Some experts say that, “if the total daily caloric intake is the same, it doesn't matter how many meals a day you eat," but I assure you that the number of times you eat definitely affects your weight gain (or loss).
Indeed, if total caloric intake alone were the direct cause of weight gain, then frequency might not matter much, but my theory, as I have explained many times, is different from that.

In this case, I think it doesn’t have much to do with how many meals you eat a day. Rather, it’s the caloric or carbohydrate intake that matters. People who normally keep their weight lower through dieting or who cut excess body fat through workouts can gain weight if their caloric intake is higher than necessary, regardless of the number of meals they eat.
　　

As for part (A), the frequency of eating has a lot to do with it. Since base weight itself goes up by inducing intestinal starvation, eating more frequently and in a more spread out manner is less likely to result in weight gain. When you feel a little hungry, other foods enter your stomach again, which means that undigested foods are more likely to remain in your gastrointestinal tract. 

Conversely, less frequency of eating and longer periods of time between meals can cause intestinal starvation, which can lead to an increase in base weight value.

Let me explain (A) when the base weight is increased.

Based on my idea, people tend to gain weight if they skip breakfast or lunch and eat only two meals a day. However, eating two meals a day does not necessarily make everyone overweight. 

Actually, how many meals you eat a day is a matter of "meal intervals," and is only one of the "three(+one) factors” conditions that induce intestinal starvation.

Three (+one) Factors to Accelerate “Intestinal Starvation”

The most important thing is, "what to eat." But in addition, a person's digestive ability and the way they eat (eating speed, number of times they chew, and hydration during meals, etc.) also have a great impact.

For instance, even if everyone eats exactly the same food, people who can digest them faster reach the state of intestinal starvation faster. Also, even if the number of meals is the same, the time of day at which you eat also makes a difference (late lunch, late dinner, etc.).

Let me explain this in greater detail with some examples.  

<A co-worker who gained weight with only one meal a day>

When I was working part-time in a restaurant in college, there was a co-worker who gained almost ten kilograms since he started working. 

He ate only the meal for employees there that was served at night and nothing else, which meant that he had one meal a day. In his high school days, it seemed like he could not gain weight even though he was eating three meals a day and more calories. 

<A friend of mine who gained ten kilos by eating four to five meals a day>

A friend of mine gained more than ten kilograms by eating four to five meals a day when he was studying for a college entrance exam after he failed the first try. He belonged to a judo club in high school, and was very thin, even though he ate a lot of calories. But please note that it is not that the five meals a day that makes you fat, but what you eat and how you eat that matter. 

Although I cannot make an assertion based on just the number of meals, I believe that increasing the frequency of your meals is one correct way to lose weight. According to a study by Professor Saeko Imai at Osaka University in 2014, there was a change in blood sugar levels in diabetic patients depending on what time of day they ate cookies. 

In some cases, observational studies that examine the "association between meal frequency and being overweight" may go wrong.

For example, suppose you survey obese or overweight people and asked them how many times a day they eat. Let's assume that most of them answered four to five times. But you cannot take the aggregate results and say, “eating four or five times a day makes you gain weight.” 

The reason for this is that the most important things are missing: what you eat, and how much you eat, etc. As I said earlier, if one hamburger or one cup of noodles counts as "one meal," it makes no sense.

Second, we never know if they gained weight because they ate many times, or they ended up eating as a result of being too hungry.

(1) Some experts say that, “if the total daily caloric intake is the same, it doesn't matter how many times you eat," but from my intestinal starvation theory, the number of meals definitely affects weight gain (or loss).

(2) The number of meals is a matter of "meal intervals" and is one of the "three(+one) factors," conditions that induce intestinal starvation. Although eating one or two meals a day tends to increase weight gain in the long run, the most important thing is "what you eat” and other factors also influence this.

(3) Increasing the number of meals may also help you lose weight. It is important to leave more undigested food in the intestines and to not feel hungry.

(4) Observational studies that only examine “the association between meal frequency and being overweight” are meaningless. The reverse causality may occur: some people are too hungry and as a result, eat four or five times a day.
   

