Fasting has been one of the biggest diet trends to hit the headlines in recent years, and its latest iteration is the OMAD diet. The OMAD – which stands for One Meal A Day – follows one very simple rule: eat only one meal a day, which in turn, requires significant stints of fasting, not to mention, self disclipline.

OMAD is growing in popularity, with high-profile men in particular (Coldplay’s Chris Martin, Bruce Springsteen and UK PM Rishi Sunak all rumoured to be fans) adding to the hype. But what’s the science, and why is it that men in particular seem to rate the OMAD diet?

“OMAD is a form of intermittent fasting and although the research in this area is still growing, some rodent studies suggest intermittent fasting may affect oestrogen levels and have a negative flow-on impact on menstrual regularity, fertility, pregnancy, and lactation,” explains The Lifestyle Dietitian’s Erika Hung. “Hormone levels of male rodents are also affected, but this doesn’t seem to change their reproductive functions as much as they do for female rodents.  Perhaps this is why men seem more drawn to OMAD as less negative side effects are experienced. But the jury is still out!”

What Is the OMAD Diet?

The OMAD diet is an intermittent fasting approach that centres around the consumption of just one meal per day, with an extended fasting period in between. Typically, OMAD devotees eat their meal within the same 1-2 hour window, fasting for the remaining 22-23 hours of the day. OMAD is super restrictive, which, experts say, is the reason why you might see results…at least in the beginning. “Eating one meal a day significantly reduces how many calories you eat – that’s two whole meals and at few snacks completely cut out! This would cause weight loss initially,” explains Erika, who is also an accredited practising dietitian.

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Principles of the OMAD Diet

  1. Eat once a day: As the name suggests, you’ll consume all your daily calories and nutrients within a single meal.
  2. Fast for extended period: The rest of the day is dedicated to fasting. During this time, you can consume water, herbal tea, and black coffee to stay hydrated and curb hunger.
  3. Caloric intake: While OMAD allows for flexibility in food choices, it’s important to ensure that you meet your daily caloric and nutritional needs within your one meal. It’s not an excuse to overindulge or skip essential nutrients.

Purported benefits of the OMAD Diet

  1. Weight management: By design, OMAD naturally limits caloric intake and creates a calorie deficit which can lead to weight loss.
  2. Simplified eating: OMAD simplifies meal planning, making it easier to maintain a healthy diet and control portion sizes because you’re only worried about planning one meal.
  3. Time and money savings: With only one meal to prepare and eat, you can save time on food prep and cash on your food bill.

Health risks of the OMAD Diet

Like most fad diets, OMAD comes with a long list of health risks, that spans the physical, emotional and mental. Ultimately, almost all the risks come back to one thing: you’ll be really, really hungry. “Eating just once a day could very easily create nutritional deficiencies that cause poor immune function, fatigue, irritability, reduced work, school and sport performance and a decrease in bone density (leading to osteoporosis), just to name a few.” says Erica.

It can also set the scene for disordered eating and a poor relationship with food. When we go too long without eating, we will inevitably overeat when we finally get food. This can create really intense feelings of shame and guilt for some. This is not a great dynamic to encourage with food, and can be especially problematic for anyone who has a history of disordered eating. “Those with an eating disorder or history of one, pregnant women, children and adolescents, highly active people and recreational or professional athletes should steer clear,” says Erika. Ultimately, the OMAD diet may offer some immediate results, but is not sustainable long term.