OMAD Diet (One Meal a Day): How It Works, Results and Risks

OMAD, short for “one meal a day”, means eating all your food in a single meal, usually within about an hour, and fasting for the other 23 hours. During the fast you drink water, black coffee and plain tea. It is the strictest form of daily intermittent fasting.

OMAD can work for weight loss, mainly because most people eat less when they only sit down to eat once. The two controlled trials of one meal a day were small and short, it makes many people very hungry, and in one trial it raised blood pressure and LDL cholesterol. Here is how it works, what the research shows, what to eat, and who should avoid it.

How OMAD Works

Most people eat their meal in the late afternoon or evening so it fits family dinners, but any fixed time works. Some people allow a 2-hour window (22:2) to make the meal easier to fit in. Not sure if a drink counts? Check our what breaks a fast tool.

To see how many calories, and how much protein, carbs and fat, to fit into your one meal, use our OMAD calculator.

What the Research Shows

Only two controlled trials have tested one meal a day directly. In both, people ate the same number of calories as on three meals, so any difference came from the timing:

• Stote 2007: healthy, normal-weight adults ate either one meal or three meals a day for 8 weeks each. On one meal a day they lost a little fat mass, but they were significantly hungrier, and their blood pressure and total, LDL and HDL cholesterol went up. (1)
• Meessen 2022: 11 lean adults ate either three meals or one evening meal (5 to 7 PM) for 11 days each. On one meal a day they lost more weight (1.4 kg vs 0.5 kg) and more fat mass (0.7 kg vs 0.1 kg), burned more fat during exercise, and kept their strength and aerobic fitness. (2)

Both studies were small, short and in healthy people, so they can’t tell you how OMAD works over months, or in people with obesity or diabetes. They suggest a small extra fat-loss effect at the same calories, with a cost in hunger and, in one study, blood pressure and cholesterol.

Does OMAD Work for Weight Loss?

Yes, for most people, because it is hard to eat a full day’s calories in one sitting. You still lose weight only if you eat less than you burn. A large meal of 3,000 calories every evening won’t cause weight loss for most people, however long the fast.

What to Expect After 30 Days

As an example: if you burn about 2,200 calories a day and your one meal is about 1,500, that is a 700-calorie daily deficit, or roughly 1.4 pounds of fat a week, about 5 to 6 pounds in 30 days. The scale may show more in the first week, mostly water. Find your own daily burn with our TDEE calculator.

What to Eat on OMAD

There are no banned foods, but one meal has to cover a whole day’s nutrition, so build it with care:

• A large serving of protein: meat, fish, eggs, Greek yogurt, tofu or beans. A whole day’s protein in one sitting is hard to reach, which is one reason OMAD can cost muscle. Our protein calculator gives you a target.
• Plenty of vegetables and some fruit for fiber, vitamins and minerals.
• Whole-food carbs: potatoes, rice, oats, whole grains or legumes.
• Healthy fats: olive oil, avocado, nuts and seeds.

A good OMAD meal often looks like two plates: for example, salmon with potatoes and roasted vegetables, followed by Greek yogurt with berries and nuts. Low-carb eaters can follow our keto OMAD guide.

OMAD vs Other Fasting Schedules

If OMAD feels too hard, a 4-hour or 8-hour window gives most of the practical benefit (fewer meals, less snacking) with less hunger. Compare all the options in our fasting protocols, or read how OMAD compares with alternate day fasting.

Downsides of OMAD

• Hunger. People were significantly hungrier on one meal a day in the 8-week trial. (1)
• Blood pressure and cholesterol. The same trial found blood pressure and LDL cholesterol rose. If you stay on OMAD, get them checked.
• Hard to meet your nutrient and protein needs in one sitting, especially if you are active.
• Overeating. Some people binge at the one meal, which cancels out the deficit and can feed an unhealthy relationship with food.
• Training. Hard sessions late in a long fast can feel weak or light-headed. Many lifters and athletes find it hard to eat enough on OMAD to recover and build muscle.
• Social life. Breakfasts, lunches and shared meals don’t fit.

Who Should Not Do OMAD

Talk to your doctor first, or avoid OMAD, if you:

• Have diabetes, or take insulin or other medication that lowers blood sugar
• Take blood pressure medication or have high cholesterol or heart disease
• Are pregnant or breastfeeding
• Are under 18, or still growing
• Are underweight, or have, or have had, an eating disorder

How to Start OMAD

1. Work up to it. Start with 16:8, then move to 20:4, before going to one meal.
2. Pick a fixed meal time you can keep most days.
3. Plan the meal. Protein first, then vegetables, then carbs and fats.
4. Drink through the day: water, black coffee and tea.
5. Give it 2 weeks, and stop if you feel unwell, binge, or your training falls apart.

FAQs

Is OMAD healthy?

It can be safe for healthy adults in the short term, but it isn’t healthier than other ways of eating less. In one trial it raised blood pressure and LDL cholesterol even without weight change. (1)

Will I lose belly fat on OMAD?

You will lose fat from your whole body, including your belly, if you eat less than you burn. No diet targets belly fat specifically.

What can I drink during the fast?

Water, sparkling water, black coffee and plain tea. Milk, juice, smoothies and sugary drinks break the fast.

Can you build muscle on OMAD?

It is possible but harder, because you need enough protein and calories in one meal. If muscle gain is your main goal, a wider eating window makes it easier.

How long can you do OMAD?

There is no long-term research. Some people do it for weeks or months; many find it too hard to keep up. If you stay on it, check your blood pressure and cholesterol.

The Bottom Line

OMAD means one meal a day and a fast of about 23 hours. It helps many people lose weight because it is hard to overeat in one meal, and two small trials found a little extra fat loss at the same calories. It also makes many people hungrier and, in one trial, raised blood pressure and LDL cholesterol. Build your meal around protein and vegetables, ease in from 16:8 or 20:4, and talk to your doctor first if you have a health condition.

References

Fitness Volt is committed to providing our readers with science-based information. We use only credible and peer-reviewed sources to support the information we share in our articles.

1. Stote KS, Baer DJ, Spears K, et al. A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults. Am J Clin Nutr. 2007;85(4):981-988.
2. Meessen ECE, Andresen H, van Barneveld T, et al. Differential Effects of One Meal per Day in the Evening on Metabolic Health and Physical Performance in Lean Individuals. Front Physiol. 2022;12:771944.