On the other hand, there are some potential benefits to intermittent fasting (IF), and limiting yourself to one meal a day would qualify as such. "The OMAD diet seems to be intermittent fasting to the extreme, where you fast 23 hours [per day] and eat one hour," says Dana Hunnes, PhD, MPH, RD, senior dietitian at UCLA Medical Center. "The argument for it is that you will be eating fewer calories over the course of a day...and that you would dip into your fat reserves for energy utilization—meaning you’ll preferentially burn fat over carbohydrates."
As with other types of intermittent fasting, Hunnes says the main potential benefit to this diet is weight management. "Research shows that restricting eating to a smaller time window than the average American currently eats within may provide benefits for [healthy weight management], metabolic risk factor reduction, and chronic disease prevention," adds Whitney English, RD.
What's intermittent fasting, exactly? Here's the low-down from an RD:
With that said, English offers the first of several caveats to the OMAD diet. "The research in humans is limited, however, and there have been no studies on the OMAD model so we're not able to say if these [intermittent fasting] benefits would extend to a single meal eating pattern," she says. So take everyone hyping it up on Reddit with a very, very hefty grain of salt.
Hunnes also thinks it might be difficult for most people to wait 23 hours between meals. "It also potentially would be more likely to lead to disordered eating patterns whereby you don’t eat for 23 hours and then you either cram in too many calories in that one hour of highly calorically dense foods or conversely, you might be more likely to eat insufficiently and develop somewhat of a [disordered] mindset where you cut more and more calories from the diet," she says.
Experts have also previously warned that intermittent fasting could affect fertility. "The female pituitary gland can sense calorie intake. Below a certain level, it can create a signal from the brain for ovulation to be reduced or absent," Aaron Styer, MD, a reproductive endocrinologist, previously told Well+Good. With an extremely restrictive type of intermittent fasting like OMAD, that risk could be exacerbated. "It could also potentially affect metabolism and normal functioning if you are only eating one time per day," adds Hunnes.
"[The OMAD diet] is unsustainable for the majority of people. Without clinical trials supporting its benefits, it's just another fad." —Whitney English, RD
For these reasons, neither English nor Hunnes recommend this eating plan. "It is unsustainable for the majority of people," says English. "Without clinical trials supporting its benefit, it's just another fad." They both specifically caution against OMAD for certain populations, including people with a history of eating disorders, athletes, patients with diabetes, pregnant and breastfeeding women, and anyone with a thyroid condition.
Instead, Hunnes suggests that people who are interested in intermittent fasting consider the 16:8 diet, where you eat your day's meals within an eight-hour period. "There seem to be more benefits associated with the 16:8 than the 23:1," she explains. English, meanwhile, offers an even more forgiving schedule. "I'm a big fan of what I call 'common sense intermittent fasting', aka ending eating after dinner when it gets dark out and starting again in the morning at breakfast, ideally with a 12-14 hour fasting window," she says. As with any eating plan that's potentially restrictive, talk it through with your doc or an RD to make sure that it's right for your unique health needs.
Long story short, fad diets that sound like a punishment probably aren't worth it. In the case of the OMAD diet, experts generally recommend giving it a hard pass. Here's to three square meals a day still being in.
If it ain't broke, don't fix it—paleo may not trendy, but it's still a hero of the wellness world. Or you could always go Mediterranean—just don't make this one common mistake if you do.
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