OMAD: One Meal a Day Fasting
A Weight Loss Kickstart Or Passing Fad?
The search continues for the optimal way to eat for weight management and health. Is One Meal a Day fasting (OMAD) the answer to that quest or unnecessary torture?
Let’s cover OMAD fasting, discuss any benefits, and see what the research says.
What is OMAD fasting?
One meal is eaten daily, typically in the evening.
OMAD fasting is an emerging trend in the fitness world and is gaining traction elsewhere because of its simplicity.
Supporters say OMAD promotes weight loss and has other health benefits. But is it worth being hungry all day? And is it healthy to only eat one meal a day? OMAD is not for everyone. Here’s what you should know before trying an OMAD fast.
The “Fasting Window.”
A fasting window is a time in the day when no calories are eaten.
There is a “fasting window” for any fasting plan. OMAD fasting is the most extreme version of intermittent fasting. Eating occurs only 1 hour out of the day, i.e., 23 hours with no calories. This is also known as 23:1 fasting. There are no specific recommendations for what food is eaten during the hour.
OMAD fasting is done daily by some people; others may do it a few times a week. Many people use it to help weight loss plateaus, times when their weight loss regiment hits a period that no further weight loss occurs.
OMAD is less commonly used compared to other forms of Intermittent fasting. The more typical types of intermittent fasting allow two or three meals during a 24 hour period. There are several forms of Intermittent fasting, each with different fasting windows. The 16:8 protocol is most commonly used, with sixteen hours of fasting and an 8 hour period where food is consumed.
Benefits of OMAD fasting
Benefits of OMAD fasting include less time for meal preparation and less money spent on food.
It is difficult to eat as much in your 1-hour window compared to eating throughout the day. Less food = less expense and, with only eating one hour of the day, meal prep time is drastically reduced.
OMAD & Weight Loss
Does it help people lose more weight?
The effect of meal frequency on weight has been studied, and the body of research is growing. (1). One study looking at meal frequency found that eating only 1 or 2 meals per day was associated with decreased BMI ( body mass index) compared to eating three or more meals per day. A lower BMI* is typically good and indicates a healthy weight.
This same study also looked at meal timing and found that people eating their largest meal at breakfast had a drop in BMI than those eating their largest meal at lunch or dinner (2).
Fewer meals earlier in the day meant more weight loss in this study. So, eating one meal in the evening, as most people do on an OMAD diet, may or may not be beneficial.
Another factor to consider is the regularity of a person’s daily eating. Does the “eating window” time occur at a similar time each day, or is it unpredictable? One study compared the number of meals eaten in a day and whether the meals were eaten at the same time each day or at various times. People who ate in a predictable pattern consumed fewer calories, regardless of how many meals were eaten (3). Eating meals at predictable times was beneficial for weight maintenance (4).
While studies on intermittent fasting and weight loss show benefit, there is currently no research looking specifically at OMAD and weight loss.
*BMI 18-25 is ideal. Typically, below 18 is underweight, over 25 is considered overweight.
Is OMAD Better Than Other Forms Of Fasting?
There is a rapidly growing amount of research on the benefits of fasting, but none explicitly compares one meal a day fasting to other forms.
Risks of OMAD
Nutritional deficiencies With limited food intake, the risk of nutrient deficiencies is high.
Exercise While exercise during fasting can be done, heavy training during prolonged fasting may lead to muscle breakdown.
An unhappy stomach Some people experience cramping or stomach pain with eating after prolonged periods of fasting. Others may have diarrhea or loose stools.
Increased blood sugar OMAD fasting has been found by one study to increase fasting glucose (5). This is in direct contrast to intermittent fasting, which has been found to improve fasting glucose (6).
Medication concerns. Some medications need to be taken with food. If they are taken several times a day, this is not possible with OMAD.
Social isolation It is challenging and socially isolating to follow a plan where you can no longer share most meals, happy hours, or birthday parties eating with friends and family.
Who should not try OMAD fasting?
- Elderly people
- Pregnant women
- Anyone with a history of disordered eating
- Underweight individuals
Key takeaways: OMAD Fasting
OMAD may help some people lose weight, but it is not without risk, and specific populations should avoid it altogether.
There are many benefits to intermittent fasting, but it isn’t the right fit for some people, and the research on OMAD specifically is scant.
Even if you don’t fall into one of the categories that should never try OMAD, it may not be for you. If you experience persistent symptoms such as dizziness, headaches, fatigue, and nausea, skip OMAD.
Perhaps the most significant takeaway from these questions about OMAD is the importance of personalized recommendations. We all have different genetics, lifestyles, and goals; nutrition recommendations need to be personalized and evidence-based. There is more than one “right” way to eat!
Related Fasting Research
THIS ARTICLE IS COPYRIGHTED BY AMY BURKHART, MD, RD.
Dr. Amy Burkhart is a doctor (M.D.), Registered Dietitian, R.D., She specializes in gut health, and is one of only two integrative MDs in the US who is also a dietitian. She is a specialist in celiac disease and gluten/wheat-related disorders. Follow her on Facebook at Amy Burkhart MD RD or on Instagram @TheCeliacMD