This is not medical advice. General information about meal timing for self-tracking, not a treatment plan or a reason to eat less. If you are under 18, pregnant or breastfeeding, have ever had an eating disorder or a difficult relationship with food, take insulin or another medicine for diabetes, or are managing a medical condition, talk to a doctor or a registered dietitian before you change when or how much you eat. The full list is here.

Most advice about when to eat comes with a mechanism attached: eat with your body clock, keep insulin down in the evening, get your metabolism going with breakfast. A few of those mechanisms have been measured, and some of the measurements are real. The question for someone already counting calories is narrower than any of them: once the day's total is fixed, does moving it around the clock change what the scale does?

That narrower question has been tested in randomised trials, several of them in the last six years, and the answer is less exciting than the headlines and more useful. I have tried to report each one at the size it actually found, with the limits its authors gave it.

Two neighbouring questions have their own posts. What goes into the daily total in the first place is how to count calories. Restricting by the fortnight rather than by the hour, the diet-break trials, is in why a weight loss plateau is usually not your metabolism. This one is only about the clock.

Why meal timing is usually a calorie question in disguise

When people change when they eat, they nearly always change how much. Skip breakfast and, unless you make it up later, you ate less. Close the kitchen at eight and the evening snacks go with it. So a study that lets people eat freely inside a window and finds the window works has not shown that the clock matters. It may only have shown that a window is a way of eating less.

A 2023 trial in Chicago shows this about as plainly as it can be shown. Ninety adults with obesity were randomised for 12 months to eat only between noon and 8 pm without counting anything, to cut calories by 25% a day, or to carry on eating over ten or more hours. The window group cut 425 kcal a day on average and the counting group 405. Against the controls, the window group lost 4.61 kg and the counting group 5.42 kg, and the difference between those two, 0.81 kg, was not significant (95% CI -3.07 to 4.69).1 The authors list their own limits: participants were not blinded, the trial was "not powered to detect relatively large differences in weight loss", and there was no adjustment for multiple comparisons.1

Read that as two routes to the same deficit. The window did roughly what a calorie count did because it produced roughly the same calorie cut.

The TREAT trial ran the comparison the other way. It randomised 116 adults to a 16:8 window, eating freely from noon to 8 pm, or to three structured meals a day, for 12 weeks. The difference in weight between groups was -0.26 kg (95% CI -1.30 to 0.78), estimated energy intake did not differ, and the authors concluded that time-restricted eating "in the absence of other interventions, is not more effective in weight loss than eating throughout the day."2 In the 50 participants tested in person, the window group also lost more appendicular lean mass, the muscle in the arms and legs, than the meals group.2 That is a secondary outcome in a small subgroup, and I would not build anything on it, but it points the opposite way from what most people want from a window.

So the trials that tell you something about the clock itself are the ones that hold the calories steady: either they feed both groups the same amount, or they give both groups the same calorie target and then change only the timing.

Time-restricted eating when both groups counted calories

The cleanest test of the question in this post is a year-long trial from Guangzhou, published in 2022. It put 139 adults with obesity on the same calorie-restricted diet for 12 months, 1,500 to 1,800 kcal a day for men and 1,200 to 1,500 for women, and told half of them to eat only between 8 am and 4 pm. Of the 139, 118 (84.9%) finished.3

The window group lost 8.0 kg and the calorie-restriction group 6.3 kg. The net difference, -1.8 kg, had a 95% confidence interval from -4.0 to 0.4 and was not significant (P = 0.11). Waist, BMI, body fat, lean mass, blood pressure and the metabolic markers all told the same story, and the authors concluded that time-restricted eating "was not more beneficial with regard to reduction in body weight, body fat, or metabolic risk factors than daily calorie restriction."3

Not significant is not the same as zero, and I think it is worth being precise about what this trial rules out. Its best guess favours the window by 1.8 kg over a year. Its interval runs from 4 kg better to 0.4 kg worse. It rules out a large advantage for eating early. It does not rule out a modest one.

A second trial, from Alabama in the same year, found something closer to that modest one. Ninety adults with a mean BMI of 39.6, 80% of them women, all received the same weight-loss treatment with calorie restriction for 14 weeks. They were randomised to eat between 7 am and 3 pm, or over a window of 12 hours or more. The early-window group kept to it 6.0 days a week on average and lost 2.3 kg more (95% CI -3.7 to -0.9). Body fat did not differ significantly (-1.4 kg, 95% CI -2.9 to 0.2), nor did the share of the loss that was fat. The authors put the effect as "equivalent to reducing calorie intake by an additional 214 kcal/d".4

The same abstract reports that food intake was similar between the groups.4 So either the window did something worth about 214 kcal a day beyond the calories, or the method used to measure intake missed a gap of about that size. That method was a photograph-based one, the Remote Food Photography Method, and the paper discloses that one author is an inventor of it and that his institution holds an interest in it.4 I make a photo-based calorie estimator for a living, so I am the last person to call that method crude. But a 214 kcal daily gap is well inside what any intake estimate can miss, and I cannot tell you from this trial which reading is right.

