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Have you tried OMAD diet?

Analysis by Dr. Joseph Mercola Fact Checked

Story at-a-glance -

  • OMAD diet, the acronym for “one meal a day,” involves eating all your nutrients in a one-hour time slot, with nothing else on the menu, other than calorie-free beverage options, for the remaining 23 hours per day
  • Proponents of the OMAD method of eating say it’s a quick way to lose pounds, and one of the benefits is that it’s convenient, but one rule is to limit your fasts; extended fasts aren’t recommended
  • Three videos on the topic explain OMAD; compare the merits of OMAD, intermittent fasting and the warrior diet; and offer tips on how to make it work
  • Foods to avoid on OMAD include trans fats, processed foods, processed sugar and foods that contain lectins and liquid calories, while suggested foods are organic, pastured eggs and grass fed meats, vegetables and fermented foods
  • Overall benefits of fasting include lowered blood sugar, lower weight, improved heart health, better sleep and better memory

You don’t have to look far to find options for eating — aka “diets” — designed to help you lose weight, build muscle or otherwise optimize your health. There’s the keto diet, which focuses on burning fat for fuel, the paleo diet, aimed at consuming what our hunter-gatherer ancestors may have eaten, gluten-free and vegetarian/vegan modes of eating, just to name a few.

Now there’s the OMAD diet, the acronym for “one meal a day.” It’s been called an extreme form of intermittent fasting (or 16/8), and involves eating all your nutrients in a one-hour time slot on a daily basis, with nothing else on the menu for the remaining 23 hours other than calorie-free beverage options. Another way it’s referred to is the 23/1 diet.

The premise is that you’ll end up eating less, but proponents, like Estonian-born Siim Land, a high performance coach who’s gained attention on the internet with OMAD advice and recommendations, says weight drops off quicker, and you feel more satiated eating a smaller number of calories.

As a writer, blogger, life coach, social media personality and entrepreneur, Land says his goal is to create more content about optimizing “physiology, mindset and performance — a lot of biohacking, self-improvement and other lifehack types of stuff.”1 He asserts there’s much about fasting that is misunderstood, which makes some people dismiss the concept as simple starvation. He makes two points:

“Starvation is a severe deficiency in energy intake. The body doesn’t have access to essential nutrients and is slowly wasting away by cannibalizing its vital organs. Fasting is a state of metabolic suspension in which you’re not consuming any calories. Despite that, your body is still nourished and gets the energy it needs.”

He recommends a one- to five-day fast or calorie restriction, which will have beneficial rather than detrimental effects. This is because unless someone is severely underweight, most people have enough stored energy to sustain them, and it in fact increases your metabolic rate by 14%.2

OMAD diet: Experts have their say

If you’ve ever found yourself missing a meal or two due to unforeseen circumstances, you may have noticed your functions, both physically and mentally, weren’t firing on all cylinders. It’s been called “hangry,” something we all have experienced.

While Land lists the potential benefits of an OMAD diet, beginning with rapid weight loss, scientific studies on the 23/1 method are very limited, and there are skeptics. According to Refinery29, “This (OMAD) pattern — along with the stringent rules around when you can and can’t eat — could easily harm your relationship to food and eating in the (long term).”3 Further:

“Although you’re technically ‘allowed to’ eat whatever you want during this one meal, you’re still eating way fewer calories (which are units of energy) than you would typically need in a day …

People claim the OMAD diet speeds up weight loss, and is extremely convenient — especially in the summertime when you’re traveling a lot. But, like many internet-famous diet trends, this should come with a massive disclaimer that it's not for everyone, and probably will do more harm than good.”4

Registered dietician, nutritionist and holistic health counselor Robin Foroutan says the OMAD approach is unnecessarily restrictive. She believes a single enormous meal in one sitting can have dire effects on proper digestion and absorption, plus fasting all day long and suppressing intense hunger makes it even more difficult to make healthy food choices. I also believe that timing of when you do all that eating is important, as you certainly don’t want to eat within three hours of bedtime.

SELF5 interviewed Brigitte Zeitlin, a certified nutritionist and registered dietitian, who observed, “Eating regularly throughout the day prevents dips in your energy, keeps you alert and focused.”

Zeitlin adds that without a frequent carb supply, your blood sugar can dip too low, leaving you feeling sluggish, irritated, and feeling like you can’t concentrate. “You are likely to overeat to make up for the lack of calories you took in throughout the day. That can cause nausea, constipation, bloating and exhaustion.”

Medical News Today6 notes that one reason OMAD is so popular is that you don’t need “cheat days” because nothing’s off the table, per se, and counting calories is unnecessary. However, some information from nutritionists and medical experts regarding both intermittent fasting and the OMAD in particular is erroneous,7 which muddies the waters.

Land, whom I plan to interview for an article soon, has studied this in detail, and he says he’s trying to clear that up. HIs book, “Metabolic Autophagy,” covers such topics as intermittent fasting, the OMAD diet and promoting longevity.

