Can Thermodynamics Explain Why We Gain Weight?


  1. What does the first law of thermodynamics tell us?
  2. The human body is a mass of chemical reactions 
  3. Calories eaten is not the same as calories the body takes in. My thoughts
<The bottom line>

First, please read the following article. 
The Calorie Principle and Weight Gain; The Causality Has Been Obscure

According to Gary Taubes, it was first claimed in the early 1900’s by Carl von Noorden (a German diabetes specialist) that we gain weight because we take in more calories than we expend. This argument has continued to the present day, and we are told that taking in too many calories and lack of exercise are the causes of weight gain. 

This time, I would like to share the “law of thermodynamics,” which was said to be the basis for that theory. Mainly quoted from the book, it is so interesting that I think it is worth reading.

1. What does the first law of thermodynamics tell us?

"There are three laws of thermodynamics, but the one that the experts believe is determining why we get fat is the first one.

This is also known as the law of energy conservation: all it says is that energy is neither created nor destroyed but can only change from one form to another.

Blow up a stick of dynamite, for instance, and the potential energy contained in the chemical bonds of the nitroglycerin is transformed into heat and the kinetic energy of the explosion. 

Because all massour fat tissue, our muscles, our bones, our organs, a planet or star, Oprah Winfreyis composed of energy, another way to say this is that we can't make something out of nothing or nothing out of something.

This is so simple that the problem with how the experts interpret the law begins to become obvious.

All the first law says is that if something gets more or less massive, then more energy or less energy has to enter it than leave it.

It says nothing about why this happens. It says nothing about cause and effect. It doesn't tell us why anything happens; it only tells us what has to happen if that thing does happen. A logician would say that it contains no causal information.

packed place

Imagine that, instead of talking about why we get fat, we're talking about why a room gets crowded.

Now the energy we're discussing is contained in entire people rather than just their fat tissue.

Ten people contain so much energy, eleven people contain more, and so on. So what we want to know is why this room is crowded and so overstuffed with energy- that is, people.

If you asked me this question, and I said, Well, because more people entered the room than left it, you'd probably think I was being a wise guy or an idiot.
Of course more people entered than left, you'd say. That's obvious. But why? And, in fact, saying that a room gets crowded because more people are entering than leaving it is redundant-saying the same thing in two different ways-and so meaningless.

Now, borrowing the logic of the conventional wisdom of obesity, I want to clarify this point.
So I say, Listen, those rooms that have more people enter them than leave them will become more crowded. There's no getting around the laws of thermodynamics.

You'd still say, Yes, but so what? Or at least I hope you would, because I still haven't given you any causal information. This is what happens when thermodynamics is used to conclude that overeating makes us fat.

eating snack

The National Institutes of Health says on its website, “Obesity occurs when a person consumes more calories from food than he or she burns.”

By using the word “occurs,” the NIH experts are not actually saying that overeating is the cause, only a necessary condition. 

They're being technically correct, but now it's up to us to say, Okay, so what? Aren't you going to tell us why obesity occurs, rather than tell us what else happens when it does occur? "

(Gary Taubes, Why We Get Fat, 2010, Pages 73-75 )

2. The human body is a mass of chemical reactions 

"The first law states that energy can neither be created nor destroyed. In other words, energy can be converted from one form to another, but the total amount of energy in the universe remains constant. How might this law apply to weight management?

Suppose someone has stable weight over time. The first law dictates that, in theory, the number of calories consumed by this individual in the form of food is equal to the calories the individual expends during metabolism and activity. In other words, 'calories in = calories out’.(*snip*)

However, the first law of thermodynamics actually refers to what are known as ‘closed systems' -ones that can exchange heat and energy with their surroundings, but not matter. Is this true for human beings? 

chemical reaction

Actually, no: the human body does indeed exchange matter with its surroundings, principally in the form of the food (matter in) and as waste products such as urine and faeces (matter out). 

Also, technically speaking, the first law refers to systems in which chemical reactions do not take place.

But the human body is essentially a mass of chemical reactions. So, here again, the first law of thermodynamics cannot apply where weight management is concerned.

