Is OMAD an Eating Disorder?

Is OMAD an Eating Disorder?

Is OMAD an Eating Disorder?

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Key Takeaways

  • “One meal a day” or OMAD is a fasting diet that involves eating all your calories in a single meal and fasting for the remaining 23 hours. 
  • While OMAD is not considered an eating disorder, it can increase your risk of developing an eating disorder.
  • Following a fasting diet like OMAD can lead to symptoms of fatigue, poor concentration, and digestive upset. It can also make it hard to meet your nutrition needs.

The current USDA dietary guidelines recommend people follow an eating pattern consisting of three meals per day with snacks in between. However, fasting diets like intermittent fasting and time-restricted eating have grown in popularity in recent years. 

Fasting is defined as a period of time in which a person does not consume calories from food or drinks. Though research is growing on the benefits of fasting diets, these approaches to eatings are not always sustainable and can come with risks

OMAD is an extreme form of time-restricted eating that promotes eating one large meal per day followed by a 23-hour fast. Keep reading to learn more about OMAD and why it may not contribute to a healthy eating pattern. 

What is OMAD?

The OMAD or “one meal a day” approach encourages a person to eat their daily calories from one meal, and no foods are restricted. During the fasting window each day, only zero-calorie fluids are allowed, like water and unflavored tea and coffee.

There are limited human studies on the OMAD eating pattern. An old 2007 study found that people who ate one meal per day versus three meals per day lost more weight during the eight-week intervention. However, the weight loss was not maintained by the six-month follow-up. Blood pressure and cholesterol levels increased in the OMAD group, and subjects reported significantly more hunger. 

Is it an Eating Disorder?

While OMAD is not classified as an eating disorder in the DSM-V, the Diagnostic and Statistical Manual of Mental Disorders, it does have characteristics of disordered eating habits. 

Eating one large meal per day could classify as binge eating in some cases, particularly if it involves a larger-than-normal amount of food, feeling a lack of control, intense guilt and shame, and eating quickly. OMAD also involves extreme restriction for 23 hours per day, which could be a symptom of anorexia or bulimia.

If you’re unsure whether you have an eating disorder, it is important to seek a medical evaluation. To help address your eating concerns, consider scheduling an appointment with a registered dietitian with Nourish for an insurance-covered virtual consult. 

Is OMAD Different Than Fasting?

Since OMAD is a form of time-restricted eating, it is considered a fasting diet. There are numerous forms of fasting that people participate in for reasons from religious beliefs to weight loss.  

OMAD vs. Other Fasting Methods

Time-restricted eating, intermittent fasting, and fasting-mimicking diets are all examples of common fasting methods used for weight loss. Nourish does not condone following these diets. The information below is for your educational benefit. We recommend you work with a dietitian and build a sustainable plan for eating and health management. 

Time-Restricted Eating

Time-restricted eating (TRE) covers various eating patterns, including OMAD. It involves a certain number of hours spent fasting versus eating each day. For example, a 16:8 diet is when a person fasts for 16 hours overnight and eats their meals across a period of 8 hours during the day. 

OMAD follows a 23:1 pattern and is much more restrictive than most TRE diets in the research. Short-term studies (less than one year) show that TRE results in weight loss and improved cardiovascular and metabolic risk factors. However, long-term randomized controlled trials are needed to identify the sustainability of these changes. 

Intermittent Fasting

Another popular fasting diet is intermittent fasting (IF), which also has many variations. Alternate day fasting is when a person eats between zero and 25% of their calorie needs every other day depending on the plan. On the off days, food intake is not restricted. 

Another popular variant of IF is the 5:2 diet, in which a person eats an unrestricted diet five days a week and consumes little to no calories for the remaining two days. 

Numerous studies comparing IF with daily caloric restriction diets show that similar weight loss is achieved between the two eating patterns, showing that one is not superior to the other. Daily caloric restriction means following a reduced-calorie diet every day rather than following prescribed fasting windows or days. 

Fasting-Mimicking Diet

The fasting-mimicking diet involves fasting for at least two consecutive days, where only water or very low-calorie foods are consumed. The person then returns to an unrestricted diet for at least one week. The cycle is then repeated at different time intervals ranging from every few weeks to every few months.

Since this involves multiple days of fasting in a row, it comes with significant health risks, like losing weight too quickly or experiencing rapid blood sugar or blood pressure drops. 

Why OMAD Isn’t Healthy or Sustainable

A study on time-restricted eating found that participants felt the diet was challenging to follow, and more than half did not think they could continue the eating pattern in the long term. In addition, the majority of studies done on restrictive diets have found that they do not result in sustainable weight loss in the long term.

OMAD is not sustainable for many. It also comes with some risks, like feeling poorly, not meeting nutritional needs, and an increased risk for eating disorders and metabolic dysfunction.

Possible Negative Symptoms

When you go long periods of time without eating, you can experience adverse symptoms like intense hunger, fatigue, difficulty concentrating, dizziness, and lightheadedness. These are due to drops in blood sugar related to a lack of consistent energy from food. 

Fasting diets are not recommended for people with diabetes because of the risk of hypoglycemia, a dangerously low blood sugar level, from not eating regularly. 

In addition, eating one large meal per day can lead to digestive symptoms due to the volume of food. These include acid reflux, digestive upset, and bloating. 

Inadequate Nutrition:

When you only eat one meal per day, it can be challenging to meet all your daily nutrition needs, like protein, fiber, vitamins, and minerals. For example, skipping breakfast, which is common in many fasting diets, is associated with an inadequate dietary fiber intake. 

Disordered Eating

OMAD is a restrictive fasting diet that involves skipping meals. Research shows that people who routinely skip meals have a higher risk of developing an eating disorder. Further, restrictive eating is associated with having an unhealthy relationship with food, a common characteristic of many eating disorders. 

Metabolic Effects

Despite promising research on the potential metabolic benefits of fasting diets, such as reduced insulin levels, there can also be adverse metabolic effects. Research shows that people with irregular meal habits have an increased risk of metabolic syndrome. Specifically, skipping breakfast has been linked to higher mortality rates from cardiovascular disease. 


Many people find it difficult to adhere to fasting diet plans, and long-term studies on the sustainability and metabolic impacts of these diets are needed. 

OMAD is an extreme form of time-restricted eating that has minimal evidence to support it. Caution should be taken when considering this type of plan, especially for individuals with a history of eating disorders or diabetes. 

Seeking Help from a Dietitian

If you want to learn more about healthy eating, consider eating disorder nutrition therapy through Nourish. Visits are 100% virtual and covered by insurance.

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