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OMAD (one meal a day)

DebatedUpdated October 31, 2026 · 17 studies · Written by the AumniVIDA team

What is omad (one meal a day)?

OMAD, or one meal a day, is the most compressed form of intermittent fasting: you eat all of the day's food in a single meal, usually within about one hour, and fast for roughly 23 hours. It cuts calories for most people, but small controlled trials found worse morning blood sugar and higher LDL cholesterol than three meals.

A single large plate with salmon, lentils, roasted vegetables and greens beside a bowl of berries on a linen-covered table.
On OMAD, a single meal has to cover the day's protein, fiber and micronutrients.

OMAD has almost no long-term trials. One 8-week controlled crossover trial, reported in two papers, and one 11-day trial exist, alongside a trial of a 4-hour window. They show fat loss but also higher blood pressure, higher LDL cholesterol and worse morning glucose tolerance with an evening meal. Large observational studies link eating once a day to higher mortality, which cannot prove cause.

The rules

The rules ofOMAD (one meal a day)

Debated in mainstream science5 rules
  1. 1Eat all food and caloric drinks in one meal, finished within about 1 hour.
  2. 2Fast for the other 23 hours, taking only water, black coffee, plain tea or other zero-calorie drinks.
  3. 3Eat the meal at about the same time each day.
  4. 4Make the one meal cover the full day's needs for energy, protein, fiber and micronutrients.
  5. 5Repeat daily, or on set days of the week if you follow a part-time version.

Share these rules as an image or a link.

Common variants
Strict OMAD (23:1)One meal inside a 1-hour window every day.
22:2One meal stretched over 2 hours, as in a trial that served it from 5 to 7 p.m.
20:4A 4-hour window, often one large meal plus a snack, as in a trial that allowed eating only from 3 to 7 p.m.
Evening OMADThe single meal at dinner time, a common choice because it fits family and social meals.
Early OMADThe single meal in the late morning or early afternoon, chosen to suit the body clock.
Part-time OMADOne meal a day on two or three days a week, with normal eating on the others.

What it aims to do

  • Create a large calorie deficit with one simple rule.
  • Lose body fat without tracking food.
  • Spend most of the day past the metabolic switch, running on fat and ketones.
  • Save time on cooking and eating.
  • Boost cell repair (autophagy), a claim with little human evidence.

What it claims, and what the evidence shows

Grades reflect evidence in people. Animal and cell results alone never earn more than limited.

  • Body fat and weight

    Limited evidence

    Causes fat loss

    Short controlled trials show fat loss even without fewer calories, and a 4-hour window cut about 550 kcal a day, but no trial has run longer than 8 weeks per arm. [1][2][3][4]

  • Blood sugar and insulin

    Mixed evidence

    Improves blood sugar and insulin

    An evening single meal raised morning fasting glucose and worsened glucose tolerance over 8 weeks, while an 11-day trial found lower glucose later in the day. [5][2][6][3]

  • Heart and blood vessels

    Evidence against

    Improves heart health

    In a controlled trial, one meal a day raised blood pressure and LDL cholesterol, and in a US cohort eating once a day was linked to 83% higher cardiovascular mortality. [1][7][8]

  • Muscle and strength

    Mixed evidence

    Keeps muscle and strength

    Strength held over 11 days, and a large protein dose builds muscle for over 12 hours, but spreading protein across meals built more muscle in another study. [2][9][10][11]

  • Athletic performance

    Limited evidence

    Keeps exercise performance

    In lean adults, 11 days of one evening meal did not lower aerobic capacity or strength and raised fat burning during exercise. [2]

  • Lifespan and mortality

    Not enough evidence

    Extends lifespan and boosts autophagy

    Mice fed one meal a day lived longer, but in people eating once a day is linked to higher mortality and fasting did not raise muscle autophagy markers. [12][7][13][14]

Key takeaways

  1. 1

    OMAD means one meal in about one hour and a fast of about 23 hours every day.

  2. 2

    It usually cuts calories, but a single-meal day showed fat loss even without fewer calories in a small trial.

  3. 3

    Controlled trials found higher blood pressure, higher LDL cholesterol and worse morning glucose tolerance than three meals.

  4. 4

    Large US cohorts link eating once a day to higher all-cause and cardiovascular mortality; this does not prove cause.

