Early Vs Late-Night Eating: Contradictions, Confusions, And Clarity

early vs late eating intermittent fasting

Is our experience of the world, including the encompassing health effects of what we eat, pre-determined by timing? 

Humans display a definitive rhythm of metabolic and appetite-related hormones. These rhythms appear in all parts of the body – including the pancreas, liver, and even body fat cells – and are primarily controlled by a part of the hypothalamus known as the suprachiasmatic nucleus (SCN). External factors, known as “zeitgebers,” can affect these rhythms as well, a primary one being meal timing. The evolution of the natural timing of these hormones would indicate that certain times of day may be more suited to eating than others, while deviations from these rhythms may encourage metabolic issues. Indeed, when rodents eat during the day (when, as nocturnal creatures, they normally are asleep), they can experience disruptions in their circadian clocks and metabolic issues. 

But how does this pan out in humans, particularly when it comes to the increasing popularity of intermittent fasting? Also known as “time-restricted eating,” this pattern of eating mandates eating all of one’s daily calories within a limited daily time window, the self-selected timing of which may be early in the day, late at night, or anywhere in between.  

CIRCADIAN HORMONAL RHYTHMS 

The 2021 Nutrients study, Beneficial Effects of Early Time-Restricted Feeding on Metabolic Diseases: Importance of Aligning Food Habits with the Circadian Clock, evaluates the role of hormones in our circadian rhythms, with particular regard to their relation to time-restricted eating windows either in the morning or evening. (While the study provides a great deal of insight, I do take pause with some of their logic, which seemingly skews toward an inherent bias for early eating, and is even contradictory at points to support this agenda.)

According to the study, cortisol peaks in the early morning. A catabolic hormone often associated with the fasted state, cortisol actually can encourage the release of all fuel substrates into the bloodstream: fatty acids, glucose, and even amino acids. It would seem to me, then, that a period of naturally high cortisol would indicate the body is accustomed to generating energy endogenously, rather than taking in a meal, and early morning would thus not be a good time to eat (despite the study concluding the exact opposite.)

Up next we’ve got adiponectin, a hormone which promotes burning fat and carbs, and which – according to the study - is secreted between 10 a.m. to 9 p.m., and peaks at 11 a.m. Interestingly, studies have found adiponectin correlates to eating disinhibition, but not eating restraint or hunger. These mixed eating behavior reactions, coupled with the hormone’s ability to promote burning fat and carbs, would argue that nuance may be needed to determine if adiponectin is best suited to burning fuel from a meal or from a fast. I therefore agree with the study’s conclusion that eating may be favorable “between 8 a.m. and 4 p.m., when FGF21 and adiponectin are produced and promote fatty acid oxidation, glycolysis, and inhibit fat accumulation.” Yet the same argument could be made for adiponectin promoting fatty acids or stored glucose release during a fast, helping to combat hunger.

The nuance for adiponectin’s role in benefiting either the fasted or fed state, may involve adiponectin’s transition in its role from catabolic (conducive to a fasted state) to anabolic (more appropriate for a fed state). This switch is mediated by the appearance of a third-party hormone: insulin. According to the study, natural insulin secretion occurs from 2-6 p.m., with a peak from 4-5 p.m. This would indicate that 2-6 p.m. might be a prime time for eating, due to insulin’s release. 

Additionally, 6 p.m. is also when the hunger hormone ghrelin peaks. 6 p.m. would therefore seem like a perfect time to eat, since hunger and fat storage hormones specifically involved in eating, are in full reign. A 2019 early vs late time-restricted feeding study (discussed in detail later), also found ghrelin was higher at 12 p.m. than 8 a.m., with circadian variation of hunger peaking later in the day. The researchers concluded that “prescription of TRF later in the day may have greater effects on reducing appetite and may aid compliance.” 

