but merely a schedule for eating. It is important to make sure intermittent fasting is done correctly, focusing on eating a diet full of whole foods and avoiding processed foods.

For those who have food sensitivities and intolerances to foods such as dairy, soy, gluten and artificial sweeteners, continuing to avoid these foods in the eating hours will enable them to see the best results. ‘Also, often in intermittent fasting, people consume larger meals in a smaller eating window that could put extra pressure on the digestive system,’ she says. ‘This is especially apparent for those with existing digestive symptoms such as IBS or issues with bloating or acid reflux. It is also wise to avoid intermittent fasting if you have a history of eating disorders as it might trigger unhealthy eating patterns.’

Those who suffer from low blood sugar have to be careful, as fasting can cause blood sugar levels to drop too low, resulting in symptoms like fatigue, palpitations and shakiness, she says. While intermittent fasting has been shown to help conditions like diabetes, it is extremely important that the individual consults a medical professional before fasting.

Victoria also raises a less-thought-of aspect. ‘Fasting might also bring with it some awkwardness in social situations, where others are meeting and dining outside of your eating window. This can leave a person feeling left out, so it is good to have a response ready and prepared for such times. Not eating can also bring with it some uncomfortable physical symptoms for some, for example some may experience constipation, fatigue, lack of concentration and focus, headaches, bad temper (or what’s commonly known as hangry, that’s anger due to hunger).’

Importantly, it is not appropriate for everyone. ‘People who are underweight (with a BMI lower than 18), with a history of eating disorders, diabetes or other medical conditions, pregnant or breastfeeding women, as well as children, teenagers, and athletes are strongly recommended to consult their doctor before going on such diet plans,’ says Dr Coussa.

If you are still tempted to go on a fasting diet, Dr Coussa says healthy eating habits and nutritious foods on non-fasting days can help. ‘Remember, there is no one-size-fits-all diet or a magical solution. The best diet remains the one that is customised to your body and lifestyle and will help you achieve and maintain a healthy weight, physical and mental well-being.”