  5. 5

    Protein is the hardest part: plan a large protein serving and keep strength training.

  6. 6

    If you try it, put the meal earlier in the day and monitor blood pressure, lipids and glucose.

What is OMAD, and how is it different from 16:8?

OMAD is a daily fast of about 23 hours with a single meal. It is the shortest possible daily eating window, so it is a much stronger dose than 16:8, which leaves 8 hours for two or three meals.

OMAD sits at the far end of intermittent fasting. Most fasting schedules either shorten the daily eating window, like time-restricted eating, or cut calories on certain days, like 5:2. OMAD does the first to the extreme: one meal, no snacks, every day.

Because it is so compressed, results from 16:8 trials do not transfer cleanly. A 16-hour fast ends near the start of the metabolic switch; a 23-hour fast spends most of a day beyond it. And fitting a day's food into one sitting changes how protein, glucose and fat are handled.

OMAD compared with other daily and weekly fasting schedules
ScheduleDaily fastMealsControlled trial evidence
OMAD (23:1)About 23 h1One 8-week crossover trial, one 11-day trial
20:420 h1 to 2One 8-week trial of a 4-hour window
16:816 h2 to 3Many trials up to 12 months
5:2None on 5 daysNormal on 5 daysSeveral trials up to 12 months

What happens to your body on one meal a day?

You spend most of each day fasting, burning more fat and feeling hungrier. In controlled trials, one meal a day raised hunger and the hunger hormone ghrelin, lowered cortisol and raised fat burning during exercise.

A single meal sets up a long daily cycle: a large rise in glucose, insulin and fats after the meal, then about 20 hours of falling fuel and rising fat use. Controlled studies show several effects:

  • More fat burning. After 11 days of one 5 to 7 p.m. meal at weight-maintenance calories, lean adults burned more fat during exercise [2].
  • More hunger. Eating one meal a day for 8 weeks significantly raised hunger compared with three meals [1], and raised ghrelin [5].
  • Lower cortisol. The same trial found lower cortisol concentrations on one meal a day [1].
  • A delayed insulin response. With the meal in the evening, the next morning's glucose tolerance test showed higher, longer glucose peaks and a slower insulin response [5].

One idea behind OMAD is that a daily 23-hour fast boosts autophagy, the recycling of worn-out cell parts. Autophagy is hard to measure in people. In one study, repeated 24-hour fasts raised autophagy markers in mouse liver but not in mouse or human muscle [14].

A day on OMAD

Evening
SleepFasting: water, black coffee, plain teaMealFasting: water, black coffee, plain teaSleep
Early
SleepFasting: water, black coffee, plain teaMealFasting: water, black coffee, plain teaSleep
  • Sleep00:00 to 06:30, 22:30 to 00:00
  • Fasting: water, black coffee, plain tea06:30 to 18:00, 19:00 to 22:30, 06:30 to 12:00, 13:00 to 22:30
  • Meal18:00 to 19:00, 12:00 to 13:00

Times are examples; both versions fast for about 23 hours, most of it past the metabolic switch. With an evening meal, trials found worse morning glucose tolerance; an earlier meal fits the body clock better.

Where the single meal and the long fast fall across 24 hours, for evening and early versions.

Does OMAD work for weight loss?

Usually, because one meal is hard to make as large as three. A 4-hour window cut intake by about 550 kcal a day and weight by about 3% in 8 weeks, but no long-term OMAD weight-loss trial exists.

The closest trial to OMAD for weight loss allowed adults with obesity to eat only from 3 to 7 p.m. Without counting calories, they ate about 550 kcal a day less and lost about 3% of body weight in 8 weeks, the same as a 6-hour window [3].

Two small trials gave all weight-maintenance calories in one meal, so calories did not fall:

  • Healthy normal-weight adults kept their weight within 2 kg but lost fat mass on one meal a day for 8 weeks [1].
  • Lean adults on one 5 to 7 p.m. meal for 11 days lost 1.4 kg of body mass, against 0.5 kg on three meals, including 0.7 kg of fat mass [2].

Across trials, eating fewer meals a day lowered weight by 1.85 kg versus control (95% CI 0.13 to 3.55 kg), a small and uncertain effect [15]. An older meta-analysis found that meal frequency itself made little reliable difference to body composition [16]. In 50,660 Adventist adults, people eating one or two meals a day saw their BMI fall slowly over 7 years compared with those eating three [4].

