OMAD and the Warrior diet: one meal a day is simple. Simple isn't the same as smart.
Eat once, fast for 20 to 23 hours, repeat. It's the bodybuilder's favourite flex and a real eating pattern with real studies. They're just not as flattering as the YouTube videos.
The short version
- What it is
- OMAD: one meal a day (23:1). Warrior diet: a 4-hour feast after a day of fasting (20:4).
- Good for
- Simplicity. Eating less without counting. Busy people who forget lunch anyway.
- Bad at
- Hunger, getting enough protein in one go, and blood pressure and cholesterol in one small trial.
- Evidence
- Weak. A handful of small, short studies.
- Our take
- The extreme end of the eating window. Fine on some days, not a way to live for most people.
What OMAD and the Warrior diet actually are
OMAD is exactly what it says: one meal a day. You eat once, usually in the evening, and fast the other 23 hours. It's the far end of time-restricted eating.
The Warrior diet came first. It was set out by Ori Hofmekler in a 2001 book: undereat during the day (some raw fruit and vegetables, small amounts of dairy or eggs), then eat one big meal in a 4-hour evening window.1 The idea was that ancient warriors fought all day and feasted at night. There's no evidence ancient warriors ate like that, and you're probably not storming a castle after work.
Both boil down to the same thing: a 20- to 23-hour daily fast with one large meal.
How it works in your body
Same mechanism as all fasting, turned up to eleven. Long hours without food mean low insulin and more fat burned for fuel. And because it's really hard to eat a full day's food in one sitting, most people simply eat less.
That's what happened in a Chicago trial: adults with obesity eating in a 4-hour window (3 to 7 pm, basically the Warrior diet) ate about 550 calories a day less and lost about 3% of their weight in eight weeks. A 6-hour window did just as well.2 Going from six hours to four added nothing but suffering.
What you eat, what you don't
Eat (in the one meal)
- A big portion of protein: fish, meat, eggs, tofu, tempeh
- Two or three kinds of vegetables, a lot of them
- Lentils, beans, or a fist of whole grains or potatoes
- Olive oil, avocado, nuts
- Fruit or Greek yoghurt as dessert, straight after
- During the fast: water, black coffee, green tea
Forget it
- Turning the one meal into a pizza-and-ice-cream binge
- Fast food as "the meal". One meal has to carry a whole day.
- Sugar, soft drinks, juice
- "Just a little" snacking during the day
- Sweeteners and "zero" drinks during the fast
- Hard training late in a 23-hour fast with nothing in the tank
Alcohol on OMAD and the Warrior diet
OK, now and then
- One glass of dry wine with the meal, not before
- Spirits with soda water and lime, during the meal
- One light beer with food
Out
- An aperitif after 23 hours of fasting. It hits fast and hard.
- Drinks during the fasting hours
- Several rounds "because it's the only meal"
- Cocktails, liqueurs, beer by the pint
50 Club: one glass with the meal, after you've eaten something.
After nearly a full day without food, alcohol meets an empty stomach. Never drink before you eat. And while your liver deals with alcohol, fat burning stalls: two drinks cut it by about 73% in one small study.7 All the details are in our alcohol guide.
What OMAD is good for, with proof
Eating less without thinking about it
A short window caps how much most people can eat. In the 4-hour group of the Chicago trial, calories dropped by about 550 a day without anyone counting.2 For people who keep forgetting what they've eaten, one meal is easy to keep track of.
A little fat loss, even at the same calories
In a small US government study, healthy normal-weight adults ate either three meals or one evening meal a day, with the same total calories, for eight weeks each. On one meal a day, fat mass dropped somewhat, by about 2 kg compared with three meals.3 Only 15 people finished, so treat it as a hint, not a rule.
The uncomfortable truth
"OMAD is the healthiest way to eat." The same small study that found less fat also found the downsides. On one meal a day, people were significantly hungrier, their blood pressure went up, and total and LDL ("bad") cholesterol went up too.3 A follow-up from the same group showed worse blood sugar control in the morning after the single evening meal.4
Only 15 people, eight weeks each. It doesn't prove OMAD harms you. But the only controlled data on true one-meal-a-day eating points both ways, and anyone who sells it as the perfect diet hasn't read it.
The risks
- Too little protein. Your body uses protein best spread over meals, roughly 25 to 30 g each.5 Cramming a day's worth into one sitting is hard, and muscle pays. See our high-protein article.