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What to eat and not to eat on the OMAD diet

Looking at the body’s anabolic-catabolic cycles of nutrition and exercise, Land says, in theory, you could get away with eating junk food and still be healthy because the long period of fasting is a “huge buffering agent.” But, “If you want to lose fat, then eat about 500 to 600 calorie deficit. To gain weight, eat about 300 to 500 extra calories.”8

For people who have no specific physique goals, Land believes percentages of calorie distribution on the OMAD diet could loosely follow his model of 25% to 35% from protein, 40% to 50% from fat, and 10% to 20% from carbs.9 Foods to avoid are:

  • Inflammatory foods such as grains, processed meats such as hot dogs, trans fats and sugar
  • Allergenic foods that contain lectins, such as tomatoes, beans and bell peppers; also gluten and soy
  • Liquid calories, including soda, juice and alcoholic beverages
  • Foods that cause constipation or bloating, including cheese, dairy, beans, grains and legumes

Foods that would be acceptable and even desirable on the OMAD plan include:

  • “Whole food complete proteins,” as they come with all the essential nutrients you need, such as vitamins, minerals, amino acids and fatty acids, as well as organic, pastured eggs, fish, chicken and organic, grass fed meats, including organ meats
  • Healthy vegetables and fermented foods to improve your gut health and get 20 to 30 grams of fiber per day, such as sauerkraut and kombucha
  • Herbs and spices, especially thyme, dill, fennel seeds, rosemary, coriander and arugula
  • Healthy fats which include olive oil, coconut oil, avocados, wild-caught Alaskan salmon, nuts and seeds

Advantages and risks of fasting

Although there are intermittent fasting studies on men, there aren’t many that have involved women. Hormonal cycles and different nutritional requirements may introduce some differences. According to Medical News Today,10 women need more iron, and fasting may not adequately fulfill their need. However, fasting may help to:

  • Lower blood sugar levels and decrease weight11
  • Optimize eating and sleeping cycles for obese people and increase their life expectancy12
  • Benefit both your heart and verbal memory performance13

In 2010 researchers conducted a five-year study14 involving adolescent girls and found that fasting for 24 hours for weight control “would be a more potent predictor of binge eating and bulimic pathology onset than dietary restraint.” They concluded that such measures would increase the risk of bulimic episodes and other types of binge eating. However, skipping food for 24 hours is not what OMAD suggests.

Especially since OMAD has been identified as an extreme diet plan, possible risks have also been assessed, and some of those risks include extreme hunger and shakiness, weakness, fatigue, irritability and “foggy” thought processes. Certain people are advised not to try the OMAD method, including pregnant and nursing mothers, those with eating disorders such as anorexia, and people with diabetes.15

Comparing OMAD, intermittent fasting and the ‘warrior diet’

Whether discussing OMAD, intermittent fasting or the warrior diet,16 there are pros and cons to consider, according to Land, as discussed in the video:

  • Intermittent fasting is described by Land as being easy for beginners. It allows 16 hours for digestion and increases mental clarity. However, the timeframes may not be long enough to trigger significant autophagy, a natural process required to renew damaged cells, and the actual fasting state only begins when your food has digested. Additionally, hunger, sugar cravings and “cheating” may derail the process during your eight-hour eating time.
  • The warrior diet, which entails fasting most of the day, causes you to lose fat more easily and go deeper into ketosis. It’s easier because you have fewer cravings; you can eat a lot without worrying about calories; autophagy increases and digestion may improve. But the cons include more difficulty with strength and resistance training; a possible struggle with too much coffee and other stimulants; binge eating and possibly muscle loss as a result; and jeopardized sleep.
  • OMAD makes fat easy to lose and autophagy and mental clarity more readily acquired; Land says hunger practically disappears; your digestive system has more time to work; your body becomes more efficient at utilizing nutrients and you can eat more carbs while maintaining ketosis.

As for the cons of OMAD, Land says muscle is harder to build and protein synthesis is harder to gain; consuming the calories you need in such a small window is difficult and may lead to bloating and discomfort; sleep quality may suffer eating close to bedtime and the diet may cause metabolic stress if maintained for too long.

“OMAD and the warrior diet are definitely not optimal for muscle growth or resistance training, but they’re still very effective for maintenance and fat loss,” Land says. “At the minimum, I would still recommend (that you) stick to a daily eating schedule and try to consume all your calories within at least eight to 10 hours.” It benefits your circadian rhythm, he adds, as well as reducing insulin resistance and increasing metabolic effects and glucose tolerance.