So OMAD can work as a calorie-cutting rule. What is not known is whether people keep it up, or keep the weight off, beyond a few months. One published case lost about 10% of body weight in 3 months on supervised OMAD with exercise [8].

Is OMAD bad for blood sugar, cholesterol or blood pressure?

It can be. In an 8-week controlled trial, one evening meal raised blood pressure and total and LDL cholesterol and worsened morning glucose tolerance compared with three meals of the same calories.

The best controlled data on OMAD come from one US crossover trial that gave the same people one meal or three meals a day for 8 weeks each, at the same calories:

  • Blood pressure rose on one meal a day [1].
  • Total, LDL and HDL cholesterol rose [1]. If you track LDL cholesterol or ApoB, check them after a few months on OMAD.
  • Morning fasting glucose was higher and glucose tolerance worse, with a delayed insulin response [5].

Timing may explain part of this, since the meal was eaten between 4 and 8 p.m. Shorter studies point the same way: in people with type 2 diabetes, skipping breakfast raised the glucose response to lunch by 36.8% and to dinner by 26.6% [6]. In contrast, an 11-day trial of a 5 to 7 p.m. meal in lean adults found lower glucose in the second half of the day [2].

Weight loss can mask these effects. In a published case, a man on supervised OMAD with exercise improved HbA1c and blood pressure as he lost weight, yet his LDL cholesterol rose [8]. The pattern to watch is good weight and glucose numbers with worsening lipids.

Can you keep or build muscle on OMAD?

You can probably keep muscle if the meal has enough protein and you keep training, but OMAD is not the best pattern for building it. Spreading protein over the day built more muscle protein in a controlled study.

Muscle needs protein and training. OMAD puts all of the day's protein in one sitting, and the evidence on that is split:

  • Spread is better in one study. After resistance exercise, 80 g of protein as 20 g every 3 hours built more muscle protein over 12 hours than two 40 g doses [10].
  • Big doses work longer than thought. A single 100 g protein dose produced a larger anabolic response lasting more than 12 hours than a 25 g dose [9]. That weakens the old idea that muscle can use only a modest amount of protein from one meal.
  • Strength held short term. Lean adults on one meal a day for 11 days kept their strength and aerobic capacity [2].

Sports nutrition experts conclude that eating more often may help preserve lean mass in athletes who are dieting, if protein is adequate [11]. For lifters on OMAD, the practical rules are a large protein serving in the meal, a training session a few hours before it, and regular checks of strength and body composition. If strength or muscle drops, a second meal is the simplest fix.

Flat illustration contrasting one large protein portion with the same amount split into four smaller portions.
OMAD puts all of the day's protein in one sitting; studies disagree on how much that matters for muscle.

Is OMAD safe long term?

No one knows, because no long-term trial exists. In a US cohort of 24,011 adults, eating one meal a day was linked to 30% higher all-cause and 83% higher cardiovascular mortality than three meals, which suggests caution but cannot prove cause.

The long-term data on eating once a day are observational:

  • Among 24,011 US adults aged 40 and older followed for about 8 years, eating one meal a day was linked to higher all-cause mortality (hazard ratio 1.30, 95% CI 1.03 to 1.64) and cardiovascular mortality (1.83, 95% CI 1.26 to 2.65) than three meals [7].
  • Among 30,464 US adults, eating fewer than 3 times a day was linked to higher cardiovascular (1.33) and all-cause (1.16) mortality [13].

These studies took eating patterns from one or two days of recall. People who eat once a day may do so because of illness, shift work, poverty or poor appetite, all of which raise mortality. So the link may not be caused by the eating pattern. Still, no study shows the reverse, a lower risk of death, in people.

The longevity case for OMAD comes from mice. Male mice fed one meal a day ate it quickly, fasted the rest of the day and lived longer with less disease, whatever the diet [12]. Mice have far faster metabolisms than people, and a daily fast in a mouse is a much bigger stress. Reviews of fasting regimens, including OMAD, list promising mechanisms but also inconsistent results and weak methods [17].