(Dr.Jone Briffa,Escape the Diet Trap, 2012, pages 63,64  )

3. Calories eaten is not the same as calories the body takes in. My thoughts

Two authors have made excellent points about the relationship between thermodynamics and weight management. Based on those thoughts, I would also like to mention two points about the relationship between thermodynamics and my theory.

(1)What constitutes "caloric intake" 

I also basically believe that if a person has a stable weight over the years, then "the energy consumed  and the energy expended for basal metabolism and activity,etc." must be balanced.
The question, however, is: at what point have we "taken in" energy? 

If we calculate calories at the point we put food in our mouths and consider it "calories consumed," then it is no wonder that for many people it is not balanced with the energy expended.

This is because, as Dr. Briffa pointed out, our bodies are not "closed systems.” If we consider energy absorbed from the gut to be "calories ingested," then it should be considered more of a "closed system."

▽Let's take the example of calcium in milk.

From experience, we know that it is not always true that the more milk we drink, the more calcium we take in and the stronger our bones will become.

Just because a bedridden old lady drinks five glasses of milk a day every two hours every day, does not make her bones stronger; in fact, it sometimes has the opposite effect. Even with just a glass or two of milk a day, exercising more and feeling hungry can increase absorption rate and make her bones stronger. 

In other words, it is not the amount of calcium drunk, but how much calcium is absorbed through the intestines that is balanced against the amount of calcium used in the body(some of the calcium in the blood can be excreted as urine). 

As Dr. Briffa pointed out, our bodies are "a mass of chemical reactions," so what is not absorbed ends up outside the body in the form of fecal matter. 

(2) When energy intake increases

Based on my intestinal starvation mechanism concept, even if a person who has maintained the same weight over the years, significantly reduces their usual caloric intake (e.g., about two thousand kcal daily) and the intake of carbohydrates, but meets the "three factors + one" criteria as I mentioned in another post, they will gain weight (this means an increase in base weight).

[Related article] →Three (+one) Factors to Accelerate “Intestinal Starvation”

Of course, weight gain mostly occurs when the person then goes back to the original diet, but in this case, absorption ability itself goes up, meaning that not only body fat, but also blood and muscle mass,etc. increase, resulting in "weight gain."

In short, even though you are eating the same amount of food (calories) as before, you are taking in more energy and nutrients into your body than before, which means you are getting bigger/fatter.
In the words of Gary Taubes, "a room crowded with ten people now has eleven people," and in this case,
it is “intestinal starvation” that has caused it.

The bottom line

(1) Since the human body is a mass of chemical reactions and not a "closed system," it does not make sense to compare the total calories actually eaten with the calories expended. In this case, the "law of thermodynamics" does not hold.

(2) If we base it on the calories actually absorbed in the intestines, it should be closer to a "closed system" and be balanced with the calories expended through one’s basal metabolism and activity,etc.

(3) If intestinal starvation is induced and your base weight goes up, you will gain weight even if you are eating the same amount as before, which means that the energy taken into the body has increased. Since the absorption ability itself has gone up, the increase in body weight is related to not only body fat, but also blood and muscle mass,etc.


The Calorie Principle and Weight Gain; The Causality Has Been Obscure


  1. The birth of the "calories-in/calories-out" theory 
  2. Obesity is still on the rise
  3. Carl von Noorden's book

In Japan, most people believe that “taking in too many calories and lack of exercise are the causes of being overweight,” which I believe is largely due to statements made by experts, nutritionists, etc. on television.

When I launched this website in 2014, I wanted to argue against that in my website, but I couldn’t find any academic papers and other resources that showed the "causal relationship between caloric intake and becoming obese." 

However, around a year after I started blogging, I came across this great book: “Why We Get Fat” written by Gary Taubes. It is surprising that it was published in Japanese in 2013.

After all, this is the only book I can rely on. In explaining what I want to say, I first needed to let you know that, "the direct cause of being overweight is not determined by overeating.”

1. The birth of the "calories-in/calories-out" theory 

"Ever since the early 1900s, when the German diabetes specialist Carl von Noorden first argued that we get fat because we take in more calories than we expend, experts and non-experts alike have insisted that the laws of thermodynamics somehow dictate this to be true.