Put the two trials side by side. Both used an early window, both counted calories in both arms, and one found 2.3 kg over 14 weeks while the other found a non-significant 1.8 kg over a year. That is consistent with a small effect that is hard to detect, and also with no effect at all.

Big breakfast or big dinner, same calories

The other way to test the clock is to keep the meals and move the calories between them. The trial everyone quotes is from Israel, 2013. Women with overweight or obesity and metabolic syndrome, mean BMI 32.4, were put on about 1,400 kcal a day for 12 weeks, split either 700 at breakfast, 500 at lunch and 200 at dinner, or the same numbers reversed. The big-breakfast group lost more weight and more waist, their triglycerides fell 33.6% while the dinner group's rose 14.6%, and their hunger scores were lower.5 The abstract gives the direction of the weight difference but not its size, so I am not going to quote a figure for it.

A 2022 trial in Aberdeen was designed to find out why. Thirty adults with overweight or obesity did two four-week weight-loss diets with identical calories, in random order: 45%, 35% and 20% of the day at breakfast, lunch and dinner, or 20%, 35% and 45%. The finding, in the authors' words: "no differences in total daily energy expenditure or resting metabolic rate related to the timing of calorie distribution, and no difference in weight loss." The morning-loaded diet did produce significantly lower hunger, and the authors suggest a big breakfast "may assist with compliance to weight loss regime through a greater suppression of appetite."6

That result sits awkwardly next to a well-known lab finding. In a German crossover, 16 normal-weight men spent three days in the laboratory eating a small breakfast (11% of their daily need) and a large dinner (69%), then the reverse. The energy spent digesting food was 2.5 times higher after the morning meal than after the evening one, whether the meal was large or small, and the small-breakfast condition left them hungrier through the day, with more appetite for sweets.7 I believe both results. A bigger burn after one meal is not the same thing as a bigger burn across the day, and when Aberdeen measured the whole day for four weeks it found no difference.

A 2022 Boston study came at it from the other side, with food, activity, sleep and light exposure all tightly controlled, and compared the same meals eaten early or late. Eating late raised hunger, shifted the appetite hormones (the waking and 24-hour ratio of ghrelin to leptin went up), lowered waking energy expenditure and 24-hour core body temperature, and changed gene expression in fat tissue in a direction the authors read as favouring fat storage. Their conclusion is careful: these are "converging mechanisms by which late eating may result in positive energy balance and increased obesity risk."8 Note the "may". The study reports hunger, hormones, energy expenditure and fat tissue, and it was not a weight-loss trial.

Across those four, one finding keeps turning up, and it is hunger. Moving calories earlier lowered it in Israel and Aberdeen, a small breakfast raised it in Germany, and eating late raised it in Boston. Whether timing changes the energy you burn is contested. Whether it changes the weight you lose, with calories held equal, came out yes in one 12-week trial and no in one four-week crossover. The hunger effect is the one you can use.

Skipping breakfast while counting calories to lose weight

In observational studies, people who eat breakfast tend to weigh less, and public health bodies have long recommended it to reduce obesity.9 A 2014 trial tested the advice itself. It randomised 309 adults with a BMI of 25 to 40, who were trying to lose weight, to be told to eat breakfast, told to skip it, or given no instruction, for 16 weeks, and it balanced the groups by whether people already ate breakfast.9

283 finished. People did what they were told, with self-reported compliance of 93.6% in the breakfast group and 92.4% in the skipping group, and it made no difference to their weight. Every group, breakfast habit or not, lost somewhere between about half and three-quarters of a kilo. The authors: the recommendation "had no discernable effect on weight loss in free-living adults who were attempting to lose weight."9

A 2019 BMJ meta-analysis pooled 13 randomised trials from high-income countries. The weight difference slightly favoured the people who skipped breakfast, by 0.44 kg (95% CI 0.07 to 0.82), and the people assigned to eat breakfast ate about 260 kcal a day more in total.10 The authors are frank about the evidence: every included trial was at high or unclear risk of bias in at least one domain, follow-up averaged seven weeks for weight, and "as the quality of the included studies was mostly low, the findings should be interpreted with caution."10

For anyone using a calorie counter app, the 260 kcal matters more than the 0.44 kg. The breakfast in those trials was added on top of whatever else people ate. A daily budget does not work that way: breakfast comes out of the same total as everything else, so it can only cost you if it makes you eat more later, and your log will show you whether it does.

If you are wondering how that fits with the big-breakfast trials above, the difference is what was being compared. Aberdeen and Israel moved calories to the morning inside a fixed total. The breakfast trials added or removed a meal and let the total float. Both can be true at once.