Eating once a day and mortality in US adults

Show the data
Eating once a day and mortality in US adults
ItemValue (hazard ratio)LowHighNote
Three meals a day (reference)1
One meal a day, all-cause death1.31.031.64
One meal a day, cardiovascular death1.831.262.65
Skipping breakfast vs eating it, cardiovascular death1.41.091.78
Hazard ratios in 24,011 US adults aged 40 and older (NHANES 1999 to 2014). One meal a day is compared with three meals; breakfast skipping with eating breakfast. Values above 1 mean higher risk. Observational data; they cannot show cause. Ranges are 95% confidence intervals.

What should you eat on OMAD, and when?

Eat one large, balanced meal that covers the day's protein, fiber and micronutrients, and if you can, eat it earlier in the day rather than late at night. OMAD sets timing; it does not make low-quality food healthy.

One sitting has to do the work of three. A plan that covers the basics:

Part of the mealWhyExample
A large protein servingMuscle maintenance from one doseFish, chicken, eggs, tofu, Greek yogurt
Two or more vegetablesFiber, potassium, folateLeafy greens, broccoli, peppers
Legumes or whole grainsFiber and steady glucoseLentils, beans, oats, brown rice
Healthy fatsFat-soluble vitamins, satietyOlive oil, nuts, avocado
Fruit or dairyVitamin C, calciumBerries, citrus, milk or kefir

Two timing points come from the trials. The evening meal in the US trial worsened morning glucose tolerance [5], and in people with diabetes, skipping breakfast worsened glucose after later meals [6]. If your schedule allows, a late-morning or early-afternoon meal is the safer choice. Avoid eating your one meal right before bed.

Start gradually. A move through 12-hour, 16:8 and 20:4 windows over several weeks lets you see whether hunger, energy and training cope. Many people find a two-meal pattern gives most of the convenience with fewer downsides; see time-restricted eating for windows of 6 to 10 hours.

The studies, by type

Strongest designs first. Scroll each row; every card links to the paper and says whether it supports the protocol.

Systematic reviews and meta-analyses (2)

  • JAMA Network Open · 2024

    [15]

    Meal Timing and Anthropometric and Metabolic Outcomes: A Systematic Review and Meta-Analysis

    Systematic review and meta-analysis of 29 randomized trials lasting 12 weeks or more · 2,485 adults, mean BMI 33

    In 29 trials of 12 weeks or longer, time-restricted eating lowered weight by 1.37 kg versus control, fewer meals per day by 1.85 kg and eating earlier in the day by 1.75 kg, all small effects from studies at high risk of bias.

    Mixed resultRead
  • Nutrition Reviews · 2015

    [16]

    Effects of meal frequency on weight loss and body composition: a meta-analysis

    Meta-analysis with regression of 15 meal-frequency trials

    Across 15 studies, the apparent body-composition benefit of eating more often rested on a single study, so meal frequency itself made little reliable difference.

    No clear effectRead

Randomized controlled trials (4)

  • American Journal of Clinical Nutrition · 2007

    [1]

    A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults

    Randomized crossover trial, two 8-week periods · Healthy normal-weight middle-aged adults

    Eating all calories in one meal a day for 8 weeks reduced fat mass but raised hunger, blood pressure and total, LDL and HDL cholesterol compared with three meals.

    Mixed resultRead
  • Metabolism · 2007

    [5]

    Impact of reduced meal frequency without caloric restriction on glucose regulation in healthy, normal-weight middle-aged men and women

    Randomized crossover trial, two 8-week periods · Healthy normal-weight middle-aged adults

    One meal eaten between 4 and 8 p.m. raised morning fasting glucose and worsened morning glucose tolerance, with a delayed insulin response, compared with three meals a day.

    Finds againstRead
  • Frontiers in Physiology · 2021

    [2]

    Differential Effects of One Meal per Day in the Evening on Metabolic Health and Physical Performance in Lean Individuals

    Randomized crossover trial, 11 days per arm · 11 healthy lean adults in the Netherlands

    Eating weight-maintenance calories in one 5 to 7 p.m. meal for 11 days lowered body mass by 1.4 kg versus 0.5 kg on three meals and raised fat burning in exercise, without hurting strength or aerobic capacity.