Arguing to the contrary, that we might actually get fatter for reasons other than the twin sins of overeating and sedentary behavior, or that we might lose fat without consciously eating less and/or exercising more, has invariably been treated as quackery "emotional and groundless," as the Columbia University physician John Taggart insisted in the 1950s in his introduction to a symposium on obesity.

“We have implicit faith in the validity of the first law of thermodynamics," he added.

Such faith is not misplaced. But that does not mean that the laws of thermodynamics have anything more to say about getting fat than any other law of physics.

Newton's laws of motion, Einstein's relativity, the electrostatic laws, quantum mechanics -they all describe properties of the universe we no longer question.
But they don't tell us why we get fat. They say nothing about it, and this is true of the laws of thermodynamics as well.

It is astounding how much bad science-and so bad advice, and a growing obesity problem-has been the result of the experts' failure to understand this one simple fact. The very notion that we get fat because we consume more calories than we expend would not exist without the misapplied belief that the laws of thermodynamics make it true. (*snip*)

The physicians of Bruch's(German pediatrician that moved to America in 1934) era weren't thoughtless, and the doctors of today are not, either.
They merely have a flawed belief system-a paradigm-that stipulates that the reason we get fat is clear and incontrovertible, as is the cure.

We get fat, our physicians tell us, because we eat too much and/or move too little, and so the cure is to do the opposite. (*snip*)

This is what Bruch described in 1957 as the “prevalent American attitude that the problem (of obesity) is simply one of eating more than the body needs,” and now it's the prevalent attitude worldwide.

We can call this the “calories-in/calories-out” or the “overeating” paradigm of excess fat—the “energy balance” paradigm, if we want to get technical.

“The fundamental cause of obesity and overweight," as the World Health Organization says, “is an energy imbalance between calories consumed on one hand, and calories expended on the other hand." 

We get fat when we take in more energy than we expend (a positive energy balance, in the scientific terminology), and we get lean when we expend more than we take in (a negative energy balance).

Food is energy, and we measure that energy in the form of calories. So, if we take in more calories than we expend, we get fatter. If we take in fewer calories, we get leaner.

This way of thinking about our weight is so compelling and so pervasive that it is virtually impossible nowadays not to believe it.

Even if we have plenty of evidence to the contraryno matter how much of our lives we've spent consciously trying to eat less and exercise more without success— it's more likely that we'll question our own judgment and our own willpower than we will this notion that our adiposity is determined by how many calories we consume and expend. "

(Gary Taubes, Why We Get Fat, 2010, Pages 7,8,73)

2. Obesity is still on the rise

"Consider the obesity epidemic. Here we are as a population getting fatter and fatter.

Fifty years ago, one in every eight or nine Americans would have been officially considered obese, and today it's one in every three. Two in three are now considered overweight, which means they’re carrying around more weight than the public-health authorities deem to be healthy.

Throughout the decades of this obesity epidemic, the calories-in/calories-out, energy-balance notion has held sway, and so the health officials assume that either we're not paying attention to what they've been telling us -eat less and exercise more-or we just can't help ourselves.

Malcolm Gladwell discussed this paradox in The New Yorker in 1998.
“We have been told that we must not take in more calories than we burn, that we cannot lose weight if we don't exercise consistently," he wrote.
“That few of us are able to actually follow this advice is either our fault or the fault of the advice. Medical orthodoxy, naturally, tends toward the former position. Diet books tend toward the latter. Given how often the medical orthodoxy has been wrong in the past, that position is not, on its face, irrational. It's worth finding out whether it is true.”


(Gary Taubes’s thoughts on the relationship between thermodynamics and weight gain)

Obesity is not a disorder of energy balance or calories-in/ calories-out or overeating, and thermodynamics has nothing to do with it. If we can't understand this, we'll keep falling back into the conventional thinking about why we get fat, and that's precisely the trap, the century-old quagmire, that we're trying to avoid."

(Gary Taubes, Why We Get Fat, 2010, Pages 7,8,73)

3. Carl von Noorden's book

Japanese television programs still continue to show doctors and nutritionists confidently saying, "The cause of weight gain is, of course, overeating or lack of exercise,”which I find disgusting. However, I hope you can see how flimsy and baseless these theories are.

