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The myth of the late meal

Der Mythos des späten Essens
  • If eating late at night impairs fat loss, why do people who eat more in the evening lose more fat than people who don't?
  • If carbs make you fat after 6pm, how is it that people who eat more carbs after 6pm lose more fat than people who eat their carbs earlier in the day?
  • If we should eat breakfast like a king, lunch like a prince and dinner like a beggar, why does skipping breakfast combined with late night binge eating lead to fat loss and improved blood lipid levels?
  • If eating late is bad for you, why does almost every controlled scientific study show that eating later in the day is better than eating earlier in the day? And if the above statements are true, why do people still believe that eating late is bad for you...?

The myth of eating late

There is a common belief among many people that it is better to eat more earlier in the day and less later in the day. Eating later in the day is said to impair fat loss and/or promote unwanted weight gain. This myth can best be summarized by the saying that you should eat like a king in the morning, like a prince at lunchtime and like a beggar in the evening.

You'll often find people clinging to the myth that carbohydrates will somehow suddenly make you fatter after 6pm - which is, of course, complete nonsense.

The facts on this are more interesting than what I have already said in previous articles on this topic. Controlled studies have repeatedly shown that a dietary pattern of eating later in the day is superior for fat loss and body composition.

In this article, I will look at some studies that look at the timing of calorie intake. I'll pay a little more attention to the last study, titled "Greater Weight Loss and Hormonal Changes After 6 Months Diet With Carbohydrates Eaten Mostly at Dinner," because it's the one that got me looking at this topic again in the first place.

A pressing question first: why is the myth about the negative effects of eating late at night still so widespread when there are so many studies showing the exact opposite?

Late night eating in nutritional epidemiology

In the comments on my site, a reader asked the following question:

"Is it okay to eat dinner 1 to 2 hours before bedtime? Every damn mammal goes to sleep after eating massive amounts of food - e.g. lions, dogs, bears, but at some point nutritionists came to the conclusion that we have somehow evolved. It would therefore be nice if someone could produce scientific evidence to show that we shouldn't eat before bedtime. I really don't understand why this should be the case, do you have an explanation for me?" Yes, how did nutrition experts come to the conclusion that eating before bedtime is bad for you?

The late night eating myth is mainly another consequence of the confusion between correlation and causation in the field of nutritional epidemiology. There are numerous observational studies that have observed a positive correlation between calories consumed in the evening and higher BMI in the general population. This correlation can be attributed to the fact that the average person who likes to eat more in the evening also consumes more calories overall. One study used food logs to find that late-night eaters consumed an average of 248 kcal more than members of the other group.

Similar relationships can usually be found in other observational studies on meal patterns. People who skip breakfast, skip other meals and eat late at night are on average fatter and worse off than people who eat breakfast, eat regular meals and eat less in the evening. However, this has nothing to do with meal timing per se, but more with the lifestyle that goes hand in hand with "dysregulated" eating habits.

A meal pattern that skips breakfast or breakfast and lunch has been associated with an accumulation of less healthy lifestyle factors and poorer food choices, leading to an overall poorer diet. ("Meal pattern, food choice, nutrient intake and lifestyle factors in The Göteborg Adolescence Study", https://www.ncbi.nlm.nih.gov/pubmed/14647222)

Late night eating was correlated not only with higher calorie intake, but also with less sleep time and more sedentary activities such as watching TV and spending time in front of the computer, which are other confounding factors that can promote weight gain.

Shift work and the internal clock

The purported risks of late-night eating may also be the result of the scientific literature on shift workers and metabolic health ("Shift work and the risk of metabolic syndrome: a nested case-control study.", https://www.ncbi.nlm.nih.gov/pubmed/21618947). Shift workers are predisposed to a variety of health problems, obesity, poor mental health, cardiovascular disease, stomach ulcers and gastrointestinal problems (probably the result of chronic stress). The negative effects of shift work on health are mainly the result of a compromised diet, sleep deprivation and stress - the factors tend to go hand in hand. However, it is possible that eating in a state of disrupted day-night rhythm and an irregular meal pattern is an independent factor in predisposing shift workers to poor health.