In Japan, many people (especially women) tend to avoid eating dinner, a dessert or sweets late at night (after nine p.m.) because they do not want to gain weight.

But does that really make sense? Actually, some people say that they have started eating dinner late at night and gained more weight than before, but I believe that is a misconception.
     

While we sleep at night, our bodies are not resting. They are doing something very important for us. Although the mechanism may not be entirely understood, sleep is an important time for not only organizing and consolidating memories in the brain, but also for repairing and regenerating damaged tissues to prepare for the next day's activities. 

On the other hand, I sometimes hear that people did not gain weight when they were eating dinner around seven p.m., but gradually gained weight over time after working overtime and eating late at night.  But that is a separate issue from [1] above, and it can be explained by the fact of one’s base weight itself going up in my intestinal starvation theory. 

First of all, many people tend to skip breakfast if dinner is served late at night. This means, in most cases, they only have two meals a day, lunch and dinner.

In Japan, many experts confuse the two meanings of [1] and [2], and explain them as if the secretion volume of BMAL1(Brain and muscle Arnt-like protein-1 ) and weight gain are correlated.

For example, if they eat a meal at ten p.m., it will take four to six hours for it to be digested and absorbed, depending on the person and how foods are combined, etc . Fats/oils are particularly indigestible, so they may find that even in the morning after seven to eight hours, their food is still undigested and their stomach is upset.

If people eat breakfast, lunch, and dinner properly, I believe, for most of them, eating before bed does not cause much weight gain.

As I said earlier, if a person who normally moderates their caloric intake eats sweets or ramen late at night, they may gain a few kilograms, but it means their present weight goes back to their base weight and should stop at a certain weight. (This should be easily proven by research.)

Also, In Japan, it is said that there are many thin people who have weak stomachs or droopy stomachs (gastroptosis), and even if they eat dessert, sweets or a light meal before bedtime in addition to their three meals in order to gain weight, it is more likely that they will not gain weight. In fact, I suppose that they may even lose weight (at least to me, this is one hundred percent true).

(1) In relation to hormones secreted, protein and lipid synthesis may occur more during sleep, so in a sense, everyone should be more likely to gain weight with dinner than in the daytime. Especially those who usually eat fewer calories because of dieting will gain a few kilos if they eat more calories than necessary at night. But in this case it doesn't matter whether they eat at seven p.m. or ten p.m.

(2) In terms of my intestinal starvation theory, late-night eating habits can lead to an increase in weight. Those people tend to skip breakfast and eat two meals a day. If they eat a carbohydrate-rich, unbalanced meal for lunch and hold off until a late dinner, it can lead to inducing intestinal starvation and an increase in base weight over time.

(3) I believe it is unreasonable to correlate the secretion volume of BMAL1－a protein involved in the body's circadian rhythms－which is related to adipogenesis, with meal time, and that say that, “late night eating makes people gain weight.” This is because the time required for digestion and absorption is not taken into account.

(4) For some thin people who want to gain weight, eating a high-calorie meal or a sweet before bed in addition to their three meals a day would probably work in the direction of losing weight. Even while sleeping, energy is used more towards digestion and absorption, which may result in decreased cellular regeneration and the synthesis of protein and lipids.
       

In the previous article, I introduced the concepts of a "biological clock," and “chrono-nutrition,” but if you have not read them yet, please read the following article first.
This time, I am going to state my own thoughts on how eating breakfast affects weight management concretely by my intestinal starvation theory. 

[Related article]  Why "When to Eat?" Is Important in Weight Management
    

In Japan, it is often said that lean people who eat a lot but do not gain weight have a fast metabolism. On the other hand, those who tend to gain weight are often told that they have a slow metabolism. The word “metabolism” has been used like a magic word. 

The same idea goes for breakfast. Eating breakfast will raise body temperature and metabolism, and the extra calories from breakfast and lunch will be burned off, so it is thought that people won’t gain weight even if they eat a lot. Many researchers and experts use metabolism as a silver bullet or a cure-all to solve obesity, but I beg to differ. It has already been proven that people who are overweight have a faster basal metabolism.[1]
  

I think the concept of “chrono-nutrition” is very important in this day and age, but there are many aspects that cannot be explained by metabolism or hormones alone. I believe, as I have mentioned in previous articles, that it makes more sense to explain this with my intestinal starvation theory.
   

