Intermittent fasting goes extreme with the "One Meal a Day" diet. Here's why one registered dietitian says it's a dangerous approach.
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At the start of every year, a new diet usually spikes on the ol' Google search, and inevitably some of my clients come in asking about it. Last year, intermittent fasting was all the rage. While I don't think it's for everyone (particularly current or former disordered eaters), I am a fan of intermittent fasting. Limiting your eating hours a bit can let your body stop focusing on digesting and instead spend some time on de-stressing, anti-inflammation, memory, immunity, and so much more.
But it's never a surprise to me when a good thing goes extreme. And then goes bad. That's the case of OMAD—the new diet that's seen a surge in popularity.
What Is the OMAD or "One Meal a Day" Diet?
The One Meal a Day (OMAD) diet, essentially takes intermittent fasting (IF) to the highest level. The type of IF I support and find beneficial is generally called 14:10 or 16:8 (14 to 16 hours without food, 8 to 10 hours of eating three regular meals). OMAD recommends 23:1—that's 23 hours of fasting, and one hour of eating per day. (Related: Everything You Need to Know About Intermittent Fasting)
Essentially, you can eat whatever you want during your one hour of eating. This diet is far more focused on when you're eating than what you're eating (which, as a dietitian, is one of my 100 concerns with OMAD).
There are 4 rules of OMAD:
- Eat one meal per day.
- Eat around the same time daily (within a one-hour window).
- Eat off one single plate, no going back for seconds or thirds.
- Your meal should only be 3 inches high (which I guess means you have to bring a ruler to lunch?).
This may sound outrageous—I hope it does—but the OMAD diet is gaining popularity because some celebrities and athletes (MMA fighter Ronda Rousey, for example) have talked about following it recently. And well, you know how these things catch Insta-wildfire!
There are claims that one meal a day means "deeper" benefits than are seen with standard intermittent fasting, including decreased inflammation and disease risk, and increased cellular turnover. However, there is no research yet to validate these statements. And in fact, the risks are much greater than any potential benefits.
The Risks of OMAD
When you go longer than 14 to 16 hours food-free, you run the risk of many biological issues. The first of these biological issues is, of course, being absolutely ravenous. You've probably joked about being "hangry," but the reality is that this type of restrictive eating doesn't just make you cranky. When you haven't eaten in almost a day, your body enters starvation mode. This can wreak havoc on your energy and on your metabolism (the opposite effect for anyone with a weight loss or maintenance goal in mind.)
It's also pretty much impossible to get all the nutrients you need from one meal a day, even if it's a super-healthy meal. A truly nutritious diet is about full body nourishment. It's meant to get you through your workout or work day with power and focus. I'd say this is close to impossible with OMAD.
OMAD-style dieting can also lead to serious binge eating in that one hour a day and can easily turn into "cheat day" style eating—one hour of eating whatever you want because you've deprived yourself for 23 hours. While there's a psychological component to this, it's also physiological: If you're entering a meal with low blood sugar, your body craves fast-absorbing calories, like sugar or white carbs. Eating all your food for the day in one hour can also cause serious digestive distress. (Related: How to Tell When Binge Eating Gets Out of Control)
Even more importantly, for women, hormones are extremely sensitive to blood sugar. When blood sugar dips, cortisol and other stress hormones are impacted. And when your hormones go haywire, your mood, period cycle, metabolism, and weight can all be impacted. Following OMAD will result in blood sugar fluctuations and leave you more likely to binge, followed by long-term metabolic and hormonal disruption.
All women's bodies are different—and I don't even recommend 16:8 intermittent fasting for everyone because of it. (Related: What Fit Women Need to Know About Intermittent Fasting) For example, some are much more sensitive to these longer food-free mini fasts than others. Some women need to eat first thing in the morning, while some women can wait until after a workout. Rather than listening to what you need as an individual, this diet means totally ignoring your body's individual nutritional needs, hunger cues, and daily life fluctuations (like hello, going to brunch or dinner with friends!), and blindly eating at the same time every day.
The Bottom Line
While I am generally in favor of a little self-experimentation, OMAD is just an OMG no for me. Thank u, next!