People can adapt to a variety of different eating patterns depending on their habitual meal pattern. This adaptation takes place at a cellular level and is regulated by ghrelin - a hormone that is released in greater quantities during habitual mealtimes and prepares your metabolism to best cope with the upcoming load of food. Similarly, the day-night rhythm - when you wake up and when you go to sleep - is regulated by daylight and the habitual sleep/wake cycle and also adjusts your metabolism accordingly.

Simply put, your body expects a certain routine every day depending on your habitual eating patterns and sleep/wake rhythm and adjusts its hormonal profile and metabolism. If this pattern is arbitrary and constantly shifted forward and backward, never allowing your body to adjust, as is the case with many shift workers, then it is very possible that this is an independent factor that makes people more susceptible to disease and health problems. The hormonal profile of shift workers, moreover, tends to be less favorable than that of people with a regular circadian rhythm.

It should be noted that permanent shift workers, i.e. those who always work at night or work several nights in a row, are better off than other shift workers, which can be partly explained by a change in the day-night rhythm. It seems that an "unpredictable" schedule, i.e. rotating day and night shifts, is the main culprit, as the day-night rhythm is constantly disrupted. Given the many confounding factors such as stress, sleep deprivation, caloric intake, etc. present in shift workers, it is difficult to isolate which factor is responsible for what - i.e. is food intake during the biological night worse than sleep deprivation, etc.

Nutritional epidemiology vs. controlled studies

We are not interested in the studies mentioned above. What we are interested in are controlled studies - not nutritional epidemiology and observation in the general population. If you use nutritional epidemiology to tell people how they should eat, then you get the typical food pyramid. If you use controlled studies to draw your conclusions, you get something that is more meat- and vegetable-heavy.

Controlled studies answer questions like "I'm on a 2000 kcal diet. How will my fat loss be affected if I eat most of those calories later in the day or if I eat more of those calories earlier in the day?" This is something we are interested in, so let's take a closer look.

Early eating vs. later eating regimens: controlled studies

In all of these studies, calories were controlled and fixed in all groups. The only variable that differed was the timing of the daily calorie intake. In the later meal pattern, 67 to 100% of calories were consumed between 18:00 and bedtime and this was compared to an earlier meal pattern with the opposite timing of calories. Let's start with the earliest study and work our way up to the most recent. I will briefly summarize the results, comment on the validity of the study, and interject whatever I find interesting about this study.

I want to note that I did not include any studies on Ramadan fasting. In only loosely controlled studies of Ramadan fasting, fat loss and improvements in health markers are usually observed. This is a paradoxical and interesting observation due to the fact that people eat in the middle of the night just before going to bed and usually eat even more sugar and baked goods than usual (and sometimes even more calories). However, in these studies, calorie intake is rarely actually controlled, i.e. participants did not have strict guidelines on what they should eat, which is the reason I did not use these studies in this review.

Study #1

Chronobiological aspects of weight loss in obesity: effects of different meal timing regimens. (https://www.ncbi.nlm.nih.gov/pubmed/3508745) (Chronobiological aspects of weight loss in obesity: effects of different meal timing regimens)

Results: This first-ever calorie-controlled study on meal timing, conducted in 1987, found that weight loss did not differ if subjects ate their daily calorie intake in the morning (10 am) or evening (6 pm).

Although it is interesting to note that fat oxidation was consistently higher in the group that ate in the evening, the duration of the study (15 days) was very short, making it difficult to draw meaningful conclusions from it. Apart from the differences in fat oxidation, there were no differences in cortisol levels, blood pressure or resting energy expenditure between the two groups.

Study #2

The role of breakfast in the treatment of obesity: a randomized clinical trial. (https://www.ncbi.nlm.nih.gov/pubmed/1550038) (The role of breakfast in the treatment of obesity: a randomized clinical trial).

