You’ve probably seen the guy at the office or the fitness influencer on your feed who swears by it. They skip breakfast. They ignore lunch. Then, around 7:00 PM, they sit down and demolish a massive plate of steak, sweet potatoes, and greens. It's called OMAD—One Meal a Day. But the real question is simple: is it healthy to eat once a day, or are we just starving ourselves in the name of productivity and a flatter stomach?
Honestly, the answer isn't a clean "yes" or "no." It’s complicated.
Humans weren't always grazers. Our ancestors didn't have refrigerators or 24-hour drive-thrus. They hunted, they gathered, and they ate when they found food. Sometimes that was once a day; sometimes it was once every three days. Evolutionarily speaking, our bodies are built to handle periods of nothingness. But just because we can survive on one meal doesn't mean we’re thriving on it in a modern context where stress levels are through the roof and our sleep is garbage.
The Science of Doing Less
When you stop eating for 23 hours, your body starts doing some pretty weird, and potentially cool, things. After about 12 to 16 hours, you hit a state called autophagy. This is basically cellular spring cleaning. Your body starts identifying old, damaged protein structures and "recycling" them. Nobel Prize winner Yoshinori Ohsumi won his award for researching this exact process. It's a massive deal for longevity.
But there is a catch.
Most people trying to figure out if it is healthy to eat once a day are looking for weight loss. And yeah, it works for that. It’s hard to overeat 2,500 calories in a single sitting unless you’re trying really hard. Your insulin levels drop. Your growth hormone spikes. You start burning fat because there’s no glucose coming in from a mid-afternoon granola bar.
But here is where things get dicey. Dr. Peter Attia, a well-known longevity expert, often notes that while fasting can be great for metabolic health, it can also lead to significant muscle loss if you aren't careful. If you lose ten pounds and five of those pounds are muscle, you haven't really "won." You’ve just lowered your metabolic rate, making it easier to gain the fat back later.
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Why OMAD Kills Your Energy (Sometimes)
Have you ever felt "hangry"? Now imagine that feeling stretched over eight hours of a workday.
For some, the mental clarity is insane. They feel like they have a superpower. This happens because the body produces orexin-A, a neuropeptide that keeps you alert when you’re hungry—it's a survival mechanism to help you find food. But for others? It’s a nightmare. Cortisol (the stress hormone) can skyrocket. If you’re already a high-stress person with a demanding job and three kids, adding a 23-hour fast might be the straw that breaks the camel's back.
Your thyroid doesn't love long-term calorie deprivation either. T3, your active thyroid hormone, can drop when the body thinks it's in a famine. You might feel cold all the time. Your hair might thin. You might just feel... "meh."
Is it healthy to eat once a day for women?
This is a huge point of contention. Most fasting studies were done on men or post-menopausal women. For women of reproductive age, the "is it healthy to eat once a day" question gets a lot more "no-ish."
Women’s bodies are incredibly sensitive to nutrient scarcity. If the brain senses there isn't enough food coming in consistently, it might downregulate reproductive hormones. This is why some women on OMAD lose their periods or experience wild mood swings. Dr. Stacy Sims, a specialist in female physiology, famously argues that "women are not small men" and that extreme fasting can often do more harm than good for female metabolic health and bone density.
If you’re a woman, jumping straight into one meal a day is like trying to run a marathon without training. It’s a shock to the system.
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The "One Meal" Logistics Problem
Let's talk about the actual food. If you’re only eating once, that meal has to be a masterpiece of nutrition.
You need enough protein to maintain your muscles—usually at least 30 to 50 grams in that one sitting. You need fiber so you don't end up constipated. You need all your vitamins and minerals. Most people can't actually cram all that into one sitting. They end up eating a giant bowl of pasta or a burger and calling it a day. That leads to nutrient deficiencies.
- You might lack Magnesium, leading to leg cramps.
- Zinc levels might drop, hurting your immune system.
- Vitamin D is hard to get from food anyway, let alone one meal.
So, is it healthy? If that one meal is a mountain of diverse veggies, high-quality protein, and healthy fats, maybe. If it’s a pepperoni pizza? Absolutely not.
Social Life and the "Weirdo" Factor
Health isn't just about blood markers and body fat percentages. It’s about being a human. Eating is a social act.
When you commit to eating once a day, you become the person who sits at the lunch meeting with a glass of black coffee while everyone else is enjoying a sandwich. You’re the one who can’t go out for brunch on Sunday. For some, this discipline is empowering. For others, it’s isolating. If your diet makes you a hermit, is it actually "healthy"? Mental health matters. Social connection matters.
What the Experts Say
The National Institutes of Health (NIH) conducted a study on rhesus monkeys—our close relatives—and found that those on calorie-restricted diets lived longer, but they weren't necessarily "happier" or more active. In humans, a 2022 study published in the New England Journal of Medicine found that time-restricted eating (like OMAD) didn't actually provide significantly more weight loss than standard calorie counting over a 12-month period.
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Basically, the "magic" of OMAD might just be that it's an easy way to eat less. There’s no metabolic voodoo happening that makes calories disappear.
The Verdict on Your Stomach
So, is it healthy to eat once a day?
It can be a powerful tool for certain people—specifically those with Type 2 diabetes or insulin resistance, under medical supervision. It can help reset your relationship with hunger. It can save you a ton of time on meal prep.
But it's not a silver bullet.
For many, it leads to a "binge and restrict" cycle that looks a lot like an eating disorder. You starve all day, then lose control at night because your brain is screaming for glucose. That’s not health; that’s a roller coaster.
How to do it without breaking yourself
If you're still dead-set on trying it, don't just stop eating tomorrow. That’s a recipe for a massive headache and a bad mood.
- Start with 16:8. Eat within an 8-hour window. See how you feel.
- Hydrate like a maniac. Most "hunger" during a fast is actually just dehydration or a lack of electrolytes. Drink salt water or a zero-sugar electrolyte mix.
- Prioritize Protein. When you finally eat, eat the chicken or the steak first. If you fill up on bread, you’re failing the nutritional requirements of the day.
- Listen to your body. If you feel dizzy, shaky, or genuinely weak, eat. The "fasting police" aren't coming to arrest you.
- Check your bloodwork. If you're doing this long-term, get your lipids and hormone levels checked. Don't guess.
Ultimately, the healthiest way to eat is the way that you can sustain for ten years, not ten days. If eating once a day makes you feel like a rockstar, go for it. If it makes you feel like a zombie, grab a snack.
Actionable Next Steps
- Audit your current hunger: For the next three days, don't change what you eat, but track when you are actually hungry versus just bored. This will tell you if OMAD is even a natural fit for your rhythm.
- Supplement your fast: Buy a high-quality, unflavored electrolyte powder. Taking this during your fasting hours can prevent the "fasting flu" (headaches and fatigue).
- Plan your "Break-Fast": Your first meal shouldn't be a carb bomb. Have a small snack like a few walnuts or a hard-boiled egg 30 minutes before your "big" meal to wake up your digestive enzymes.
- Schedule a blood panel: Before starting any extreme dietary shift, get a baseline for your A1C, fasting insulin, and CRP (inflammation) levels so you can actually measure if the change is "healthy" for your specific biology.