The great ‘one meal a day’ myth: Why the celebrity OMAD diet is no weight loss miracle

Is restricting yourself to just one meal a day the secret to staying trim or is it just restrictive eating?

By Dr Emma Beckett

Published: Thursday, 25 May 2023 at 12:00 am

Society has an ongoing fascination with the constantly shifting trends in celebrity diets. The one meal a day (or OMAD) diet is one such trend, reportedly championed by the likes of Bruce Springsteen, Coldplay frontman Chris Martin, football pundit Gary Lineker and even Rishi Sunak, the prime minister. But does the science back up the claims?

OMAD is an extreme fasting diet. As the name suggests, it involves eating just one big meal a day, with fasting or very minimal eating in between. The key focus of this kind of diet is weight control and simplicity.

There are many celebrity anecdotes surrounding OMAD and from an evolutionary point of view, it can seem reasonable to suggest that human biology is better suited to less frequent meals. This theory is based on our ancestors often experiencing cycles of feasting and fasting rather than the relatively modern construct of three meals a day.

But while fasting itself isn’t new, the research on its health impacts is still in its infancy and there are very few studies on OMAD and the evidence supporting other more periodic types of fasting can’t necessarily be extrapolated into extreme fasting.

One trial exists on OMAD, where participants ate only one meal a day, or three meals per day, with their calorie intakes tailored to theoretically maintain their current weight.

When on one meal per day they reduced body weight and fat levels, and displayed features of “metabolic flexibility” (changes in measures of how fats and carbohydrates are metabolised). But participants also experienced a loss of muscle and bone mass. This highlights that a focus on weight loss alone can miss the potential downsides of this kind of diet.

Importantly, the results of this study can’t be applied to everyone. Only relatively healthy people were included and no one with obesity, cardiovascular disease, diabetes, mental disorders, eating disorders or other metabolic conditions was allowed to participate.

Furthermore, the trial was small and short, with just 11 participants following the diet for 11 days.

Read more:

What are the risks associated with the OMAD diet?

One of the claims made by supporters of OMAD and other fasting diets is that you can eat whatever you want for the one meal you are eating each day. But if all nutrients for good health are to be obtained in just one meal, it needs to be nutrient dense and balanced to ensure you get a sufficient intake of fibre, protein, vitamins and minerals.

Supplements may help avoid nutritional deficits but they lack the complexity of foods, which means other healthy essentials, such as bioactive compounds, may be missed. This means there may be longer-term consequences for bone, digestive and other elements of your health, despite the easy-to-measure and instantly gratifying weight loss.

Indeed, when meal frequency has been studied in larger groups (over 24,000 people) for longer periods (about 15 years), eating just one meal a day was linked to a higher risk of death from any cause, and from cardiovascular diseases.

Observational studies like this can’t show the cause of the relationship, but the results were found even when factors like age, gender, race, ethnicity, education, income, smoking, alcohol intake, physical activity, energy intake, food insecurity, snacking habits and health at the start of the study were taken into account.