Obesity expert explains the OMAD diet – it works and it’s safe

What do British Prime Minister Rishi Sunak and singer Bruce Springsteen have in common? They are part of a growing group of public figures extolling the benefits of eating just one meal a day, writes Nick Fuller of the University of Sydney.

As a result, the one-meal-a-day diet (OMAD) is the latest weight loss trend to gain attention. Advocates claim it leads to rapid and long-term success in weight loss and better health, including delaying the aging process. Like most weight loss programs, the OMAD diet makes big, bold promises. Here’s what you need to know about eating one meal a day and what it means for weight loss.

Essentially, the OMAD diet is a type of intermittent fasting where you fast for 23 hours and consume all your daily calories in one meal eaten within an hour.

The rules of the OMAD diet are presented as simple and easy to follow:

1. You can eat whatever you want as long as it fits on a standard plate, with no calorie restrictions or nutritional guidelines to follow.

2. You can drink calorie-free drinks throughout the day (water, black tea and coffee).

3. You should follow a consistent meal schedule, eating your only meal at about the same time each day.

In addition to creating a calorie deficit, which leads to weight loss, proponents believe that the extended fasting period of the OMAD diet leads to physiological changes in the body that promote better health, including boosting metabolism by triggering a process called ketosis, in which your body burns stored fat for energy instead of glucose.

Unfortunately, research on the OMAD diet is limited. Most studies examined its impact on animals, and the main human study involved 11 lean young men who followed the OMAD diet for just 11 days.

Claims about the OMAD diet are usually based on research on intermittent fasting rather than the OMAD diet itself. There is evidence to support the effectiveness of intermittent fasting to achieve weight loss. However, most studies have only focused on short-term outcomes, usually looking at outcomes over 12 weeks or less.

A longer-term study in 2022 randomly assigned 139 obese patients to either a calorie-restricted diet with time-restricted eating between 8:00 a.m. and 4:00 p.m. or a daily calorie-restricted diet. for 12 months.

After 12 months, both groups lost about the same weight and experienced similar changes in body fat, blood sugar, cholesterol and blood pressure. This indicates that long-term weight loss achieved with intermittent fasting is not superior and equal to that achieved through traditional dietary approaches (daily caloric restriction).

What are the problems with the OMAD diet?

1. It can cause nutritional deficiencies and health problems.

The OMAD diet’s lack of nutritional guidance on what to eat for that meal a day raises many red flags.

The meals we eat each day should include a balanced source of protein with whole carbohydrates, vegetables, fruits, protein and good fats to support optimal health, disease prevention and weight management.

Failure to eat a balanced diet will lead to nutritional deficiencies that can lead to poor immune function, fatigue and decreased bone density leading to osteoporosis.

Fasting for 23 hours a day can also lead to extreme feelings of hunger and uncontrollable cravings, which can mean you’re constantly eating foods that aren’t good for you when it’s time to eat.

2. It is unlikely to be sustainable.

You may be able to stick with the OMAD diet initially, but it will wear off over time.

Extreme diets – especially those that prescribe extended periods of fasting – are not enjoyable, leading to feelings of deprivation and social isolation during mealtimes. It’s hard enough to turn down a piece of birthday cake from the office at the best of times, imagine how that would feel when you haven’t eaten in 23 hours!

Restrictive eating can also lead to an unhealthy relationship with food, making it even more difficult to reach and maintain a healthy weight.

3. Quick fixes don’t work.

Like other popular intermittent fasting methods, the OMAD diet appeals because it’s easy to digest and results quickly.

But the OMAD diet is just another fancy way to cut calories to get some quick weight loss.

As your weight drops, things will go downhill fast as your body activates its defense mechanisms to defend your weight loss. In fact, it will regain weight—a response that stems from the need of our hunter-gatherer ancestors to survive periods of deprivation when food was scarce.

Despite the hype, the OMAD diet is unsustainable and does not result in better weight loss results than its predecessors. Our old habits creep in again and we find ourselves fighting a cascade of physiological changes to ensure we regain the weight we lost.

Successful long-term weight loss comes down to:

• losing weight in small chunks that you can sustain, especially periods of weight loss followed by periods of weight maintenance and so on until you reach your desired weight

• making gradual changes in your lifestyle to ensure that you create habits that last a lifetime.

This article was written for The Conversation by Nick Fuller, Research Program Leader of the Charles Perkins Centre, University of Sydney.