Breakfast is the start of the day, and when you eat breakfast, your resting gastrointestinal tract becomes active.

If you eat a variety of food at that breakfast, such as dairy products, fibrous vegetables, seaweed, legumes, and fish or meat products, you can prevent intestinal starvation because undigested food will remain in your intestines for around ten hours or so (this is because our intestines are seven to eight meters long). 

Also, if you eat well both at lunch and dinner, you are less likely to gain weight, since there is some undigested food remaining over a twenty-four-hour period in your gastrointestinal tract  (it means that your base weight does not go up).

On the other hand, breakfast can be fattening (in the sense that it increases one's base weight) even if one eats it. It is a so-called inverted triangle-type diet, in which breakfast and lunch are light (one might even skip lunch) and dinner makes up for the missing nutrients and calories.

If lunch is also a simple carbohydrate-based meal and lacks fiber and other nutrients, all the food in the intestines will be digested by dinner, which makes it easier to develop a state of intestinal starvation. 

In short, if breakfast is well-balanced from various food groups, you are less likely to gain weight, but if it is a simple and unbalanced one, there is good chance you will gain weight over the long haul. 

Some chrono-nutritionists say that “an unbalanced breakfast makes the body clock reset halfway, and your metabolism remains slow” but other research has shown that the combination of “glucose and protein”－food that raises insulin levels－is best for starting the body clock,[2] so in this case, I think the explanation "you gain weight easily since your metabolism doesn't start properly,” does not apply.
   

Skipping breakfast does not make everyone fat, but I think, if some conditions are met and overlapped, it makes you more likely to gain weight.

The biggest issue is simply a matter of "what to eat" at lunch and dinner and the interval between meals. Eating only two meals a day makes the meal intervals longer. If you finish dinner at nine p.m., you will not eat for almost fifteen hours until the next day, at noon.

Skipping breakfast makes you hungry, so in Japan, people tend to eat a carbohydrate (rice or noodles)-and-meat-focused meal. Some of them are satisfied with just being full, and their meal may lack fiber and other nutrients.

You can prevent intestinal starvation by doing the following: If you don't have time to eat in the morning, at least drink some milk, or eat a balanced lunch with a smaller amount of carbohydrates. And if you have to eat late dinner, eat something such as milk, chocolate or nuts, even around five p.m.

References：
[1] Dr. Jason Fung, The Obesity Code, 2016, Page 62.
[2] Akiko Kotani(古谷彰子), Chrono-Nutrition Reveals the Rules for Eating (時間栄養学が明らかにした食べ方の法則), 2014, Pages 97-98.
    

(1) Breakfast is the start of the day, and a well-balanced breakfast prevents intestinal starvation by allowing undigested food in the gastrointestinal tract to remain around ten hours. If you eat three balanced meals a day, some undigested food will stay in your stomach all day long, and your base weight will be less likely to go up. If a person who is originally slim or medium-sized continues such habits, they are likely to maintain the same body shape, but if a person is already overweight, eating breakfast does not necessarily mean that they will lose weight (since their base weight is already high).

(2) If breakfast is skipped and meals are eaten twice a day (lunch and dinner), the interval between meals will be longer, which can easily cause intestinal starvation, depending on what you eat. Eating a carbohydrate-rich meal at noon when you are starving is also bad for your health in terms of raising blood glucose to somewhat unhealthy levels.

(3) Even if you eat breakfast, if your breakfast and lunch are simple and unbalanced, you are more likely to induce intestinal starvation before dinner. This kind of eating habit may increase your weight in the long run, even if the amount of food eaten is small.

(4) The reason why "when you eat, what you eat, and how you eat" affects weight management is because it closely ties into the movement of the intestines. The influence of hormones, of course, cannot be ignored, but it feels odd to explain it simply by giving the excuse of, ”It’s your metabolism.”