In fact, the 2015 Effect of extended morning fasting upon ad libitum lunch intake and associated metabolic and hormonal responses in obese adults looked at participants who ate either breakfast and lunch, or just lunch. Those who skipped breakfast and ate just lunch, unsurprisingly had lower levels of the satiety hormone leptin, yet, more surprisingly, had lower levels of the hunger hormone ghrelin. In other words, skipping breakfast reduced hunger. Furthermore, the breakfast skippers did not eat more at lunch than those who had breakfast, leading the researchers to conclude that “extended morning fasting does not cause compensatory intake during an ad libitum lunch nor does it increase appetite during the afternoon.”

 The 2021 Nutrients study, however, ironically, concludes that “the consumption of food should not occur during the insulin peak because it induces fat storage.” This also conflicts with what the study says later, that we should not eat when insulin is low during the night: “During the resting phase, insulin levels are reduced to the offset and beta-cell responsivity to glucose is lower. If glucose consumption occurs during the evening, the body will not be able to process it properly, leading to lower insulin sensitivity.” So according to the study, we should neither eat when insulin is high (because it promotes fat storage) nor when it is low (because then we won’t properly process food.) As such, it would seem that perhaps the researchers interpret insulin in whatever way most conveniently supports an earlier-eating schedule. 

 To me, it makes the most sense to eat when the hormones which make us hungry and tell us to store fuel, are naturally high. These are ghrelin and insulin, which both peak at 6 p.m. Ideally, we would also have a hormone present which would make us feel full. This would be leptin. Well guess what! According to the study, leptin begins rising at 4 p.m. and peaks at 7 p.m., before declining until 2 a.m. Leptin also “removes food intake, increases lipolysis, and inhibits fat accumulation”: all things we would want when eating! Ironically, the researchers interpret this differently, concluding that eating “should [not] occur at night when leptin is produced, since it normally induces satiety.” I honestly don’t follow this logic at all. Anyone? 

THE ROLE OF DARKNESS

To me, the data seems to clearly indicate that we are ripe for eating around 4-7 p.m. But what about after that? Should we eat into the evening? 

Intuitively, it doesn’t seem ideal to be actively digesting while sleeping, and studies consistently find decreased glucose tolerance in the evening. As noted in the previously discussed 2021 Nutrients study,“Glucose tolerance, for an identical meal, is higher in the morning (8 a.m.) than in the evening (8 p.m.), and similar rhythms have been observed in rodent models.” That said, an overwhelming number of these studies analyze participants eating throughout the day. It’s therefore hard to ascertain if the decreased glucose tolerance is due to an inherent temporal hormonal rhythm, or rather due to decreased glucose tolerance from extended eating all day. (One is typically most insulin sensitive when breaking a fast, which, in many of these studies, would be occurring for those eating breakfast, not dinner.)

 Diving even deeper, the pancreas features melatonin receptors, and melatonin inversely correlates to insulin. This indicates that darkness should be a time of high melatonin and low insulin, which does not seem appropriate for eating, as it could more likely encourage glucose intolerance. Since it is darkness, rather than timing, which most potently affects melatonin release (and consequently reduces insulin), I’d hypothesize that darkness, rather than evening per se, may be a primary factor in determining when we are best suited to not eat. This would support eating until the early evening to be appropriate, but not when the night begins to actually fall. 

THE ROLE OF CIRCULATING FUEL 

As a quick tangent worth exploring, fasted insulin and blood sugar levels may not even be the driving factor for insulin sensitivity, as questioned by the 1999 Diurnal variations in peripheral insulin resistance and plasma non-esterified fatty acid concentrations: a possible link? In the study, the researchers looked at the levels of non-esterified fatty acids (NEFAs) and insulin responses in 9 individuals, to a meal eaten at either 8:30 a.m. or 8:30 p.m., after an 11-hour fast. The researchers found that while fasted blood sugar and insulin levels were similar before both meals, the morning eaters experienced greater insulin sensitivity and faster reductions in glucose after the morning meal. 

The difference between the two windows seemed to be the level of circulating NEFAs. These were elevated prior to the evening meal, yet also dropped faster after the evening meal than after the morning meal. The researchers hypothesized that in the evening, tissues are more sensitive to taking in fats than glucose, and it is these circulating NEFAs which serve as the cause (rather than effect) of nighttime insulin sensitivity issues. (Of note, the night eaters in this study still ate  breakfast that morning, so I wonder if the effects might have been different, had they completely fasted all day.)

