The OMAD diet, which stands for "one meal a day," is an intermittent fasting diet in which you fast for 23 hours of the day and consume all your daily calories within one hour (which falls within the same four-hour window everyday).
There are no restrictions on how many calories can be eaten during the one-hour meal period.
It's possible to lose weight on the OMAD diet, but experts say the lifestyle isn't sustainable and the diet comes with risks.
What's your favorite meal of the day? Maybe it's breakfast when you can have a hearty plate of eggs and bacon, or dinner when you can finally have that delicious salmon you've been marinating for hours.
Now, imagine that's the only meal you can eat each day. That's the premise behind the OMAD diet, which stands for "one meal a day," which is essentially a form of fasting.
While fasting can feel good for some people (just ask Vanessa Hudgens or Jenna Jameson) and lead to weight loss, some experts believe certain methods of fasting like the OMAD diet aren't a healthy, sustainable solution to drop pounds. Here's everything you need to know about the controversial fasting diet.
What exactly is the OMAD diet?
"Think of OMAD as intermittent fasting on steroids," says Dena Champion, RD, of The Ohio State University Wexner Medical Center. "OMAD is literally when someone eats one meal daily during one hour of the day and then fasts the other 23 hours." You are allowed to drink black coffee or other zero-calorie drinks during that fasting time—but nothing else.
On top of that, you're instructed to eat that one meal during the same four-hour window every day, adds Jen Oikarinen, a clinical dietitian with Banner University Medical Center Phoenix. "Consistency is emphasized in the OMAD diet," she says. And while it is recommended that you make healthy food choices, it's more about when you eat than what you eat, notes Champion.
OMAD dieters are supposed to adhere to a set of rules known as the "four ones rule," says Oikarinen. So if you're on the OMAD diet:
You should only be eating one meal per day
You should only eat within one hour of your four-hour eating window
You must eat off one plate
You should limit yourself to one beverage that contains calories if you want one
Worth noting: While the OMAD diet is technically a fasting diet, it's quite different from other intermittent fasting diets like the 16:8 diet, which instructs you to fast for 16 hours and eat three (or four!) meals during the remaining eight hours.
What should you eat on the OMAD diet?
Though there are rules for when and how to plate your meal, the OMAD diet doesn't restrict how many calories you can eat during your eating window. If you're curious what an OMAD meal looks like, here's a breakdown of what someone might eat, from Nicole Short, RDN and nutritionist Lisa Richards, based on whether the eating window is closer to breakfast or dinner.
These meals aren't recommendations, but examples of what eating on the OMAD diet might look like. Clearly, you'd have to consume a lot at once in order to get close to meeting your caloric needs for the day.
OMAD breakfast option one:
1 cup oatmeal (Quaker, Multigrain Instant) = 267 cal
1/4 cup walnuts = 190 cal
1 Tbsp flaxseed = 35 cal
1/2 cup 2% milk = 60 cal
2 turkey sausage links = 132 cal
1/2 cup strawberries = 35 cal
1 cup orange juice = 122 cal
2 large poached eggs = 143 cal
1.5 cup kale = 49 cal
1 Tbsp olive oil = 120 cal
2 Tbsp parmesan cheese = 78 cal
Total = 1,232 cal
OMAD dinner option one:
3 oz grilled salmon = 120 cal
1 cup roasted Brussels sprouts = 36 cal
1/2 cup quinoa = 262 cal
1 Tbsp olive oil = 120 cal
1 slice chopped bacon = 224 cal
1/2 cup rice pudding w/ 2% milk = 142 cal
1 cup steamed baby carrots = 51 cal
1 small apple = 100 cal
Almond butter = 200 cal
Total = 1,255 cal
OMAD breakfast option two:
2 egg omelet = 140 cal
¼ cup shredded cheese = 110 cal
1/2 cup strawberries = 25 cal
2 slice whole wheat toast = 240 cal
¼ cup bell peppers = 10 cal
1 spinach tortilla wrap = 130 cal
½ cup tomatoes = 30 cal
½ avocado = 150 cal
½ cup cooked spinach = 10 cal
½ cup black beans = 120 cal
1 cup cooked steel oatmeal = 160 cal
1/2 skim milk = 50 cal
2 Tbsp peanut butter = 150 cals
1 banana = 120 cal
1 tablespoon chia seeds = 55 cal
Total = 1,500 cal
OMAD dinner option two:
1 cup lentil soup = 190 cal
½ cup whole grain spaghetti = 160 cal
½ cup mushrooms = 20 cal
1 /2 cup marinara sauce = 70 cal
¼ cup parmesan cheese = 85 cal
3 oz skinless baked chicken = 220 cal
1/2 cup farro = 170 cal
1 cup broccoli = 60 cal
Turkey burger on a whole grain bun = 360 cal
1 cup shredded lettuce = 7 cal
½ cup tomatoes = 30 cal
1 baked sweet potato = 112 cal
½ cup asparagus = 16 cal
Total = 1,500 cal
What are the pros and cons of the OMAD diet?
Since the OMAD diet is a form of intermittent fasting, you may experience some of the pros of intermittent fasting diets in general. Intermittent fasting has been linked to weight loss, especially when you have an earlier eating window, before 3:00 p.m. Other benefits of intermittent fasting that you may experience include clearer skin, reduced inflammation, and better sleep. Some dieters have even been able to achieve dramatic transformations by adopting a lifestyle based on intermittent fasting.
One benefit of this diet is that it's efficient for people who are on the go and do not care to prepare three to four meals a day, says Short. On the other hand, Short also points out there's major risks involved in this diet. Adopting the OMAD way of eating can result in unstable sugar levels, which can lead to other problems like fatigue, headaches, and unintentionally putting your body into ketosis (this is when your body starts to burn fat instead of carbs for fuel, which can come with it's own potential health issues).
One study published in the Journal of Nutrition Reviews also noted that the type of intermittent fasting required to follow the OMAD diet provides such a short eating window that it may make it hard to eat enough calories to make up for the deficit of calories achieved during fasting. Short adds that if your one meal isn't nutrient dense, it's likely you may develop nutritional deficiencies too.
A fasting program like OMAD can also result in mood swings, muscle loss, hormone disturbances, and even changes in your menstrual cycle (like having it stop completely), says Oikarinen.
So, can the OMAD diet help me lose weight?
Yes, but again, some experts say it's neither healthy nor sustainable weight loss.
OMAD is basically a starvation diet, if you follow all the stipulations, says Rebecca Elbaum, RD, clinical administrative dietitian at Montefiore Medical Center in New York. That's because you're not consuming enough calories with just one meal as you would by eating eating three or four times a day, so weight loss will occur.
Should I try the OMAD diet?
While plenty of people sing the OMAD diet’s praises online, and some experts certainly endorse various forms of intermittent fasting, Elbaum believes not even healthy people should try the OMAD diet. And that goes doubly for anyone who's pregnant, breastfeeding, recovering from past disordered eating, has diabetes, or even regularly exercises or lifts weights, she says.
"Healthy weight loss will be whatever is the most sustainable over a lifetime," she says. "This includes a healthy, balanced diet and regular exercise."
Certain populations like the elderly, children, and people with health conditions or who take medication should steer clear of the OMAD diet too, as not getting a regular intake of calories can cause serious health complications.
If you are interested in some type of fasting, a less intense form (like the 16:8 diet) might be your best bet—but even then, it's wise to talk to an RD about your options and how best to work an intermittent fasting diet into your lifestyle, says Oikarinen.
The bottom line: Most experts agree to steer clear of the OMAD diet—it won't promote healthy or sustainable weight loss.
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