    SupportsRead
  • Cell Metabolism · 2020

    [3]

    Effects of 4- and 6-h Time-Restricted Feeding on Weight and Cardiometabolic Health: A Randomized Controlled Trial in Adults with Obesity

    Randomized trial, 3 arms, 8 weeks · Adults with obesity in Chicago

    Eating only from 3 to 7 p.m. or 1 to 7 p.m. for 8 weeks cut intake by about 550 kcal a day and lowered weight by about 3%, with no difference between the 4-hour and 6-hour windows.

    SupportsRead

Large observational studies in people (3)

  • Journal of the Academy of Nutrition and Dietetics · 2023

    [7]

    Meal Skipping and Shorter Meal Intervals Are Associated with Increased Risk of All-Cause and Cardiovascular Disease Mortality among US Adults

    Prospective cohort (NHANES 1999 to 2014) · 24,011 US adults aged 40 and older

    Among 24,011 US adults aged 40 and older, eating one meal a day was linked to higher all-cause mortality (hazard ratio 1.30) and cardiovascular mortality (1.83) than eating three meals.

    Finds againstRead
  • Journal of Nutrition · 2017

    [4]

    Meal Frequency and Timing Are Associated with Changes in Body Mass Index in Adventist Health Study 2

    Prospective cohort, mean 7.4 years · 50,660 adults in the Adventist Health Study 2

    In 50,660 Adventist adults followed about 7 years, eating 1 or 2 meals a day, a long overnight fast and a large breakfast were each linked to a slow fall in BMI compared with 3 meals.

    SupportsRead
  • International Journal of Behavioral Nutrition and Physical Activity · 2024

    [13]

    Relationship between circadian eating behavior (daily eating frequency and nighttime fasting duration) and cardiovascular mortality

    Prospective cohort (NHANES 2003 to 2014), mortality follow-up to 2019 · 30,464 US adults

    In 30,464 US adults, an overnight fast longer than 14 hours (hazard ratio 1.36) or shorter than 10 hours (1.23) and eating fewer than 3 times a day (1.16) were linked to higher all-cause mortality than a 10 to 11 hour fast.

    Finds againstRead

Mechanistic studies in people (4)

  • Journal of Physiology · 2013

    [10]

    Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis

    Randomized three-group trial with muscle biopsies, 12 hours · 24 trained men

    After resistance exercise, 80 g of protein split into 20 g every 3 hours built more muscle protein over 12 hours than two 40 g doses or eight 10 g doses.

    Finds againstRead
  • Cell Reports Medicine · 2023

    [9]

    The anabolic response to protein ingestion during recovery from exercise has no upper limit in magnitude and duration in vivo in humans

    Randomized trial with quadruple isotope tracers, 12 hours

    A single 100 g protein dose after exercise produced a larger and longer muscle-building response, lasting more than 12 hours, than a 25 g dose.

    SupportsRead
  • Diabetes Care · 2015

    [6]

    Fasting until noon triggers increased postprandial hyperglycemia and impaired insulin response after lunch and dinner in individuals with type 2 diabetes: a randomized clinical trial

    Randomized crossover trial, two test days · 22 adults with type 2 diabetes in Israel

    In type 2 diabetes, skipping breakfast raised the glucose response to the same lunch by 36.8% and to dinner by 26.6%, with lower and later insulin.

    Finds againstRead
  • Nutrition · 2022

    [14]

    Intermittent fasting activates markers of autophagy in mouse liver, but not muscle from mouse or humans

    Mouse experiment plus muscle biopsies from a randomized trial, 8 weeks · 50 women with overweight, mean age 51, and mice

    Repeated 24-hour fasts raised autophagy markers in mouse liver but not in mouse muscle, and in women's thigh muscle several markers fell rather than rose after 8 weeks of fasting with weight loss.

    Finds againstRead

Animal and cell studies (1)

  • Cell Metabolism · 2019

    [12]

    Daily Fasting Improves Health and Survival in Male Mice Independent of Diet Composition and Calories

    Mouse lifespan study · Male mice

    Male mice fed one meal a day ate quickly, fasted the rest of the day and lived longer with less disease than mice with constant access to food, whatever the diet.

    SupportsRead

Case reports and N-of-1 experiments (1)

  • Journal of Family Medicine and Primary Care · 2025

    [8]

    Management of prediabetes and class III obesity in a 42-year-old male through One-Meal-a-Day

    Case report, 3 months · One 42-year-old man with class III obesity and prediabetes

    A man with a BMI near 40 and prediabetes lost about 10% of his weight in 3 months on supervised one meal a day plus exercise, with better HbA1c and blood pressure but higher LDL cholesterol.