What the evidence does not settle

The evidence most often quoted for eating early is not a trial. A 2013 Spanish study followed 420 people through a 20-week weight-loss programme and split them by when they ate their main meal, which in that population is lunch. Those who ate it after 3 pm lost less weight, and more slowly, than those who ate earlier, even though energy intake, diet composition, estimated energy expenditure, appetite hormones and sleep were all similar. But the late eaters were also more often evening types, ate smaller breakfasts and skipped breakfast more often.11 A study like this cannot separate the clock from the kind of person who eats late, and the authors' conclusion is appropriately soft: eating late "may influence" the success of weight-loss therapy.

Beyond that, four gaps I would want flagged if I were the one reading.

  • The trials that found an effect of timing were short: 14 weeks in Alabama and 12 in Israel. The two that ran for a year, in Guangzhou and Chicago, found no significant difference between a window and a calorie count.13
  • Whether a window changes what the lost weight is made of is open. TREAT saw more lean mass lost in a subgroup of 50,2 and the Alabama trial saw no significant difference in body fat in its main analysis.4
  • The mechanism studies are small and brief. The German thermogenesis finding comes from 16 normal-weight men over three days,7 which is a long way from anyone trying to lose weight over months.
  • Every window in these trials is set by the clock: 7 to 3, 8 to 4, noon to 8. None of them was designed around people who sleep in the day, so if you work nights, there is no trial here that answers your version of the question.

What a meal tracker app can see about timing, and what it cannot

I can only speak for my own app here. MyPlate stores the time of every meal as well as the day, and when you edit a meal you can change both. The day decides which daily total the meal counts toward and the time only decides its place in that day's list. It does not chart when you eat, set an eating window or run a fasting timer, and I have no plans to add one on the strength of the evidence above.

Two consequences worth knowing. The day ends at midnight, so if you work nights, a meal at 2 am on a shift that started the evening before lands on the next day's total. The weekly average is unaffected, but individual days look lumpy, and it is weeks rather than days you should be comparing anyway. And the time of day does not change a scan: the estimate for a plate at 8 in the morning is the same as for the same plate at 8 at night, which is right, because nothing above says the calories in a meal change with the clock.

What the timestamps are good for is testing the one effect that held up. If your log keeps showing a light lunch followed by a 4 pm raid on the biscuit tin, you have the evidence you need to try moving calories earlier, and a month of the same log will show whether it helped you track meals at your target more often.

How to use meal timing if you count calories

Set the total first. Every trial above that held calories steady found timing to be, at most, a small addition to them. The total also has a floor: MyPlate will not show a daily target below 1,200 kcal for women or 1,500 for men, a limit taken from the NIH clinical guidelines on obesity.12 A shorter eating window is never a reason to go under it.

Then place the calories where the hunger is. If evenings are where your day goes wrong, move some of the budget to breakfast and lunch for four weeks and see whether the evenings get easier. That is the effect the Aberdeen trial found, and it is about sticking to the number rather than beating it.6

If an eating window makes it easier to stay under the total, use it. In the Chicago trial it cut about as many calories as counting did.1 If it leaves you ravenous at the end of the window and eating the difference back, drop it, because on the year-long evidence you are giving up nothing measurable.3 The same goes for breakfast in either direction.

Judge any change on the weight trend over at least four weeks. A single week tells you almost nothing, and what a stalled trend does and does not mean is in the plateau post.

One limit on all of this. If you find yourself pushing meals later and later to "save" calories, or skipping them and then feeling you have to earn the next one, that is not meal timing any more. Stop and talk to a doctor or a registered dietitian. What the research says about who is most at risk is in can calorie tracking cause an eating disorder.

Common questions

Does meal timing matter if you count calories?

Not much, as far as the trials can tell. In a 12-month trial where both groups ate the same restricted calories, adding an 8 am to 4 pm eating window gave a net difference of 1.8 kg that was not statistically significant, with a confidence interval running from 4.0 kg better to 0.4 kg worse.3 A shorter 14-week trial with calorie restriction in both arms found an early window added 2.3 kg of loss, though body fat did not differ significantly.4 The total decides most of the result, and timing is at most a small addition to it.

Is it bad to eat late at night when counting calories to lose weight?

Not for the calorie count itself, but it may make the count harder to keep. In a tightly controlled laboratory study, eating the same food later raised hunger and lowered waking energy expenditure, and the authors say this "may" lead to weight gain.8 A four-week trial that moved calories from breakfast to dinner inside the same total found no difference in energy expenditure or weight loss, only more hunger.6 Studies that link late eating to worse weight loss are observational, and the late eaters in them differed in other ways too.11

Does intermittent fasting work better than counting calories?

