OMAD, one meal a day: who it suits and how to eat it well

1. Understand what OMAD, one meal a day, asks of you

In practice OMAD means an eating window of 60 to 90 minutes, often written as 23:1, and a fast of 22 hours or more every single day. A typical weekday looks like this: black coffee or plain tea in the morning, water through the afternoon, dinner from 6:00 to 7:30 pm, then nothing until the next evening.

That makes it a step beyond 20:4, where a four-hour window still leaves room for two smaller meals. It is also very different from 5:2, where you eat little on two days a week and normally on the other five.

Most people who do OMAD comfortably got there in stages: 16:8 for a few weeks, then 18:6, then 20:4. If 20:4 already leaves you irritable by 4 pm, one meal will feel harder still. Doing OMAD two or three days a week, with two meals on the other days, is a sensible middle ground.

2. Decide whether OMAD suits you

OMAD fits a narrow set of people. Use this table as a first filter.

Your situation	OMAD?	Why
Healthy adult already comfortable with 18:6 or 20:4	Can try it	The step is small and you know how you handle long fasts
You lift weights or want to gain muscle	Two meals usually work better	Protein is easier to spread over two meals than to squeeze into one
Diabetes treated with insulin or tablets that lower blood sugar	Only with your doctor	A 23-hour gap raises the risk of low blood sugar, and doses often need changing
High blood pressure or high LDL cholesterol	Check first, then monitor	Both rose on one meal a day in a controlled trial
Pregnant, breastfeeding, under 18 or a history of eating disorders	No	Needs are higher, and one large daily meal can feed a restrict and binge cycle
Over 65 with a small appetite or recent unplanned weight loss	Usually no	Eating enough protein in one sitting is very hard

Your calendar matters too. Team lunches and a family dinner at 5:30 pm turn one meal a day into a constant negotiation. OMAD works best when your evenings are predictable and you genuinely do not miss lunch.

3. Know what the studies on one meal a day found

The best-known trial, from US government researchers, was published in 2007. Healthy, normal-weight, middle-aged adults ate all the calories they needed to keep their weight stable, either as three meals or as one meal a day, for eight weeks each. Weight stayed within 2 kg throughout. On one meal a day the volunteers lost some fat mass, but they also reported significantly more hunger, and their blood pressure rose along with total, LDL and HDL cholesterol.

A second analysis of the same volunteers, who ate their single meal between 4 and 8 pm, found higher fasting blood sugar in the morning and a slower insulin response to a glucose drink. Those changes went away once they returned to three meals.

A more recent crossover study from the Netherlands and Norway gave 11 lean adults aged around 30 one meal a day between 5 and 7 pm for 11 days, again with enough calories to maintain weight. They lost about 1.4 kg on average compared with 0.5 kg on three meals, about 0.7 kg of it fat mass. Strength and aerobic capacity held up, and blood sugar was lower in the second half of the day.

Every one of these trials was small and lasted weeks. Most volunteers were lean and healthy, so the results may not apply to someone with obesity or diabetes, and no study has tracked OMAD over years.

4. Build the one meal around protein

Protein is where a single meal gets tricky. The standard reference intake is 0.8 g per kilogram of body weight a day, which comes to about 56 g for someone weighing 70 kg, and people who train or are over 50 usually aim higher. On OMAD all of it has to fit on one plate.

Timing may matter as well. In a small one-week study, eight adults who ate about 30 g of protein at each of three meals had 25% higher muscle protein synthesis over 24 hours than when most of their protein, around 63 g, came at dinner. One meal a day is the most lopsided pattern there is, so if keeping or building muscle is your priority, a 20:4 window with two protein-rich meals is the safer choice. Our article on intermittent fasting and muscle loss goes further.

Make the protein a generous portion. A 150 g cooked chicken breast gives about 45 g, and a 200 g pot of Greek yogurt after the main course adds another 20 g. If you train, do it in the hours before your meal so the meal doubles as recovery. To check whether you hit the target, scan the plate with FastTrack, which estimates calories and macros from a photo.

5. Fit 25 to 30 grams of fiber into a single sitting

Fiber is the other target that one meal makes hard. A large review of cohort studies and trials in The Lancet found the biggest drops in the risk of conditions such as heart disease and type 2 diabetes at intakes of 25 to 29 g a day.

Getting 25 g into one sitting takes a lot of plants. Here is one plate that covers both targets:

Food	Portion	Protein, about	Fiber, about
Salmon fillet, cooked	180 g	40 g	0 g
Lentils, cooked	200 g	18 g	16 g
Roasted broccoli	200 g	5 g	7 g
Greek yogurt with 1 tbsp chia seeds	200 g	22 g	4 g
Raspberries	125 g	1.5 g	8 g
Total	One large meal	About 85 g	About 35 g

That plate is only about 1,000 kcal, so most adults still need rice, potatoes, wholegrain bread or olive oil on top. Eating too little is a real risk on OMAD.

Raise fiber over two or three weeks if you are used to 15 g a day, and drink water with the meal, because 35 g at once can cause bloating. Canned beans, frozen vegetables and microwave lentil pouches help on a weeknight. If you still fall short, a teaspoon of plain psyllium husk in water adds a few grams; our page on whether psyllium husk breaks a fast explains which versions you can also take during the fasting hours.

6. Time the meal and eat it slowly

The studies above placed the meal in the late afternoon or early evening, a slot that suits most working days. Try to finish two to three hours before bed, since a very large meal followed by lying down often brings heartburn and restless nights.

Give yourself 45 to 60 minutes. Start with the vegetables and the protein, move to the starches, and leave fruit or dessert for the end. A meal this size eaten in 15 minutes tends to leave you uncomfortably full and still wanting more, because the signals of fullness lag behind your fork.

During the fasting hours, drink water, black coffee or plain tea before you feel thirsty. FastTrack can start and stop your fast automatically around your mealtime, so the timer keeps running even on days you forget to tap it.

7. Watch your numbers and know when to stop

Have your blood pressure measured and a lipid panel done before you start and again after two or three months, since both went up in the 2007 trial. If you have prediabetes, ask your doctor about a glucose test as well, given the higher morning blood sugar in the same volunteers.

Hunger is the most common complaint, and it was significantly higher on one meal a day in that trial. Some hunger in the first two weeks is expected and tends to come in waves; our guide to hunger while fasting has practical ways to get through them. If the hunger keeps building week after week, or you find yourself eating until you feel sick, go back to two meals.

Stop and talk to a doctor if you notice any of the following:

• Dizziness or fainting, especially when you stand up.
• Shakiness, sweating or confusion if you take diabetes medication.
• Palpitations, or headaches that do not settle after you eat and drink.
• Binge eating or guilt around food, particularly with a past eating disorder.
• Hair loss, missed periods or weight loss you did not plan.

OMAD is off the table if you are pregnant or breastfeeding, under 18, or have a history of eating disorders.

The honest verdict

OMAD can work for healthy adults who like a simple day and already handle long fasts well. The evidence is short-term, and the 2007 trial found more hunger and higher blood pressure alongside a little fat loss. If you try it, build the meal around protein and fiber, check your numbers after a few months, and remember that a 20:4 window with two meals is a perfectly good place to land.