    Mixed resultRead

Hypotheses and expert reviews (2)

  • Journal of the International Society of Sports Nutrition · 2011

    [11]

    International Society of Sports Nutrition position stand: meal frequency

    Expert position stand

    This position stand concludes that eating more often does not change body composition in sedentary people but may help preserve lean mass in dieting athletes and control hunger.

    Finds againstRead
  • European Journal of Clinical Nutrition · 2026

    [17]

    Intermittent fasting: Impact, mechanisms and cautions across medical and lifestyle domains

    Narrative review

    This review groups OMAD with 16:8, 5:2 and alternate-day fasting, describes the nutrient-sensing pathways fasting acts on, and flags inconsistent findings and weak methods.

    Mixed resultRead

Who follows it, who backs it, who doubts it

Public positions summarized in our words. Follow each link for the full context.

Follow it

  • Jack DorseyCofounder of Twitter and Block

    Said on the Ben Greenfield Fitness podcast that he eats one meal a day on weekdays, typically protein with green vegetables and berries or dark chocolate, and sometimes goes three days on water only.

    The Takeout, April 2019

  • Herschel WalkerFormer NFL running back and MMA fighter

    Has eaten one meal a day since he was a junior in high school, a habit he kept through college football, the NFL and his MMA career.

    Bleacher Report, November 2015

Support it

Mixed or cautious

  • Gil CarvalhoPhysician and neuroscientist, Nutrition Made Simple!

    Sees OMAD as a simple way to cut calories for healthy people but warns that fasting does not fix a poor diet, that nutrient needs are hard to meet in one meal and that an evening meal may worsen glucose; he would eat the meal in the morning or early afternoon.

    Doctor Reviews OMAD (One Meal a Day), YouTube

Oppose or doubt it

Public examples

How to follow it

  1. Do not start from three meals. Move through a 12-hour window, then 16:8, then 20:4 over several weeks, and stop at the step that works for you.
  2. Choose a meal time you can keep every day. An earlier meal, late morning to mid-afternoon, fits the body clock better than a late dinner.
  3. Build the meal around protein first, then vegetables, legumes or whole grains, fruit and healthy fats, so one sitting covers the day.
  4. Check the meal in a nutrition tracker for a week to see whether it meets protein, fiber, calcium, iron and other needs.
  5. Drink water through the fast. Black coffee and plain tea are fine; milk, sugar and juice break the fast.
  6. Keep resistance training two or more times a week, ideally a few hours before the meal.
  7. If you take any medication with food, or for diabetes or blood pressure, agree a plan with your clinician first.

How to know you are following it

Log the start and end time of the meal; a day counts when all calories fall inside about one hour. Count OMAD days per week. Track weight weekly and waist monthly. Because the trial signals were higher blood pressure, LDL cholesterol and morning glucose, check blood pressure weekly and repeat a lipid panel and HbA1c or fasting glucose after about 8 to 12 weeks.

Common mistakes

  • Treating the meal as unlimited: OMAD is often marketed as eating whatever you want in the hour, which undoes its benefits.
  • Missing protein, fiber and micronutrients that are hard to fit into one sitting.
  • Eating the one meal late at night, close to sleep.
  • Jumping from three meals to OMAD overnight and rebounding into binge eating.
  • Training hard on an empty tank without planning when to refuel.

Who should be careful

Check with a clinician first if you

  • You are pregnant, breastfeeding or trying to conceive.
  • You have had an eating disorder, or fasting triggers bingeing.
  • You are under 18, underweight or an older adult at risk of muscle loss.
  • You take insulin, sulfonylureas or SGLT2 inhibitors: check with your clinician first.
  • You have high blood pressure, high LDL cholesterol or heart disease: check with your clinician first, since trials saw both rise.
  • You take medication that must be taken with food two or three times a day.

Possible side effects

  • Strong hunger, especially in the first weeks; hunger stayed higher than on three meals in a controlled trial.
  • Higher blood pressure and LDL cholesterol in some people.
  • Worse morning glucose tolerance when the meal is in the evening.
  • Fatigue, poor concentration or dizziness late in the fast.
  • Indigestion, reflux or discomfort from one very large meal.
  • Nutrient shortfalls if the meal is not planned.

