Does the 'one meal a day' diet work? Experts outline the pros and cons

Last month, British actress and former Bond girl Jane Seymour, 69, declared that one of the reasons she was confident she could play the role of a woman in her 20s was due to her “rigid self-discipline” in eating just a single meal a day, a dietary routine she has followed since she was 17.

While that might sound bizarre, a cursory glance at the almost-septuagenarian appears to back up her claim, as she certainly looks decades younger than her age.

The “one meal a day” (Omad) approach to dieting and calorie-intake has an army of ardent admirers, including Twitter chief executive Jack Dorsey, Kate Middleton’s socialite sister Pippa, and Hollywood stars Liz Hurley, Jennifer Aniston, Brooke Shields, Channing Tatum and Chris Pratt, among others.

Along with the Omad approach, old-fashioned calorie reduction neatly packed under new names and in new guises has become a favourite approach for those hoping to shed weight fast. Intermittent fasting; 5:2 (capping food intake to under 500 calories twice a week); alternate-day fasting (capping intake to 500 calories on alternate days); time-restricted windows of eating, such as 16/8 (fasting for 16 hours a day and eating within an 8-hour window), along with 24-hour fasts once or twice a week have become the latest fads to strike a chord with those looking for the next quick fix when it comes to diet and weight loss.

What is the one meal a day approach?

Omad works on the calorie-deficit principle. Most people with no major underlying health issues will lose weight if their bodies are forced into an eating regimen that significantly restricts the inflow of calories – if you are going to eat one meal a day, it is likely, in theory, that you will eat far fewer calories than if you were to eat three big meals, four medium meals or six small meals.

Dr Nicole Sirotin, chair of preventive medicine at Cleveland Clinic Abu Dhabi, explains how fasting essentially works. “Normally, glucose and fatty acids are the means of energy for cells. The body uses the glucose from our food for immediate energy, while the fatty acids are stored in our fat cells – the adipose tissues –as triglycerides. But when you’re fasting, those triglycerides get broken down and are used by your body for energy. The liver converts the fatty acids into ketone bodies, which the body then uses for energy.”

Since Omad is simply a more extreme form of fasting, if you don’t mind the continuous self-restraint and are in reasonably good health, it’s likely you will end up losing weight while on it. For those who find the mental gymnastics of continuously counting calories to be the most difficult part of committing to an eating plan, Omad does, to some degree, simplify things.

‘It is not sustainable’

Clinical dietician and founder of Simply Health Mitun De Sarkar, however, is not a big fan of the Omad approach. “My take on any extreme eating pattern has always been the same: it works for a short-term, but for most it is not sustainable in the long run.

“Having one meal a day is popular with some intermittent fasters as it gives them a longer window of fasting, but it’s important to ensure that even in that one meal, the dieter is eating healthy and making absolutely sure that they are getting all the important nutrients in the requisite amounts, and that they are not bingeing on high-calorie, high-sugar processed foods that will cause more harm to the digestive systems and cause other long-term issues. Having one meal a day is not a licence to eat junk once a day and then over-compensate for the rest of the time.”

Held hostage by the hunger hormone

Both Sirotin and De Sarkar offer some words of warning for those who might be contemplating following the one meal a day approach.

“The risk of increasing your levels of ghrelin – the hunger hormone – is very real,” cautions Sirotin. “And some might end up feeling more hungry and eating more calories than they would have if they were to spread their food intake through the day.”

De Sarkar adds: “The negatives far outweigh the positives. They include, but are not limited to, acid reflux due to long periods of not eating, low energy levels due to glycogen depletion, lack of focus as the brain thrives on glucose from natural foods.

“Diabetics may experience insulin-related problems if they practise it without proper monitoring and regulation, the blood pressure may drop and result in bouts of dizziness or even fainting. Not to mention that you will be constantly preoccupied with thoughts of food.”

The pros and cons of intermittent fasting

While the benefits and risks of intermittent fasting have been well-researched, multiple studies have concluded that when done right and with food from largely plant-based sources, the approach can lead to positive health outcomes. These include regulation of glucose, improved metabolism, reduction of insulin production, lower inflammation, and lowering the risk of cardiovascular diseases, as well as weight loss.

However, several studies have shown that in the absence of major caloric reduction, a dieter is likely to lose the same amount of weight with a controlled calorie diet as with fasting. What this means is that the weight loss impact for your body is going to be more or less the same if you eat 1,500 calories spread over three meals of 500 calories each, or one meal of 1,500 calories.

And because the Omad approach is still relatively new, there is a lack of research on its effects over a prolonged period, with no material long-term study to ascertain the impact of this style of eating on the body over months and years.

“My advice to anyone planning such an extreme form of dieting is to not use celebrities and other well-resourced individuals such as Jack Dorsey as benchmarks for comparisons,” says De Sarkar. “Get your tests done and seek guidance, but remember while it may work in the short term, health in general needs to be treated as a marathon – with very few sprints interspersed in between.”

OMAD checklist

· Get your blood-work and other essential tests done, as recommended by a qualified professional, to ensure there are no deficiencies or other issues that may cause medical problems arising from prolonged periods of no food.

· Don’t do it, especially unsupervised, if you have underlying conditions such as diabetes, blood pressure or heart-related issues or even vitamin and mineral deficiencies. If you are immunocompromised, the approach may lower your body’s immune response to pathogens.

· Women need to take particular care to ensure there are no hormonal disruptions.

· Pick your meal time carefully. Don’t eat too early in the day as it might make you lethargic and cause hunger pangs by the time you sleep. Don’t eat too late as it might cause fatigue and tiredness through the day.

· Watch out for red flags such as dizziness and sleep apnea. Keep a journal of energy levels and general mood through the day. If you start to feel lethargic or lose hair, you should rethink the diet and seek professional guidance.