Fasting Tracker

Fasting plans

OMAD vs 16:8: which is better?

One meal a day or an 8-hour window: what the evidence shows, and what it doesn't

OMAD and 16:8 side by side

OMAD and 16:8 compared
16:8OMAD
Fast16 h23 h
Eating window8 h1 h
MealsTwo or threeOne
Level in Fasting TrackerIntermediateAdvanced
Stage when the fast endsFat Burning, just begunFat Burning, an hour before Ketosis
Protein for 110 g a dayAbout 37 g a meal over three meals110 g in one meal
EvidenceSeveral randomized trialsOne small pilot trial
In Fasting TrackerFreePro

What the research shows

16:8 has been studied the most of any daily plan. On its own, without other changes, it didn't beat three meals a day for weight in a 12-week trial of 116 adults 2. With strength training and enough protein, it kept muscle and strength in trained men and women 3,4. The lesson: it helps mainly by making it easier to eat less, and works best alongside protein and exercise.

OMAD is a different story. We haven't found a well-designed weight-loss trial of OMAD among the studies behind Fasting Tracker's guides, so be wary of anyone who promises specific results. The closest test is an older one:

Key study

One meal a day, same calories

  • Randomized crossover pilot
  • Healthy, normal-weight adults
  • 8 weeks on each pattern

People ate all the calories they needed in either one meal or three meals a day. On one meal they lost a little fat, but they were hungrier, and their blood pressure and total, LDL and HDL cholesterol rose.

Stote et al., Am J Clin Nutr 2007

It was a small pilot study in people without obesity, and it kept calories the same on purpose, so it can't tell you how OMAD works for weight loss. The nearest evidence for that is a 4-hour window, which led to about 3% weight loss in 8 weeks, mostly because people ate less 5.

Protein: one meal or several?

Your body can use more protein from one meal than the old "30 g limit" suggests. When researchers followed labelled protein after a workout, a 100 g dose kept building muscle for more than 12 hours, and very little was simply burned off 6. But when trained men had 80 g of protein after exercise, four servings of 20 g built more muscle over 12 hours than eight small ones or two large ones 7.

So one meal can carry your protein, but two or three meals do it a little better, and 16:8 leaves room for them. If you train or want to keep muscle while you lose weight, that's a real point in 16:8's favour 8. See protein and muscle for more.

Which one can you keep?

A plan only works if you keep doing it 9. A few things to weigh:

  • Hunger: one meal a day made people hungrier in the pilot trial 1. Hunger on a fast tends to come in waves at your usual meal times and pass 10, but on OMAD there are more of them.
  • Nutrients: fitting enough protein, fibre, fruit and vegetables into one sitting takes planning.
  • Social life: 16:8 leaves room for a shared breakfast or lunch; OMAD often means sitting out a meal.
  • Flexibility: many people do 16:8 most days and OMAD only now and then.

Moving from 16:8 to OMAD

  1. Get comfortable with 16:8 first, then 18:6 and 20:4.
  2. Try OMAD on one or two days a week rather than every day.
  3. Make the meal large and balanced: protein first, plenty of vegetables, then starches 11.
  4. Drink water through the day, with a pinch of salt if you get a headache or feel lightheaded 12.
  5. Stop and eat if you feel dizzy, shaky or unusually weak.

In Fasting Tracker, 16:8 is free; OMAD and 20:4, the step between them, come with Pro.

Sources

  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):981-8. doi.org/10.1093/ajcn/85.4.981
  2. Lowe DA, Wu N, Rohdin-Bibby L, et al. Effects of Time-Restricted Eating on Weight Loss and Other Metabolic Parameters in Women and Men With Overweight and Obesity: The TREAT Randomized Clinical Trial. JAMA Intern Med. 2020;180(11):1491-1499. doi.org/10.1001/jamainternmed.2020.4153
  3. Moro T, Tinsley G, Bianco A, et al. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. J Transl Med. 2016;14(1):290. doi.org/10.1186/s12967-016-1044-0
  4. Tinsley GM, Moore ML, Graybeal AJ, et al. Time-restricted feeding plus resistance training in active females: a randomized trial. Am J Clin Nutr. 2019;110(3):628-640. doi.org/10.1093/ajcn/nqz126
  5. 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 Metab. 2020;32(3):366-378.e3. doi.org/10.1016/j.cmet.2020.06.018
  6. Trommelen J, van Lieshout GAA, Nyakayiru J, et al. The anabolic response to protein ingestion during recovery from exercise has no upper limit in magnitude and duration in vivo in humans. Cell Rep Med. 2023;4(12):101324. doi.org/10.1016/j.xcrm.2023.101324
  7. Areta JL, Burke LM, Ross ML, et al. Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis. J Physiol. 2013;591(9):2319-31. doi.org/10.1113/jphysiol.2012.244897
  8. Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018;52(6):376-384. doi.org/10.1136/bjsports-2017-097608
  9. Patikorn C, Roubal K, Veettil SK, et al. Intermittent Fasting and Obesity-Related Health Outcomes: An Umbrella Review of Meta-analyses of Randomized Clinical Trials. JAMA Netw Open. 2021;4(12):e2139558. doi.org/10.1001/jamanetworkopen.2021.39558
  10. Natalucci G, Riedl S, Gleiss A, et al. Spontaneous 24-h ghrelin secretion pattern in fasting subjects: maintenance of a meal-related pattern. Eur J Endocrinol. 2005;152(6):845-50. doi.org/10.1530/eje.1.01919
  11. Leidy HJ, Clifton PM, Astrup A, et al. The role of protein in weight loss and maintenance. Am J Clin Nutr. 2015;101(6):1320S-1329S. doi.org/10.3945/ajcn.114.084038
  12. Sigler MH. The mechanism of the natriuresis of fasting. J Clin Invest. 1975;55(2):377-87. doi.org/10.1172/JCI107941
  13. Grajower MM, Horne BD. Clinical Management of Intermittent Fasting in Patients with Diabetes Mellitus. Nutrients. 2019;11(4):873. doi.org/10.3390/nu11040873

A note on health

Fasting Tracker is designed for general wellness and is not a medical device. Fasting is not right for everyone. If you are pregnant, diabetic, have a history of eating disorders or take medication, talk to your doctor first, and before any extended fast.