No better, in the year-long trials. A 12-month trial found eating between noon and 8 pm without counting cut about 425 kcal a day and a 25% calorie restriction cut about 405, and the weight loss did not differ significantly between the two, though the authors note the trial was not powered to detect relatively large differences.1 Another 12-month trial found that adding an eating window to calorie restriction did not significantly improve weight loss.3 An eating window is a reasonable way to eat less if it suits you. It is not a way around eating less.

Should I eat breakfast to lose weight?

Only if it helps you eat less across the whole day. A 16-week trial of 309 adults told to eat breakfast, skip it, or do neither found no effect on weight loss.9 A meta-analysis of 13 trials found a small difference favouring skippers, 0.44 kg, and about 260 kcal a day more eaten by the breakfast groups, though its authors rated the trials mostly low quality and short.10 If you track against a daily total, breakfast comes out of the same budget as everything else, so eat it if it keeps you less hungry later and skip it if it does not.

What should a meal tracker app record about meal timing?

The time of each meal, and a way to correct it when you log late. That is enough to see whether your hunger follows a pattern, which is the one timing effect the trials keep finding.6 MyPlate records the time of every meal and lets you edit it, but it has no fasting timer and does not chart when you eat, so if you want a timer, a dedicated fasting app does that and a calorie log does the rest. Check too where an app ends the day, because a midnight cut-off splits a night shift across two daily totals.

Put the calories where the hunger is

If you are counting calories to lose weight, the clock is a second-order question. The trials that held calories steady found timing added nothing significant over a year, or a couple of kilos over a few months, and the one effect that turned up in almost every study was hunger rather than burn.346

So fix the total, keep it above the floor, and then arrange the day around when you find it hardest to stick to. An early window, a big breakfast, or three ordinary meals are all defensible, and the right one is whichever you can still be doing in two months.

Sources

Every figure above traces to one of these. If you find a number that doesn't match the source it claims, tell me and I'll correct it.

  1. Lin S, Cienfuegos S, Ezpeleta M, et al. (2023). Time-Restricted Eating Without Calorie Counting for Weight Loss in a Racially Diverse Population: A Randomized Controlled Trial. Annals of Internal Medicine, 176(7):885-895. Read on PubMed →
  2. Lowe DA, Wu N, Rohdin-Bibby L, et al. (2020). 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 Internal Medicine, 180(11):1491-1499. Read on PubMed →
  3. Liu D, Huang Y, Huang C, et al. (2022). Calorie Restriction with or without Time-Restricted Eating in Weight Loss. New England Journal of Medicine, 386(16):1495-1504. Read on PubMed →
  4. Jamshed H, Steger FL, Bryan DR, et al. (2022). Effectiveness of Early Time-Restricted Eating for Weight Loss, Fat Loss, and Cardiometabolic Health in Adults With Obesity: A Randomized Clinical Trial. JAMA Internal Medicine, 182(9):953-962. Read on PubMed →
  5. Jakubowicz D, Barnea M, Wainstein J, Froy O (2013). High caloric intake at breakfast vs. dinner differentially influences weight loss of overweight and obese women. Obesity, 21(12):2504-2512. Read on PubMed →
  6. Ruddick-Collins LC, Morgan PJ, Fyfe CL, et al. (2022). Timing of daily calorie loading affects appetite and hunger responses without changes in energy metabolism in healthy subjects with obesity. Cell Metabolism, 34(10):1472-1485.e6. Read on PubMed →
  7. Richter J, Herzog N, Janka S, et al. (2020). Twice as High Diet-Induced Thermogenesis After Breakfast vs Dinner On High-Calorie as Well as Low-Calorie Meals. Journal of Clinical Endocrinology & Metabolism, 105(3):dgz311. Read on PubMed →
  8. Vujović N, Piron MJ, Qian J, et al. (2022). Late isocaloric eating increases hunger, decreases energy expenditure, and modifies metabolic pathways in adults with overweight and obesity. Cell Metabolism, 34(10):1486-1498.e7. Read on PubMed →
  9. Dhurandhar EJ, Dawson J, Alcorn A, et al. (2014). The effectiveness of breakfast recommendations on weight loss: a randomized controlled trial. American Journal of Clinical Nutrition, 100(2):507-513. Read on PubMed →
  10. Sievert K, Hussain SM, Page MJ, et al. (2019). Effect of breakfast on weight and energy intake: systematic review and meta-analysis of randomised controlled trials. BMJ, 364:l42. Read on PubMed →
  11. Garaulet M, Gómez-Abellán P, Alburquerque-Béjar JJ, et al. (2013). Timing of food intake predicts weight loss effectiveness. International Journal of Obesity, 37(4):604-611. Read on PubMed →
  12. National Heart, Lung, and Blood Institute, NIH (1998). Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. NIH Publication 98-4083. Read the guidelines →

The formulas and limits behind MyPlate's own numbers, with their citations, are on the health sources page.