In this article, I would like to introduce the basic concepts of a "biological clock" and "chrono-nutrition" in Japan and consider the importance of eating breakfast.  I will write about “late dinners” in another blog.

Long story short, I recognize the importance of "when to eat, what to eat, and how to eat," and I have no objection to the statement that eating a balanced breakfast is important not only for your health but also for prevention of weight gain.

However, I am uncomfortable with the use of "metabolism" as a catch-all term to explain whether you gain weight or not. Is “metabolism” such a panacea？ I believe it should be better explained using my intestinal starvation theory.

First of all, I would like to introduce the concept of chrono-nutrition from the book, “Clock Gene Diet" by Professor Yasuo Kagawa. Please note that this is only the content from the book and may differ from my own ideas.

"As of 2012, the number of diabetic patients in Japan is about eight-point-nine million (or twenty-two-point-one million including prediabetics). Diabetes started increasing in the 1970’s.

Then, you might think, “it is because Japan became rich and Japanese people started eating delicious food,” but the average daily energy intake dropped from twenty-two-hundred kcal (in 1970) to eighteen-hundred and fifty kcal (in 2010). 

"Recent research has unraveled this mysterious phenomenon. It was a discovery of a clock gene of humans in 1997. Not only humans, but also all animals and plants have a “circadian rhythm” in which one day is twenty-five hours.

When we wake up in the morning and the sunlight (blue wavelength) is transmitted to the “central clock gene” in our brain, the twenty-five-hour circadian rhythm is reset to twenty-four hours and the day starts.

"In Japan, the term “chrono-nutrition” was used for the first time in 2008 by the Japan Society of Nutrition and Food Science. The more people try to lose weight, the harder they try to decrease the amount they eat from morning until night, but the effect and influence differ significantly depending on the time of day when food is consumed.

From early morning until about four p.m., the body is less likely to store body fat, and after nine p.m., calories are more likely to be stored as body fat.

It is said that the following three are important: ①When to eat (the timing of the meal), ②What to eat (dietary balance), and ③How to eat (the order of eating, the number of meals, etc.)."[3]
  

On the other hand, if breakfast is skipped, the metabolic rate remains slow and the body is prone to weight gain. A calorie-dense meal comes in all at once at noon, and it cannot be converted into energy rapidly, making it easier to accumulate body fat."[4]
    

"Eating vegetables first, followed by main dishes such as meat/fish, and then carbohydrates last, prevents a rapid rise in blood glucose levels, making the same menu less fattening.

Eating two meals a day, for example, is prone to storing fat in the body over time. It is better to divide it into multiple portions and eat one small portion at a time, even though it is the same total amount of food.

If you have to eat dinner late at night (e.g. at nine p.m.), it is better to divide your meal and eat carbohydrates by six p.m. and the other side dishes at nine p.m."[5]
      

While the total daily caloric intake remains important, I think it is great progress that people came to understand that even with the same caloric intake, " when you eat, what you eat, and how you eat it" can affect obesity prevention and dieting. And I understand that the time of day we eat can make a difference in the production of hormones.

If eating breakfast boosts the metabolism and consumes all the calories taken in that morning and at noon, then overweight people should be able to lose weight if they eat breakfast. 

According to an intervention study conducted in the U.S. in 2014, overweight or obese subjects were randomly divided into "eat breakfast" and "skip breakfast" groups to see if there was an effect on weight loss, but it seemed that no visible impact was found.[6]

As I mentioned at the beginning, my intestinal starvation theory should be more fitting to explain the benefit of eating breakfast. In the following article, I will explain, “why eating a balanced breakfast leads to the prevention of weight gain” based on my theory.

[Related article]  The Reason Why a Well-Balanced Breakfast Helps Prevent Weight Gain

References： 
[1] Prof. Yasuo Kagawa(香川靖雄) , Clock Gene Diet (時計遺伝子ダイエット), 2012, Pages 15-6.
[2]Pages 17-24.  [3]Pages 28-30.
[4]Pages 64-67.  [5]Pages 54-57.
[6] The effectiveness of breakfast recommendations on weight loss: a randomized controlled trial,2014