Results: In this well-designed 12-week study, the subjects were people who habitually ate breakfast and people who did not normally eat breakfast. Interestingly, fat loss was greatest in people who normally ate breakfast but skipped breakfast during the study. This group ate lunch and dinner and consumed 2/3 of their daily calories at dinner (6:00 pm or later). The subjects who did not normally eat breakfast and who now ate breakfast achieved more positive results than those who continued to skip breakfast as usual. The implication of these seemingly paradoxical results could be related to impulse control - dysregulated eating habits such as not eating breakfast tend to go hand in hand with unrestrained or impulsive eating. Eating breakfast could therefore be beneficial for those with poor self-control, such as the former breakfast deniers in the study.

On the other hand, more desirable results could be achieved for the "controlled" eaters (habitual breakfast eaters) who now abstained from breakfast. This group would be more representative of us - i.e. people who are used to counting calories, following an organized diet and not just carelessly eating what is in front of us. Incidentally, there were no differences between the groups in terms of weight loss composition (75% fat / 25% lean body mass) or metabolic rate at rest. Interesting tidbit: The group that ate breakfast showed a slight increase in depression-induced eating, while subjects in the group that did not eat breakfast showed a slight reduction. In addition, subjects in the breakfast group viewed their diet as more restrictive than subjects in the group that did not eat breakfast.

Here is a quote from the study:

"...the larger meal size in the group that did not eat breakfast caused less disruption to meal schedules and social life than the smaller meal size in the group that ate breakfast."

Perhaps it was these beneficial effects on social life that also resulted in the non-breakfast group showing better continued adherence to the modified diet during the 6 months following the study (81% vs 60%).

Study #3

Weight loss is greater with consumption of large morning meals and fat-free mass is preserved with large evening meals in women on a controlled weight reduction regimen.

(https://www.ncbi.nlm.nih.gov/pubmed/9040548) (Weight loss is greater with consumption of large morning meals but fat-free mass is better preserved with large evening meals in women on a controlled weight reduction regimen). Results: In this study, subjects alternated between two 6-week phases of the same diet in which 70% of daily calories were consumed either in the morning or evening. Larger morning meals compared to larger evening meals resulted in greater weight loss, but this weight loss consisted of muscle mass. Overall, larger evening meals maintained existing muscle mass better and resulted in a greater reduction in body fat percentage.

The greater weight loss associated with the larger morning meal eating pattern was primarily due to a loss of lean body mass, which was on average about 1 kilogram higher in the larger morning meal group than in the larger evening meal group.

An interesting study with a few obvious limitations, mainly that the number of subjects was very small at 10 participants and that body composition was measured using electrical conductivity - a method that is chronically inaccurate.

This study also included training with weights three times a week, which was a serious confounding factor in this study. Considering that the group that ate the most calories later in the day ate a greater percentage of their calories after exercise, this study may also simply show the benefits of nutrient timing rather than larger meals in the evening per se.

Setup with larger food intake in the morning

  • Breakfast, 8:00-8:30am: 35% of daily calorie intake
  • Training with weights (circuit training), 9:00-9:30 a.m.
  • Lunch, 11:00-12:00: 35% of daily calorie intake
  • Dinner, 16:30-17:00: 15% of the daily calorie intake
  • Evening snack, 20:00-20:30: 15% of the daily calorie intake

Setup for larger food intake in the evening

  • Breakfast, 8-8:30 a.m.: 15% of daily calorie intake
  • Training with weights (circuit training), 9:00-9:30 a.m.
  • Lunch, 11:00-12:00: 15% of daily calorie intake
  • Dinner, 16:30-17:00: 35% of the daily calorie intake
  • Evening snack, 20:00-20:30: 35% of daily calorie intake

Finally, the scientists speculated on the muscle-sparing effects of the meal pattern with larger meals later in the day:

"Certain endocrine influences may have contributed to the differences in lean body mass changes between meal schedules. Growth hormone secretion reflects an endogenous rhythm that is partially related to the sleep cycle. At night, pulsatile growth hormone secretion increases after 1 to 2 hours of sleep, with maximal secretion occurring during stages 3 and 4 of the day.

