Experts reveal alarming impact of fasting on the body – as gut-wrenching simulation video leaves social media astonished

It’s a diet trend endorsed by everyone from Hollywood A-listers to Rishi Sunak.  

But, to the dread of dietitians across the planet, there’s an even more extreme version of ‘intermittent fasting’ being taken up by those wanting to lose weight—the OMAD diet.

An abbreviation for ‘one meal a day’, the trend does exactly what it says on the tin. 

Coldplay frontman Chris Martin reportedly swears by it after learning of the diet from legendary rocker Bruce Springsteen, whose wife is a proponent.

Yet experts have urged caution over its ‘short-lived’ effectiveness, warning it could trigger chronic health issues like digestive conditions and even life-threatening heart disease.

It comes as an illuminating video posted online this week garnered thousands of views for its alarming display of exactly what happens to the body —hour by hour— when fasting. 

The four-minute gut-wrenching simulation claimed the body stops digesting food after just four hours, entering what is known as the catabolic phase—when muscle and fat is used for energy.

By 12 hours, it has hit a ‘fasted state’ depleted of blood sugar. Here, the liver begins to break down stored fat into fatty acids called ketones to use as fuel. 

The simulation posted online used disturbingly detailed images to show exactly what happens as the body enters a fasted state

An abbreviation for ‘one meal a day’, the trend does exactly what it says on the tin. Coldplay frontman Chris Martin reportedly swears by it

Jennifer Aniston , Chris Pratt and Kourtney Kardashian are among the Hollywood A-listers to have jumped on the trend since it shot to prominence in the early 2010s. But, despite swathes of studies suggesting it works, experts have remained divided over its effectiveness and the potential long term health impacts 

But ketones can be dangerous—high levels of them in the blood can lead to a condition called ketoacidosis, when blood becomes too acidic. If not treated promptly it can be life-threatening.

Studies have also found that prolonged exposure to ketones can be detrimental to the heart, increasing the risk of heart attacks and strokes.

Fasting up to 16 hours can then stimulate autophagy— where cells break down and remove damaged or unnecessary components like old proteins—it is claimed. 

Research has long warned, however, that excessive or prolonged autophagy can lead to cell death, potentially harming organs.

Supporters of OMAD say it can boost productivity, improve memory and cognition, helps them manage their weight easier and keep fit.

OMAD was made famous by model-turned-actress Liz Hurley in the early 2000s, who was admired for her age-defying figure which inspired envy in women in their 20s.

The now 57-year-old admitted to limiting herself to just one meal per day after giving birth to her son Damian in 2002, confessing that she was ‘going to bed hungry’.

Other intermittent diets, such as the 16:8 eating plan, are based on entirely the same principal. But followers instead fast for 16 hours a day, and eat whatever they want in the remaining eight hours — typically between 10am and 6pm.

This can be more tolerable than the infamous 5:2 diet, where calories are restricted to just 500 a day twice a week.

In 2023, Coldplay’s Chris Martin revealed: ‘I stop eating at 4[pm] and I learned that from having lunch with Bruce Spingsteen’. Pictured above, svelte Springsteen performing in 2014 at the New Orleans Jazz & Heritage Festival

OMAD was made famous by model-turned-actress Liz Hurley. The now 59-year-old admitted to limiting herself to just one meal per day after giving birth to her son Damian in 2002, confessing that she was ‘going to bed hungry’. Pictured in London in January 2023 

By creating a calorific deficit during fast days, the body instead relies on breaking down stored body fats to to create energy, aiding quicker weight loss.

But sports nutritionist Abigail Roberts told MailOnline: ‘Unless the meal contains all the necessary nutrients and calories required by the body, it’s unlikely to be a healthy approach to eating, especially if done over a long period.

‘Research has shown that consuming only one meal a day can lead to inadequate nutrient intake, causing deficiencies that may lead to various health problems such as fatigue, weakened immunity, and impaired cognitive function.

‘Additionally, eating one meal per day may increase the risk of binge eating during that meal, causing digestive discomfort such as bloating and constipation.’

Intermittent fasting does have benefits ‘for some people’, Miss Roberts accepted. 

But she urged anyone looking to drastically cut weight — a theme at this time of the year when many are trying to get in shape for summer — to inform their doctor.

Dietician and spokesman for the British Dietetic Association, Dr Linia Patel, also told MailOnline: ‘Whatever weight loss or health benefits you see on the OMAD diet will likely be short-lived.

‘Not eating for 23 hours will likely lead to a lack of energy, fatigue, uncontrollable cravings, and disruptions to your bowel habits.’ 

She added: ‘This diet is not one I would recommend as it is too restrictive, can lead to fad dieting and disordered eating.

‘There is some positive research surrounding fasting in general, showing that fasting when done in the right context could aid in weight loss and assist in preventing chronic disease, 

‘If you do want to try intermittent fasting, at least go with the 16:8 method, which has you fasting for 16 hours and eating for eight. It’s not for everyone, but it’s a much more balanced approach. Speak to a dietitian for more tailored support.’

Professor Naveed Sattar, a professor of metabolic medicine at the University of Glasgow, said: ‘Any mechanism that helps people control their calorie intake will help them lose weight — the key issue is whether one meal per day is sustainable in long term.’ 

He told MailOnline: ‘It may not be for the vast majority of people. Rather small sustained changes in usual caloric intake with three meals per day maybe a better achievable goal for many.’

Research into OMAD specifically is still emerging. 

One 2022 study, however, found participants who only ate one meal per day saw a greater reduction in their body weight and fat mass. 

There was no difference in lean mass or bone density by the end of the 11-day trial, however, according to results of the 11-person project in the journal Frontiers in Physiology. 

A second study a year earlier in the Journal of Animal Science and Biotechnology compared the effects of eating one large meal a day against two or six in mice. 

Rodents on just one meal gained more weight than those who consumed multiple meals. 

Writing for The Conversation, Dr Amanda Avery, an associate professor in nutrition and dietetics, at the University of Nottingham also said: ‘There’s still a lot we don’t know about it.’

She added: ‘It’s also important to note that while this diet might work for celebrities, they also have access to nutritionists, high-quality diets and supplements where needed. 

‘For most of us, this kind of diet could be unsustainable – and potentially harmful in the long run.’