THE BREAKFAST BIAS

I realize I diverge significantly from a lot of these researchers’ conclusions surrounding timing of eating, such as in the 2021 Nutrients study: “Several hormone levels peak during the activity phase, suggesting early daytime is more optimal for food intake than evening. Thereby, the optimal time for food intake seems to be during the morning and the early afternoon.” As such, I would like to point out some of the inherent biases evident in this study, which often color arguments for earlier vs later eating in general. 

To start, the researchers argue against late-night eating with correlational (not causational) evidence, which is unrelated to timing. For example, the researchers proclaim that late-night eating is more associated with “processed and ultra-processed foods enriched in fats, salt, and sugar, [which] are positively associated with being overweight and obese,” and that “the consumption of these types of food associated with late-night dinner could be an aggravating risk factor of obesity, CVD, and diabetes.” This arguably bears no place in an analysis of the timing of meals, since these factors speak to composition only. (And umm… hello breakfast cereals?)

The researchers also note that “people with late dinner habits are more susceptible to consume larger portion sizes, second rounds, and energy-rich foods; these people also present a high fat mass, insulin resistance, and cardiovascular risks.” Again, this is the what and how much of the eating, not the when of the eating. One could just as easily say that breakfast foods encourage this behavior.

Connecting late-night eaters to typically higher weights, insulin resistance, and heart issues, while true, is correlational, as is the opposite common finding: that breakfast eaters are leaner, with less heart disease. But is this from the timing of the eating itself, or due to what is known as the “healthy user bias”? That is, we’ve been told for years that eating breakfast is healthy, so those who eat breakfast are often the type who naturally engage in other healthy lifestyle practices.

Perhaps most importantly, can we realistically draw any conclusions from late-night eaters correlating to health issues, when the majority of these late-night eaters were likely also eating throughout the day? Simply skewing the majority of the calorie intake to earlier vs later in the day, may have drastically different implications than only eating early or only eating late. This is a huge hurdle in evaluating the studies, because the former (those who eat throughout the day, but with the majority at night) may seem searingly relevant in its implications about meal timing, when in reality, it may bear little if any relevance. It may be that fasting throughout the day, and then eating only in the evening, reduces (if not eradicates) all the issues of eating later when also eating earlier. Unfortunately, it’s hard to know, as there are very few studies directly comparing an early vs. late-night time-restricted feeding window. Which brings us to…

EARLY VS. LATE EATING STUDIES

So, what have studies looking at early vs. late-night eating windows actually found? 

Well, there haven’t been many of them. 

 The 2019 Time-Restricted Feeding Improves Glucose Tolerance in Men at Risk for Type 2 Diabetes: A Randomized Crossover Trial published in Obesity, looked at 15 obese men who ate in a 9-hour time-restricted feeding window that was either early (TRFe) between 8 a.m. to 5p.m., or a delayed time-restricted feeding window (TRFd) that was later, between 12 p.m. to 9 p.m. The men first wore a continuous glucose monitor (CGM) for 7 days while following their normal diet; then implemented one of the TRF windows; then followed their normal diet for 2 weeks; then implemented the other TRF window. Their insulin, glucose, nonesterified fatty acids, triglycerides, and gastrointestinal hormone incremental areas under the curve (AUC), were tested right after their first meal breaking their fast, either at 8 a.m. or 12 p.m. 

The researchers found that TRF improved glucose tolerance, regardless if it were early or delayed. In fact, by day 7, the insulin and glucose response 180 minutes after the first meal at either 8 a.m. or 12 p.m. – for both insulin and glucose – was almost identical. The study notes that the AUC overall was better for the early feeding window (a 36% decrease vs 21% decrease in AUC), but looking at the charts, the trends are eerily similar by day 7, begging the question: would the AUC have normalized to match, had the experiment continued?  The insulin response for the delayed window was actually ever so slightly better 180 minutes after the meal at day seven, for the TRFd meal.  Looking at the graphs, participants also seemed to react differently with the TRFe vs. TRFd, with some participants experiencing better changes from the TRFd as well. This would indicate that perhaps a factor of individuality is important?  