Although the effects of prolonged changes in food intake or meal pattern on growth hormone release are not known, it is conceivable that a greater influx of dietary amino acids at evening meals, combined with the known protein anabolic effects of growth hormone, could promote lean muscle mass gain.

Study #4

Influence of meal time on salivary circadian cortisol rhythms and weight loss in obese women. (https://www.ncbi.nlm.nih.gov/pubmed/17483007) (Effects of meal timing on salivary circadian cortisol rhythms and weight loss in obese women).

Results: Using exactly the same setup as the previously mentioned Sensi & Capani (1987) study, it was found that dividing daily caloric intake into five meals eaten every other hour between 9:00 am and 8:00 pm, eating all calories in the morning (9:00 am to 11:00 am) or eating all calories in the evening (6:00 pm to 8:00 pm) did not differentially affect weight loss, metabolic rate, or cortisol levels. The limitation was again a very short duration of each phase (18 days).

Here's a quote for those concerned about cortisol and fasting: "At the end of the phases of the study, we did not observe any significant changes in the diurnal rhythm of cortisol secretion, regardless of the timing of food intake, even after 22 hours of fasting."

It might be worth noting that nitrogen loss, which is a crude marker of muscle loss, was not affected by the timing or frequency of meals - there was no difference between the 5 meal phase and the 22 hour fasting phases in the morning/evening meals.

Study #5

Greater Weight Loss and Hormonal Changes After 6 Months Diet With Carbohydrates Eaten Mostly at Dinner. (https://www.ncbi.nlm.nih.gov/pubmed/21475137) (Greater Weight Loss and Hormonal Changes After 6 Months Diet With Carbohydrates Eaten Primarily at Dinner)

In this most recent and well-designed 6-month study of calorie distribution throughout the day, subjects who ate most of their daily carbohydrates at dinner (8:00 pm or later) lost more fat, felt fuller during the diet, and experienced more desirable hormonal changes than subjects who ate their carbohydrates earlier in the day. Background: This study is based on the premise that the daily peak of leptin levels can be altered, as can be observed during Ramadan. Previous studies have described the typical diurnal pattern of leptin secretion, which falls during the day from 8:00 am to 4:00 pm, reaches its lowest point at 1:00 pm, rises from 4:00 pm and reaches its maximum at 1:00 am. Ironically, this important hormone, which is responsible for satiety, has its highest levels when we are asleep. It was hypothesized that consuming carbohydrates primarily in the evening could alter the typical diurnal pattern of leptin secretion as observed in Muslims during Ramadan.

Simply put, the aim of the study was to determine whether it is possible to shift leptin release to strategically achieve better satiety and dietary adherence in the morning and midday of the next day, rather than having the leptin peak during the night (as is the case with the standard diet). "...it was predicted that this diet would lead to higher relative leptin concentrations starting at 6:00 to 8:00 am and throughout the day. This could lead to increased satiety during the daytime hours and improve dietary adherence." At this point I should note that leptin shows a significant latency in response to carbohydrates - if you eat carbs before sleep, then you won't experience the peak of leptin release until you wake up in the morning (another bonus is that you'll sleep well with a few carbs before bedtime).

This study also wanted to examine the effects of the experimental diet on adiponectin:

"Adiponectin is thought to be the link between obesity, insulin resistance, and metabolic syndrome. Adiponectin plays a role in energy regulation and fat and carbohydrate metabolism, reduces serum glucose and lipid levels, improves insulin sensitivity and has anti-inflammatory effects. The pattern of daily adiponectin release has been described as low during the day in obese individuals (especially those with greater abdominal fat deposition)." Low adiponectin levels = bad. High adiponectin levels = good. When insulin levels are low, adiponectin levels are high, but adiponectin also follows a diurnal rhythm - low during the night, high during the day (in normal weight people).