By the way, I obtained Carl von Noorden's book (archive), which is shown at the beginning of the quotation. You can read it at the following link: 

 Carl von Noorden's book



The Combination of Undernutrition and Obesity Among the Poor Can be Possible


  1. The case of undernutrition and obesity
  2. What should we do?
  3. Underweight and overweight can coexist. My thoughts

Most of the parts of this article are citations from a book, but at the end of this article, I will explain how it is related to my experience.

[Related article] → Wealthy Ones Get Fat? Poor Ones Get Fat?


1. The case of undernutrition and obesity

"This combination of obesity and malnutrition or undernutrition (not enough calories) existing in the same populations is something that authorities today talk about as though it were a new phenomenon, but it's not. Here we have malnutrition or undernutrition coexisting with obesity in the same population eighty years ago.

(In the mid-1930s, New York City)

In 1934, a young German pediatrician named Hilde Bruch moved to America, settled in New York city, and was “startled,” as she later wrote, by the number of fat children she saw—“really fat ones, not only in clinics, but on the streets and subways, and in schools.”

But this was New York City in the mid-1930s. This was two decades before the first Kentucky Fried Chicken and McDonald's franchises, when fast food as we know it today was born. This was half a century before supersizing and high-fructose corn syrup.

More to the point, 1934 was the depths of the Great Depression, an era of soup kitchens, bread lines, and unprecedented unemployment.

One in every four workers in the United States was unemployed. Six out of every ten Americans were living in poverty. In New York City, where Bruch and her fellow immigrants were astonished by the adiposity of the local children, one in four children were said to be malnourished. How could this be?

It was hard to avoid, Bruch said, the simple fact that these children had, after all, spent their entire lives trying to eat in moderation and so control their weight, or at least thinking about eating less than they did, and yet they remained obese.


(The case of a native American tribe, the Sioux)

A quarter-century after Russell and Hrdlička visited the Pima, two researchers from the University of Chicago studied another Native American tribe, the Sioux living on the South Dakota Crow Creek Reservation.
Fifteen families, with thirty-two children among them, lived “chiefly on bread and coffee.” This was poverty almost beyond our imagination today.

Yet their obesity rates were not much different from what we have today in the midst of our epidemic: 40 percent of the adult women on the reservation, more than a quarter of the men, and 10 percent of the children, according to the University of Chicago report, “would be termed distinctly fat.”

It could be argued that maybe their reservation life of what Hrdlička had called “not a little indolence” was causing their obesity, but the researchers noted another pertinent fact about these Sioux:
one-fifth of the adult women, a quarter of the men, and a quarter of the children were “extremely thin."


The diets on the reservation, much of which, once again, came from government rations, were deficient in calories, as well as protein and essential vitamins and minerals. The impact of these dietary deficiencies was hard to miss: “Although no counts were taken, even a casual observer could not fail to note the great prevalence of decayed teeth, of bow legs, and of sore eyes and blindness among these families.”


(In the slums of São Paulo, Brazil)

This is from a 2005 New England Journal of Medicine article, “A Nutrition Paradox-Underweight and Obesity in Developing Countries,” written by Benjamin Caballero, head of the Center for Human Nutrition at Johns Hopkins University.

Caballero describes his visit to a clinic in the slums of São Paulo, Brazil. The waiting room, he writes, was “full of mothers with thin, stunted young children, exhibiting the typical signs of chronic undernutrition.

Their appearance, sadly, would surprise few who visit poor urban areas in the developing world. What might come as a surprise is that many of the mothers holding those undernourished infants were themselves overweight.”

If we believe that these mothers were overweight because they ate too much, and we know the children are thin and stunted because they're not getting enough food, then we're assuming that the mothers were consuming superfluous calories that they could have given to their children to allow them to thrive.

In other words, the mothers are willing to starve their children so that they themselves can overeat. This goes against everything we know about maternal behavior.

Caballero then describes the difficulty that he believed this phenomenon presents: “The coexistence of underweight and overweight poses a challenge to public health programs, since the aims of programs to reduce undernutrition are obviously in conflict with those for obesity prevention.”