- Blood pressure and cholesterol. Both rose on one meal a day in the controlled study.3 If yours are already high, check them before and after.
- Diabetes medication. A 23-hour fast on insulin or similar drugs can cause dangerous lows. Fasting days roughly doubled hypos in a type 2 diabetes trial.6 Not without your doctor.
- Binge-and-starve. OMAD can tip into a cycle of starving all day and losing control at night. Intermittent fasting has been linked with eating-disorder behaviours, including binge eating.8
- Missing nutrients. One plate has to deliver all your fibre, vitamins and minerals. Most one-meal days don't.
- Feeling rubbish. Headaches, low energy, poor focus and an irritable afternoon are common, especially early on.
Allergies: watch the staples
OMAD has no fixed food list, but a single meal built for maximum protein leans on the usual suspects.
| Staple | Allergen (EU list of 14)9 | Swap |
|---|---|---|
| Eggs | Eggs | Fish, chicken, tofu |
| Cheese, yoghurt dessert | Milk | Soy yoghurt, fruit, seeds |
| Salmon, tuna | Fish | Chicken, lentils, chia and flax for omega-3 |
| Prawns, mussels | Crustaceans, molluscs | Chicken, fish |
| Nuts as dessert | Tree nuts, peanuts | Pumpkin and sunflower seeds |
| Tofu, tempeh | Soy | Lentils, chickpeas, eggs |
Don't do OMAD if you…
- are pregnant or breastfeeding
- are under 18
- have ever had an eating disorder or tend to binge
- take insulin, sulfonylureas, SGLT2 or GLP-1 drugs
- are underweight, frail or over 70 and losing muscle
- have high blood pressure or high LDL that isn't monitored
- have kidney disease
Healthen me asks about all of these and gives you a different plan if any apply.
How we use OMAD in your plan
OMAD is a building block at the very top of the eating-window scale. We never put you on it by default. Our rule is to fast as long as you comfortably can, and for most people that's two meals in a shorter window, not one.
If you tell us you already eat once a day and feel good, the plan keeps it, but makes that one meal count: protein first, a mountain of vegetables, good fat, and dessert straight after if you want it. If you're under 18, pregnant, on diabetes drugs or have any eating-disorder history, OMAD is off the table. Longer fasts sit in extended fasting, which is doctor territory.
This article is general information, not medical advice. If you have a medical condition or take medication, talk to your doctor before changing how you eat.
Sources
- Hofmekler O, Holtzberg D. The Warrior Diet. St. Paul, MN: Dragon Door Publications, 2001 (reissued by North Atlantic Books, 2007).
- Cienfuegos S et al. Effects of 4- and 6-h time-restricted feeding on weight and cardiometabolic health: a randomized controlled trial in adults with obesity. Cell Metabolism 2020;32(3):366–378. doi.org/10.1016/j.cmet.2020.06.018
- Stote KS et al. A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults. American Journal of Clinical Nutrition 2007;85(4):981–988. doi.org/10.1093/ajcn/85.4.981
- Carlson O et al. Impact of reduced meal frequency without caloric restriction on glucose regulation in healthy, normal-weight middle-aged men and women. Metabolism 2007;56(12):1729–1734. doi.org/10.1016/j.metabol.2007.07.018
- Leidy HJ et al. The role of protein in weight loss and maintenance. American Journal of Clinical Nutrition 2015;101(6):1320S–1329S. doi.org/10.3945/ajcn.114.084038
- Corley BT et al. Intermittent fasting in type 2 diabetes mellitus and the risk of hypoglycaemia: a randomized controlled trial. Diabetic Medicine 2018;35(5):588–594. doi.org/10.1111/dme.13595
- Siler SQ, Neese RA, Hellerstein MK. De novo lipogenesis, lipid kinetics, and whole-body lipid balances in humans after acute alcohol consumption. American Journal of Clinical Nutrition 1999;70(5):928–936. pubmed.ncbi.nlm.nih.gov/10539756
- Ganson KT et al. Intermittent fasting: describing engagement and associations with eating disorder behaviors and psychopathology among Canadian adolescents and young adults. Eating Behaviors 2022;47:101681. doi.org/10.1016/j.eatbeh.2022.101681
- Regulation (EU) No 1169/2011 on food information to consumers, Annex II (the 14 allergens). eur-lex.europa.eu/eli/reg/2011/1169/oj