Regardless, TRF did not significantly affect fasting insulin (although it was trending that way for insulin AUC), nonesterified fatty acids, or gastrointestinal hormones. Both fasting windows lead to weight loss, with no difference between them. (Although also of note, the control group also lost weight.) Interestingly, the early eaters may have naturally eaten in a longer window, since the averages were 8:22 – 4:37 (8 hours 15 minutes) for TRFe and 12:15 – 7:56 (7 hours 41 minutes) for TRFd, which would speak in favor of the earlier eating window having a more powerful weight-gain mitigating effect, if they were indeed eating for a longer amount of time, yet lost the same amount of weight.

The study concluded that “while only TRFe lowered mean fasting glucose, TRF improved glycemic responses to a test meal in men at risk for type 2 diabetes regardless of the clock time that TRF was initiated… This study suggests that there may be some flexibility in the clock time TRF is initiated… Overall, the simplicity of TRF and the efficacy in improving glycemic outcomes indicate that large-scale, long-term randomized controlled trials are warranted.

OTHER ENLIGHTENING STUDIES

To date, I can find no other studies directly comparing an early to late-night eating window in an intermittent fasting pattern, but we can still analyze the implications of other research. 

While the 2007 Impact of reduced meal frequency without caloric restriction on glucose regulation in healthy, normal-weight middle-aged men and women did not directly compare late-night to early night eating, it did compare a late eating one meal a day (OMAD) window (4-8 p.m.) to a more traditional 3 meals per day pattern, each for 8 weeks. The researchers found that the late-night window resulted in elevated blood sugar levels, delayed insulin response, and an impaired glucose tolerance test the next morning, but did not affect leptin and ghrelin.

Even before reading the researcher’s thoughts on this, I didn’t find it surprising that those who ate all of their food in a late window, had higher morning blood glucose compared to those who had eaten throughout the day (and thus likely a lighter dinner the actual evening before). The researchers drew this same conclusion, noting that “the latter difference in fasting glucose levels could be explained, in part, by continuing absorption of the greater amount of food consumed in the evening in the subjects on the 1 meal/d diet.” 

I’m also not surprised by the reduced blood glucose response to the glucose tolerance test, since those who followed the later evening window, likely were conditioned to process glucose later. And while the later eaters seemed more insulin resistant in the morning, other markers of impaired glucose tolerance – like fasting insulin, leptin, and glucagon – were not affected, nor were levels of ghrelin – the hunger hormone. Furthermore, researchers noted that “the 1 meal/d diet on glucose tolerance was rapidly reversed upon return to the 3 meal/d diet, indicating that the diet had no long-lasting effect on glucose metabolism” and “the impaired glucose tolerance was reversible and was not associated with alterations in the levels of adipokines or BDNF.” This indicates to me that the higher blood sugar levels and tolerance in the morning were likely a transient change adjusting to eating later, rather than lasting insulin resistance.

Despite consuming the same amount of calories, only the OMAD group lost weight. They also experienced significant increases in levels of total, LDL, and HDL cholesterol (which is often seen transiently with weight loss). Perhaps most significantly, this group was “forced” to eat more than they wanted, and “would have eaten less than those on 3 meals/day if we had not asked them to consume the same amount of food that they normally eat on a 3 meal/d schedule.” In other words, practicing a late-night eating window in a “real world” situation, would likely lead to a further natural reduction in calories, and subsequent weight loss. This naturally fulfills the researchers’ ultimate conclusion, that “the available data therefore suggest that meal skipping or intermittent CR diets can result in health benefits including improved glucose regulation, but only if there is an overall reduction in energy intake.” 

 In a similar setup, the 2007 A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults published in the American Journal of Clinical Nutrition, looked at 15 normal weight individuals who consumed either 3 meals per day for 8 weeks, or 1 meal a day from 5 p.m. – 9 p.m., with a washout period of 11 weeks, before trying the alternate version. The participants ate the same controlled amount of food for each, at a calorie intake to maintain their body weight.

