A glass of water with lemon
Doctors have warned against "water fasting" Unsplash/JezTimmins

After weeks of Christmas indulgence, toning up and taking better care of our bodies will be a priority for many of us as we head into the new year.

"Water fasting" has emerged as a trend online as an apparent quick fix, but experts have warned that the regime is dangerous.

While the idea of not eating to lose weight is hardly ground-breaking, #waterfast has been appearing on social media as document their apparent commitment to the "diet", and draws up 17,000 results on Instagram alone.

What is water fasting?

As the name suggests, water fasting is a method of weight loss which involves cutting out all food. Instead, followers restrict themselves to three drinks in a day for an indefinite period of time. Only water, black tea or coffee can be consumed.

New York-based real estate broke Elan Kels claims he followed the water fast for 28 days before giving up.

WATER FASTING . So if you may or may not know, I've been water fasting for the past couple of days. Today marks day 9 of my fast. . I came across this topic a few weeks ago and I was pretty impressed about all the health benefits of water fasting and a little fascinated by its curing and healing purposes . So if you're not familiar with it, water fasting simply means: ONLY consuming water for a specific period of time. . Here are some of the reasons I decided to give it a try: - to give my digestive system a break - To get rid of possible parasites within my body, since they cannot survive for a long period of time without being fed (having parasites is far more common, than you think, google it!) - to heal my skin (I still struggle with hormonal acne, after dropping the pill over a year ago). Hormonal acne is, when you get pimples at your cheekbones, and jawline area. Hormonal balance within your body is SO important! I'm still on my journey towards it, but it takes longer when you do it all naturally. - To get rid of the unnecessary fat on my body, without losing all of my muscles and without having loose skin - Basically to reset my entire body and start fresh . So when you're fasting you will get in the state of ketosis. It means, that your body doesn't feed off of the food you're consuming, but off of your body's fat storage. This is the easiest way for your body to get its fuel from. When there is no more fat left on your body, it will target your muscles as it's fuel source. Studies have shown, that being in a caloric deficit actually leads to more muscle loss over time, than eating nothing! (This sounded very appealing to me 😃) After fasting you won't be left with loose skin, even if it's such a radical form of fat loss, because your body will also feed from your scar tissue. Basically your body will take anything possible as a form of fuel, to survive. When you are in ketosis your feeling of hunger (or appetite) will go away. It's actually not as hard as you think it is! BUT it takes strong willpower. It is only hard for me, when I smell food. . When NOT to fast: (READ IN THE COMMENTS)

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What do the experts say?

The consensus is that such fasts are dangerous if not completed to treat specific conditions with the supervision of a medical doctor. For the rest of us, it is little else than a grueling challenge that disturbs our metabolisms and leads to long-term weight gain and ill-health.

Clinical social worker Joanne Labiner told the New York Post that such a diet is a form of disordered eating.

Jo Travers, the author of The Low-Fad Diet, meanwhile warned in an interview with The Independent water fasting cuts out vitamins, minerals or protein "which means the body has to break down muscle in order to recycle the amino acids into hormones and enzymes to stay alive."

"You are basically starving yourself and that comes with huge health risks," she added.

She also highlighted the dangers of such a regime being labelled as a "cleanse" or "detox", calling these "meaningless terms" and slamming is as neither healthy nor balanced.

Dr Jason Fung, kidney specialist and author of The Complete Guide to Fasting, told Mail Online that a short term water fast could be beneficial for those who are obese or have Type 2 diabetes - but only when prescribed by a doctor.

"If you're relatively slender, it's more dangerous [than if you are obese]," he said. "The longer you [fast] the more risks you take," he added.

Starvation diets are particularly dangerous for those with blood glucose regulation issues such as Type 2 diabetes, insulin resistance, hypogylcaemia and impaired glucose tolerance, warned nutritionist Susie Burrell in an article for news.com.au.

As the body's source of fuel is cut, the metabolic rate slows and stress is placed on the body's cells and organs as they struggle to function without fuel. More generally, long-term slowing of the body's metabolic rate will cause a person's weight loss to plateau. And any body mass lost will be quickly regained when the person starts to eat normally again.

What is the best way to lose weight?

"Instead of setting yourself restrictive goals like 'cut out' chocolate or 'avoid carbohydrates' or 'limit portion sizes', try and phrase it to yourself in positive light 'enjoy chocolate in sensible amounts' or 'choose portions that match my needs' - as soon as you change your language, you are feeling less restricted and more in control," dietician Aisling-Pigott recently told IBTimes UK.

She added: "Set yourself small, realistic goals of one to two pounds a week. We are often so keen for that magic, quick solution, we forget that maintainable weight loss doesn't happen overnight."