"...it has also been hypothesized that the increasing adiponectin levels during the day

adiponectin concentrations during the day would improve insulin resistance, reduce symptoms of metabolic syndrome and lower levels of inflammatory markers." In overweight people, chronically high insulin levels cause chronically low adinopectin levels, which is a problem because it increases insulin resistance and inflammation. The authors of the study hypothesized that by eliminating carbohydrates earlier in the day, adinopectin levels would increase more than with a conventional diet and health markers would also improve.

Setup: Both groups received the same diet split between breakfast, lunch and dinner and three snacks (morning, noon, late evening):

  • 1300-1500 kcal
  • 45-50% carbohydrates
  • 30-35% fat
  • 20% protein

Group A received the carbohydrates evenly distributed over meals and snacks. Group B received the majority of their total daily carbohydrate intake (approx. 170 grams) at dinner. There were no details regarding the exact macronutrient distribution of each meal, but the printed version of this paper includes the full meal plans for both groups. I would estimate that Group B consumed approximately 100 to 120 grams of carbohydrate during dinner.

Results: Both groups lost weight and saw improvements in different health markers, but Group B lost more weight (-11 kg vs. -9 kg), body fat (-7% vs. -5%), felt fuller and improved their hormonal profile better than Group A. "Hunger levels were lower and there were greater improvements in fasting blood glucose levels, average daily insulin concentrations and homeostatic model assessment for insulin resistance (HOMAIR), T-cholesterol, LDL cholesterol, HDL cholesterol, C-reactive protein, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) levels compared to the control group." As predicted, the high-carbohydrate dinner was able to alter the levels of leptin and adiponectin in a way that promoted better satiety and a better hormonal profile.

"The experimental diet modified leptin and adiponectin concentrations compared to baseline and control diet levels. A simple dietary manipulation of carbohydrate distribution appears to have additional benefits in people suffering from obesity compared to a conventional weight loss diet." However, what I found most interesting - at least for those of us who want to maintain a low body fat percentage - was that the higher carbohydrate dinner increased average leptin levels compared to the standard diet. "Our experimental diet could manipulate daily leptin secretion and lead to higher relative concentrations throughout the day. We hypothesize that this modification of hormone release helped study participants achieve better satiety during the waking hours of the day, which improved diet adherence in the longer term and led to better anthropometric outcomes." This study was solid, but for some reason there was no mention of how body fat percentage was measured. In addition, calorie intake was not individualized and based on energy needs. However, since each subject had the same occupation (police officer), it is fair to assume that physical activities did not vary greatly on an individual basis. In addition, the sample size was quite large (78 subjects), making it unlikely that the results were biased by these factors.

Summary

Nutritional epidemiology usually finds associations between certain meal patterns and higher BMI/body fat percentage. However, the relationship can be attributed solely to lifestyle-related factors and dietary habits such as snacking while watching TV, generally poor food choices, etc. People who eat more in the evening simply consume more calories, which explains why they weigh more.

Calorie-controlled studies that look at the effects of varying the distribution of a fixed amount of calories throughout the day are few and far between - I've listed all of them above. These studies tell a completely different story than the studies found in the field of nutritional epidemiology. While short-term studies (15 to 18 days) find no statistically significant differences between meal regimens with earlier or later food intake, long-term studies (>12 weeks) show that dietary regimens with higher calorie intake later in the day produce superior results in terms of fat loss, body composition and/or diet adherence. This could be explained by more favorable post-meal nutrient partitioning due to hormonal modulation. I understand that these facts will be hard for some people to swallow considering all the negative things they've heard about late-night eating. But then again, we hear a lot of strange things in the health and fitness community. And rarely do these tales match reality - just think of all the myths about fasting, alcohol and meal frequency.

That's it for today. I hope you've enjoyed this article and are now reassured that there's nothing wrong with eating late and eating big meals before bedtime.

Source: https://leangains.com/is-late-night-eating-better-for-fat-loss-and-health/

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