Land: More observations of OMAD

After being on a combined OMAD and warrior diet for “at least three or four years,” Land says he’s never felt better. His reply to OMAD naysayers is that it’s not the “one hour” factor that makes people get sick, but their current lifestyle factors, including overeating, poor sleep and lack of exercise. However, he says, OMAD does have caveats:

“If you suffer from chronic stress, then eating once a day isn’t going to save you. If your nutrition in general isn’t nutrient intense — you’re not getting enough essential nutrients within that small time frame of OMAD, then, yes, it … might not inherently damage your health, but it won’t be as optimal as it could be.”

He maintains that if you’ve researched longevity and autophagy — a natural process triggered by intermittent fasting that’s required to renew damaged cells — intermittent fasting is the best thing you can do to prevent disease and slow the aging process. In fact, unless you’re a high-performance athlete, eating once a day is something to opt for, as “There’ isn’t any real physiological reason to be eating any more frequently.”

“It’s actually the opposite of what happens with a lot of frequent meals with a bunch of carbs and not controlling your other macronutrients,” Land says, adding that unhealthy eating keeps your body in a continuous fat state and doesn’t allow it to repair itself.

If an OMAD diet doesn’t currently appeal to you, he suggests starting with a standard 16/8 intermittent fasting diet, restricting your food intake to an eight-hour window. Either way, you should optimize your eating plans to maximize your results.

One rule is to limit your fasts, though; extended fasts aren’t recommended. If you’re doing a 16/8 but also including a 48-hour fast every week, or a three-day fast every week or so, he says, it balances itself out.

Top tips for sticking to an OMAD diet

OMAD is a “pretty effective strategy for doing intermittent fasting and losing weight,” Land says. Centering your calorie intake into one to two hours of your day may be a simple concept, “but some people can still mess it up.” For them, the above video offers Land’s top 10 tips to help with the OMAD diet:

  1. Go for long walks — Because your glycogen is already low and you’re producing ketones, walking in a fasting state is a great way to burn more fat.
  2. Drink salted water in the morning — A glass of water with a pinch of sea salt lowers your cortisol and helps with stress, digestion and gut health.
  3. Postpone caffeine — Drinking caffeine right after waking up stimulates cortisol, your body’s main stress hormone, sometimes referred to as nature’s built-in alarm clock. Wait two to three hours for naturally lower cortisol levels.
  4. Stay productive — With fasting you’re not wasting time eating (or thinking about it). Fasting increases focus and alertness while eliminating distractions.
  5. Avoid artificial sweeteners — Avoiding artificial sweeteners altogether is important if you have trouble controlling cravings but avoiding sugar itself is paramount. Stevia is a natural sweetener that doesn’t raise your glucose index.
  6. Train at the end of your fast — It preserves more muscle mass and benefits your body’s composition. Plus, your body needs the fuel before the workout.
  7. Plan your OMAD meal — If you reach for whatever you find in the refrigerator, you’ll likely compromise with “randomness, cluelessness and potentially bingeing.”
  8. Eat your OMAD early — While there’s no difference metabolically what time you eat, eating too late is notorious for compromising your sleep.
  9. Focus on nutrient-dense foods — During the few hours of eating, whether it’s a six- or one-hour window, healthy food intake is crucial.
  10. Change up your routine — While OMAD is quite effective, changing your eating times keeps your body more metabolically flexible.

Ways to approach the OMAD diet

How can you take in all the calories you need in a day in just one hour? I’m challenged by the concept, but especially if you’re working out, you would need to eat around 3,000 calories in one meal. Personally, I wouldn’t do it regularly or for an extended length of time; I like eating over a longer period.

Intermittent fasting is a better approach, because you have four to six hours to eat. That may not be a lot, but it’s better than restricting it to just one hour. However, if you’re intrigued by the concept of eating one meal a day in a short window of time, shrinking the window gradually might be a good way to get started.

If necessary, you could first try restricting your eating time within a six- or eight-hour window, then lower it to four or six hours, then to three before cutting it down to just one meal a day. However, some eat their one meal as dinner, which for some people is 6 p.m., 7 p.m. or even 8 p.m. But I wouldn’t choose to eat my one meal at that time of day; as I’ve said many times, it’s not good to eat right before bed.

Choosing your OMAD within an hour or two following an early-morning workout would be best. Tackling the one-meal-a-day regimen to build your muscles and maximize your catabolism involves the breakdown of nutrient molecules into the usable forms or building blocks, according to the scientific journal Nature Education. In essence:

“In this process, energy is either stored in energy molecules for later use, or released as heat. Anabolic pathways then build new molecules out of the products of catabolism, and these pathways typically use energy. The new molecules built via anabolic pathways (macromolecules) are useful for building cell structures and maintaining the cell.”17

When implementing a fasting regimen, your body begins to downregulate protein catabolism and upregulates growth hormones in response. In fact, Jason Fung, a Canadian kidney specialist who co-wrote “The Complete Guide to Fasting,” notes that your body never upregulates its protein catabolism or burns muscle. Instead, fasting kick-starts the burning of glycogen, aka sugar, in your liver, after which you begin burning fat as your fast continues.18