The OMAD group experienced reduced fat mass specifically, while maintaining muscle. The group eating throughout the day did not. The OMAD group experienced increased hunger, desire to eat, and the perceived amount of food they thought they could eat, as well as less feelings of fullness. These effects intensified the longer they did the OMAD.  However, I find these observations a bit misleading in their implications, since they were taken before eating, and most of the participants reported “extreme fullness after the meal and had difficulty finishing their food in the allotted time.”  

While the participants consumed the same amount of macronutrients, fatty acids, cholesterol, and fiber between the 2 controlled diets, the researchers specifically chose energy-rich foods for the OMAD situation, to reduce the food volume. Perhaps if this initiative were not taken, there might have been even more weight loss or beneficial effects from natural calorie restriction. Ironically, the researcher concluded that “the present findings suggest that, without a reduction in calorie intake, a reduced-meal- frequency diet does not afford major health benefits in humans,” and that a “long-term reduced-meal- frequency diet that also includes a 20 –30% reduction in calorie intake would more closely resemble the intermittent fasting regimen that is widely used in rodent studies [that show benefits].” The irony here, is that the participants would have seemingly naturally restricted their calories, had they been in a free living situation.  

The OMAD approach also lowered BUN and slightly increased liver enzymes and albumin. Total LDL and HDL also increased compared to 3 meals a day, although, as previously noted, this often accompanies weight loss. That said, all remained in normal reference ranges. The researchers also found no difference between heart rate and body temperature. While the 3 meals a day pattern significantly lowered blood pressure by about 6%, the researchers noted this may be due to circadian rhythms, since blood pressure was taken in the late afternoon for the OMAD participants, and in the early morning for those eating 3 meals a day.

The timing of taking the blood, however, might also have affected the results. Blood was collected after a 12-hour fast (before breakfast) for the 3 meals/d, but after an 18-hour fast in the late afternoon before the OMAD group. The OMAD group also experienced a significant decrease in concentrations of cortisol, but this may have been due to the natural infradian rhythm of cortisol. 

In sum, the participants in the OMAD group were hungrier before their meals, but they lost more weight, maintained muscle mass, felt full, and had to be forced to finish their food. I wonder what would have happened, had they not been forced to finish their food, and also hadn’t purposely been fed high calorie, low volume food. Ultimately, the researchers concluded that “altered meal frequency is feasible in healthy, normal-weight, middle-aged men and women. Consumption of 1 meal/d resulted in weight loss and a decrease in fat mass with little modification in calorie consumption. It remains unclear whether altered meal frequency would lead to changes in weight and body composition in obese subjects.” 

THE TIMING OF MORNING GLUCOSE TOLERANCE 

The 2007 Impact of Reduced Meal Frequency Without Caloric Restriction on Glucose Regulation in Healthy, Normal Weight Middle-Aged Men and Women looked at the effects of all day eating vs. eating in an evening window from 5 to 9 p.m., for its effects on morning glucose tolerance. For the setup, the participants underwent 8 weeks of “normal” eating, as well as 8 weeks of the 4-hour pattern, with a washout period of 11 weeks in between.

The researchers found morning blood sugars were higher after the night eating window, with reduced glucose tolerance with a glucose tolerance test. (They were given a bolus 75 g of glucose in a 300 ml solution, to see how well they cleared it.) Interestingly, fasting insulin was not different between the groups, and despite having a greater blood glucose at baseline, there was no significant difference in insulin response to the morning oral glucose tolerance test.   

I don’t find these results the least bit surprising, since the late-night participants were coming off a much greater, and more recent calorie intake, relative to the testing. This was my initial thought when reading the setup, and then indeed, the researchers concluded that the “difference in fasting glucose levels could be explained, in part, by continuing absorption of the greater amount of food consumed in the evening in the subjects on the 1 meal/d diet…when on the 1 meal/d diet the subjects had consumed a much greater amount of food in proximity to the OGTT compared to subjects on 3 meals/d, which could have influenced morning insulin sensitivity.”