Watch

Talks and explainers worth your time. Nothing loads from YouTube until you press play.

  • Doctor Reviews OMAD (One Meal a Day)

    Nutrition Made Simple!Open on YouTube

    A physician-scientist weighs the simplicity of OMAD against nutrient and glucose concerns, without hype in either direction.

  • One Meal a Day (OMAD) and your Health. [Study 18, 144-146 Analysis]

    PhysionicOpen on YouTube

    A detailed walk through the controlled one-meal-a-day trial data, including the blood pressure and body fat findings.

  • JASON FUNG 5’ | FASTING: 16x8 or OMAD. Easy to fit into family; friends lifestyle

    DoctorsToTrustOpen on YouTube

    A short clip of the best-known OMAD advocate explaining how he fits 16:8 or OMAD around family and social life.

Biomarkers it can move

Common questions

Is OMAD healthy?

It is not proven healthy or unhealthy over the long term. Short controlled trials show fat loss but also higher blood pressure, higher LDL cholesterol and worse morning glucose tolerance, and observational studies link eating once a day to higher mortality.

Is OMAD better than 16:8?

There is no head-to-head trial. 16:8 has far more evidence, including trials up to a year, and leaves room for two or three meals with enough protein. OMAD cuts calories harder but has more reported downsides.

Can you do OMAD every day?

Many people do, but daily OMAD has been studied for only 8 weeks at a time in controlled trials. Part-time OMAD, two or three days a week, is a gentler option.

What is the best time to eat on OMAD?

Evidence favors earlier in the day. An evening meal worsened morning glucose tolerance in a controlled trial, and breakfast skipping raised glucose after later meals in people with diabetes. Late morning to mid-afternoon is a reasonable choice.

Does OMAD cause muscle loss?

Not necessarily. Strength held over 11 days in one trial, and a large protein dose can build muscle for over 12 hours. But spreading protein across meals built more muscle in another study, so lifters need a big protein serving and regular checks.

How much weight can you lose on OMAD?

It varies. A 4-hour eating window led to about 3% weight loss in 8 weeks in adults with obesity. Long-term results are unknown, and weight returns if eating habits revert.

Does OMAD increase autophagy?

It has not been shown in people. Fasting raised autophagy markers in mouse liver, but not in human muscle in one study, and there is no reliable blood test for autophagy.

Can you drink coffee on OMAD?

Yes, black coffee, plain tea, water and other zero-calorie drinks are allowed during the fast. Milk, sugar, juice and alcohol count as food.

Can OMAD lower cholesterol?

Usually not. In a controlled trial, total and LDL cholesterol rose on one meal a day compared with three, and a published case saw LDL rise despite weight loss. Recheck lipids if you try it.

Sources

  1. 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. American Journal of Clinical Nutrition, 2007. doi:10.1093/ajcn/85.4.981
  2. 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. Frontiers in Physiology, 2021. doi:10.3389/fphys.2021.771944
  3. 3.Cienfuegos S, Gabel K, Kalam F, 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. doi:10.1016/j.cmet.2020.06.018
  4. 4.Kahleova H, Lloren JI, Mashchak A, et al. Meal Frequency and Timing Are Associated with Changes in Body Mass Index in Adventist Health Study 2. Journal of Nutrition, 2017. doi:10.3945/jn.116.244749
  5. 5.Carlson O, Martin B, Stote KS, et al. Impact of reduced meal frequency without caloric restriction on glucose regulation in healthy, normal-weight middle-aged men and women. Metabolism, 2007. doi:10.1016/j.metabol.2007.07.018
  6. 6.Jakubowicz D, Wainstein J, Ahren B, et al. Fasting until noon triggers increased postprandial hyperglycemia and impaired insulin response after lunch and dinner in individuals with type 2 diabetes: a randomized clinical trial. Diabetes Care, 2015. doi:10.2337/dc15-0761
  7. 7.Sun Y, Rong S, Liu B, et al. Meal Skipping and Shorter Meal Intervals Are Associated with Increased Risk of All-Cause and Cardiovascular Disease Mortality among US Adults. Journal of the Academy of Nutrition and Dietetics, 2023. doi:10.1016/j.jand.2022.08.119
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