Short for "One Meal a Day," the OMAD diet is exactly what it sounds like — eat whatever your heart desires for just one meal, then avoid consuming food and drinks with calories for the rest of the day. The goal? Weight loss.
That one allotted meal comes without restriction. It can be pizza and ice cream washed down with soda, or a piece of chicken with a side of veggies and roasted potatoes and a glass of water. You can also enjoy your meal any time of day — morning, noon or night — although Logan Wolf, author of One Meal a Day Intermittent Fasting, recommends eating your meal in the evening.
The thinking is that by limiting yourself to just one "feeding" per day, you're reducing your overall caloric intake across a 24-hour period, thus losing weight without having to cut out certain food groups, or tracking macros or calories like many other weight-loss diets.
The big questions: Does the OMAD diet work, and is it safe? We took a closer look at this latest fasting diet trend and had Bonnie Taub-Dix, RDN, author of Read It Before You Eat It — Taking You from Label to Table, weigh in.
How Is the OMAD Diet Different From Other Types of Fasting?
Fasting has been around for thousands of years, but intermittent fasting has grown in popularity over the past few, including its variety of options. Here's a breakdown of the different types of intermittent fasting and how they're different from the OMAD Diet:
- 16:8 method: This intermittent fasting structure involves abstaining from food and caloric beverages for 16 hours a day, allowing yourself an eight-hour window to eat and drink as you please. This can be done daily or just a few times a week.
- 5:2 diet: This method involves five days of unrestricted eating in a row followed by two days of restricted calorie intake — just 500 calories a day for women and 600 calories a day for men.
- Complete alternate day fast: This method involves alternating days of complete fasting (drinking just water, tea, black coffee) with days of eating without any restriction.
- Warrior diet: This plan is very similar to the OMAD diet but calls for 20 hours of under-eating followed by four hours of overeating, and there are strict rules around the types of foods you can eat.
Can You Lose Weight on the OMAD Diet?
Anytime you create a calorie deficit — whether it's by cutting down portions, tracking calories, omitting certain food groups or even skipping meals (or days of eating) — you will lose weight. So while yes, you can absolutely lose weight on the OMAD diet, you have to ask yourself some important questions before you try it.
First up: How realistic is it for you to eat only one meal a day? A July 2017 study published in the Journal of the American Medical Association of Internal Medicine compared intermittent fasters to those who just restricted calories over the course of a day, and while both groups lost weight, the dropout rate in the fasting group was significantly higher.
The issue with trying to lose weight isn't a shortage of diets — it's whether or not they're safe, sustainable or even the right approach altogether.
Why the OMAD Diet Isn’t Healthy
1. You’ll Likely Come Up Short on Nutrition
"This OMAD diet is more like an OMG to people that are sensible," says Taub-Dix. "Food types are not limited so chocolate cake lovers can stack a few slices on a plate and voila — you have your food intake for the day!" The problem with this? It's big enjoyment once a day and void of any nutritional value, she adds.
The likelihood of you hitting the nail on the head and getting 100 percent of all of the macro- and micronutrients you need in a day is slim-to-none. Getting enough fiber and protein along with all of the vitamins and minerals would be a serious challenge when following this type of meal pattern over an extended period of time.
2. It Promotes Disordered Eating
Following a diet like the OMAD Diet is problematic because it teaches you to ignore your hunger cues and ultimately, stop listening to your body. When you do eventually return to eating three square meals a day, you might not be able to tell when you're hungry or when you're full.
Also, severe restriction and then gorging yourself on food are signs and symptoms of disordered eating, according to the National Eating Disorder Association. While the OMAD diet doesn't promote binging food, it's likely some could fall into this pattern with the one-hour time frame of food freedom followed by 23 hours of restriction.
3. You Probably Won't Feel Great
"This over- and under-consumption of food throughout the course of the day can have negative consequences," says Taub-Dix. "Skipping meals can cause lightheadedness, erratic blood glucose levels and irritable moods."
Eating too much at one sitting can lead to gastrointestinal problems including acid reflux , bloating, gas, pain and discomfort, according to the U.S. National Library of Medicine.
4. It Can Mess With Your Hormones
A March 2019 study published in Nutrients concluded that excessive calorie restriction can cause some serious issues with our hormones. For men, this might mean a decrease in testosterone and for women, menstrual cycle disorders.
5. The Science Is Minimal
The bottom line is that although there is little to no research on this plan, we can take a guess at just how long-lasting this diet would be for most. If you actually enjoy eating (and we hope you do!), being this regimented and restrictive is a recipe for disaster, says Taub-Dix.
How to Fast Safely
If you've heard about the potential benefits of fasting and are still interested in trying other forms of intermittent fasting aside from the OMAD diet, there are healthier ways to get started.
1. Start Slow
Try a 12 hours on, 12 hours off structure to start and go from there. Easing in and experimenting will let you feel out how the changes really impact your body on a day-to-day basis.
2. Stay Hydrated
It's also important to stay hydrated so drink plenty of water — tea and coffee are OK too. As a general guideline, men require 13 cups of fluid per day to maintain hydration, and women require an average of 9 cups per day, according to a 2016 paper published in the American College of Sports Medicine's ACSM's Health and Fitness Journal.
3. Focus on Quality Foods
Protein and fiber will help with your appetite but eating nutrient-dense foods like lean proteins, whole grains, fruits, vegetables and legumes will ensure you're getting the nutrition you need.
4. Work With a Professional
While fasting has been shown to have some benefits, it comes with health risks and is not for everyone. If you're considering fasting, talk with your doctor or a dietitian to make sure it's appropriate, especially if you have a medical condition.
Women who are trying to get pregnant, women who are pregnant or breastfeeding, children, older adults, people with low blood pressure or low blood sugars, people who are underweight or people with a history of an eating disorder should not try fasting.
Is This an Emergency?
- One Meal a Day Intermittent Fasting: "The Powerful Secret of the OMAD Diet for Extreme Weight Loss"
- Journal of the American Medical Association of Internal Medicine: "Effect of Alternate-Day Fasting onWeight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults"
- National Eating Disorder Association: "Binge Eating Disorder"
- Nutrients: "Intermittent Fasting in Cardiovascular Disorders—An Overview"
- U.S. National Library of Medicine: "Indigestion"
- American College of Sports Medicine's Health and Fitness Journal: "The Hydration Equation: Update on Water Balance and Cognitive Performance"