The researchers also noted the participants were forced to overeat in the 4-hour window situation: “When on 1 meal/d the subjects would have eaten less than those on 3 meals/day if we had not asked them to consume the same amount of food that they normally eat on a 3 meal/d schedule.” Like a previously discussed study, I do not believe the implications of this can be overstated.  

The researchers also note that glucose tolerance tends to be best in the morning, and it was not surprising that the 5 – 9 p.m. group responded more poorly, especially since they were not adapted to the morning eating, like the breakfast eating group.  Either way, the glucose intolerance was seemingly transient, and rapidly reversed when the participants returned to a pattern of eating throughout the day.

As for other markers, there was no significant difference in fasting ghrelin, glucagon, leptin, adiponectin, insulin resistance, or BDNF.

Ultimately, the researchers concluded that “our findings show that consumption of one unusually large meal per day worsens morning glucose tolerance compared to an isocaloric diet spread across three meals.”  All that said, if one is consistently implementing an OMAD approach at night, they are not eating in the morning anyways, so I’m not sure what are the actual implications of these findings, when evaluating the appropriateness of early vs. late eating.

   

TIMING AND RESISTANCE TRAINING

The 2017 Time-restricted feeding in young men performing resistance training: A randomized controlled trial looked at participants who ate either in a normal eating window, or in a 4-hour evening window, coupled with resistance training three times per week alternating lower and upper body workouts. The participants implemented the 4-hour eating window on their 4 non-workout days, and self-selected times between 4 p.m. – midnight, meaning they were all later evening eating windows. 

The researchers found that the participants naturally consumed an average of 667 less calories on their fasting days, with no significant changes in body composition or weight from the deficit in the fasted group as a whole. But looking at the overall results paints a misleading picture: while the calorie deficit in the fasted group did not hinder their muscle strength (both groups gained moderate to large upper and lower body strength from the workouts), they also did not gain as much muscle as the normal eating group: an average loss of .4 lbs for the fasted group, versus a gain of around 5 lbs for the fed group.

Looking even deeper at the individual data reveals a heterogenous picture of unique metabolic states, as well as the role of protein consumption. Individually, some of the fasters lost up to 5.5% of their overall weight, and 22% of fat specifically. Half of the fasted subjects also gained significant muscle mass, while the other half lost some. And while the fasted group did not gain as much size as the non-fasted group, they actually saw better improvements in upper and lower body endurance, as well as lower body strength. 

Out of both the fasted and non-fasted individuals, those who started off at a leaner composition tended to increase muscle, while those who started off fatter, tended to lose muscle, which may indicate something about whether their baseline metabolic state naturally favored preserving fat or muscle. 

The researchers also theorized any loss of muscle mass or failure to gain muscle in the fasted group may have been due to the group eating less protein, noting that studies have shown that adequate protein in calorie-restricted diets can promote muscle mass retention. Perhaps most importantly, when the relationship between the dietary changes were taken into account, a different picture materialized. Those who consumed more calories, carbs, and protein on their fasted days, tended to gain more lower body strength. Lastly, I also wonder if the potential irregular eating patterns for the meals had any effect, as the participants could eat in “any four-hour window between 4 p.m. and midnight.”

The researcher concluded that, “TRF does not appear to be detrimental to muscular improvements in young males beginning a RT progra.m.me, and the magnitude of improvements in muscular strength and endurance was equal to or greater than the improvements of those following their normal diet. While it is possible that TRF limits the ability to gain lean tissue during an RT progra.m.me, additional research utilizing matched protein intake at optimal levels for muscular hypertrophy is necessary.”

On the same topic of resistance training, the randomized, placebo-controlled 2019 Time-restricted feeding plus resistance training in active females: a randomized trial looked at continuous eating in active females, compared a normal control diet to time-restricted eating from 12 - 8 p.m., either with or without additional β-hydroxy β-methylbutyrate (HMB) supplementation during their resistance training. While the focus was on the HMB supplementation, the study nevertheless revealed the differences between all day eating, to the 8-hour window. The researchers found that, despite the same calorie and protein intakes, only the fasted patients lost fat. Both groups improved muscle performance, indicating a fasting approach was still significant for muscle improvement.  While this does not look specifically at a late window, it does seem to paint a favorable picture for afternoon to evening eating.  

THE ROLE OF SELECTION AND SOCIAL CONTEXT

An important factor to consider in all of this research, is the role of self-selection. In many studies, patients are delegated to a certain window, or mandated to consume all of their calories, regardless of satiety. For the former, the patients might have been more compliant if they had chosen a time window naturally of their liking. For the latter, a few studies noted that patients were made to consume more than they naturally would have. I’d hypothesize that if people naturally choose a time-restricted window they like, and only eat to satiety within it, then the potential benefits of time-restricted eating would be greater, even with later evening windows. 

As noted in the Cell Metabolism 2020 Ten-Hour Time-Restricted Eating Reduces Weight, Blood Pressure, and Atherogenic Lipids in Patients with Metabolic Syndrome, it “is also important to note that in all TRE studies in which negative effects were reported, the timing of the TRE was pre-determined for the participant. Taking an individual’s schedule and personal preference into consideration and letting the participants choose their own TRE interval are likely important factors for adherence, efficacy, and reducing adverse effects.”

The role of social factors and personal preference cannot be overstated. A major reason a later time window may work better for many people, may be how it aligns with social events. As noted in the Cell Metabolism study, “Although not considered a medically relevant adverse effect, a separate study that delayed breakfast and advanced dinner by 1.5 h each (resulting in an ∼8.5 h eating interval) reported that TRE affected opportunities for people to engage in evening social eating and drinking activities.”

The feasibility of adherence, taking into account personal preferences and social factors, is likely of key importance when experiencing lasting benefits from time-restricted eating. 

CONCLUSION

I’ve got to admit, I wasn’t sure what I’d find when I decided to tackle the scientific literature on early vs. late eating. Given the typical early-eating-is-best-late-eating-is-awful zeitgeist, it wasn’t looking too promising for my admittedly very late evening window. That said, I found the studies on the matter to be often conflicting, contradictory, or bearing an evident inherent bias for early eating, when you look closely enough at the data.

While we can waltz around in theories of hormones, and the “ideal window” in a perfect world of stubbornly clinging to said protocol, the practical implications of engaging in any given window, may make a measurable difference. After all, time-restricted eating seems to realistically provide benefits, regardless of the exact timing, even if that timing isn’t as “good” as it could be. I believe it’s therefore best when humans select a window which works for them personally, and which they can stick to. 

In other words, perhaps the best window, is the window you keep. Don’t let perfect be the enemy of good. If you enjoy fasting every day and eating at night, the literature – along with myriad anecdotal evidence - seems to indicate it will likely be very profitable for one’s health, just maybe not the breakfast cereal industry. 

RESOURCES

Early versus late time-restricted feeding in adults at increased risk of developing type 2 diabetes: Is there an optimal time to eat for metabolic health? 

 Meal timing regulates the human circadian system

 An effectiveness study of early or late time-restricted feeding on body composition – pilot study 

Beneficial effects of early time-restricted feeding on metabolic diseases: importance of aligning food habits with the circadian clock 

Adiponectin and human eating behaviour: a Mendelian randomization study 

Diurnal variations in peripheral insulin resistance and plasma non-esterified fatty acid concentrations: a possible link? 

A controlled trial of reduced meal frequency with-out caloric restriction in healthy, normal-weight, middle-aged adults. A.m. J Clin Nutr  

Early improvement of left ventricular function during caloric restriction in obesity 

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

Time-restricted feeding in young men performing resistance training: a randomized controlled trial 

Beneficial effects of early time-restricted feeding on metabolic diseases: importance of aligning food habits with the circadian clock  

Effects of cortisol on carbohydrate, lipid, and protein metabolism: studies of acute cortisol withdrawal in adrenocortical failure 

Effect of extended morning fasting upon ad libitum lunch intake and associated metabolic and hormonal responses in obese adults 

Time-restricted feeding improves glucose tolerance in men at risk for type 2 diabetes: a randomized crossover trial 

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

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

Ten-hour time-restricted eating reduces weight, blood pressure, and atherogenic lipids in patients with metabolic syndrome 

 

 

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