Put simply, if we want to prevent obesity, we have to get people to eat less, but if we want to prevent undernutrition, we have to make more food available. What do we do?

(Gary Taubes, Why We Get Fat, 2010, Pages 3-4, 30-31)

2. What should we do?

"In the early 1970s, nutritionists and research-minded physicians would discuss the observations of high levels of obesity in these poor populations, and they would occasionally do so with an open mind as to the cause.

Here's Rolf Richards, the British-turned-Jamaican diabetes specialist, discussing the evidence and the quandary of obesity and poverty in 1974, and doing so without any preconceptions:
It is difficult to explain the high frequency of obesity seen in a relatively impecunious [very poor] society such as exists in the West Indies, when compared to the standard of living enjoyed in the more developed countries.

Malnutrition and subnutrition are common disorders in the first two years of life in these areas, and account for almost 25 per cent of all admissions to pediatric wards in Jamaica. Subnutrition continues in early childhood to the early teens. Obesity begins to manifest itself in the female population from the 25th year of life and reaches enormous proportions from 30 onwards.

When Richards says “subnutrition,” he means there wasn't enough food. From birth through the early teens, West Indian children were exceptionally thin, and their growth was stunted. They needed more food, not just more nutritious food. 

Then obesity manifested itself, particularly among women, and exploded in these individuals as they reached maturity. This is the combination we saw among the Sioux in 1928 and later in Chile— malnutrition and/or undernutrition or subnutrition coexisting in the same population with obesity, often even in the same families.

▽Referring to obesity as a “form of malnutrition” comes with no moral judgments attached, no belief system, no veiled insinuations of gluttony and sloth. It merely says that something is wrong with the food supply and it might behoove us to find out what.

the coexistence of underweight and overweight in the same populations and even in the same families doesn't pose a challenge to public-health programs; it poses a challenge to our beliefs about the cause of obesity and overweight.

(Gary Taubes, Why We Get Fat, 2010, Pages 29-32)

3. Underweight and overweight can coexist. My thoughts

I will explain that underweight and overweight can coexist through the content mentioned earlier in “The coexistence of being underweight and overweight poses a challenge to public health programs.”

<About undernutrition and overweight>

I repeat that when I was very thin, under forty kilograms, at first, I was eating a lot of high-calorie foods such as deep-fried foods or cheese, but I couldn’t gain weight. And then, I realized that I could gain weight by digesting all the foods in my whole intestines and inducing intestinal starvation.

The easiest way to induce intestinal starvation was to eat refined carbohydrates (starches) and a little easy-to-digest protein (and not to eat other foods), but since it lacked vegetables and minerals, I felt dizzy from the undernutrition.

If I ate milk, cheese, eggs, vegetables, beans and fish to add nutrition and minerals, though the nutrition was better, I couldn’t gain any weight. For me, it was because I couldn’t digest them well. 

In short, a high ratio of carbs in the meal (not an amount of carbs) and not eating nutritious foods that contain fiber and fat are more likely to induce intestinal starvation and cause you to gain weight. It’s probably certain that a deficiency of vitamins and/or minerals can cause illnesses, but being overweight is not contradicting being in a state of undernutrition.

<About the coexistence of being underweight and overweight>

Getting back to what Caballero refered to, even if people eat similar foods in the same group, it may lead to a different result in the body.
Some people who digested all the foods in their whole intestines may have gained weight—which means their base weight value went up— and ended up becoming overweight. (As their body becomes bigger, they are prone to have a greater appetite. They can digest foods faster than thin people)

However, those who were not able to digest all the foods in their whole intestines remained underweight. I believe that leaving Just a little bit of undigested food in the intestines doesn’t induce intestinal starvation. (Being extremely thin can cause poor digestion, so it makes it hard for them to induce intestinal starvation). A small difference sometimes makes a big difference in the end result. 

To sum up, what happened in the groups in poverty situations is a similar phenomenon that is happening in our modern society. Some people are overweight (even if they eat a little), but others are thin regardless of caloric intake.

At the risk of repeating myself again, but being overweight or obese is not the consequence of overeating. 


How the number of meals affects obesity?


  1. The relationship between the number of meals and weight gain
  2. How many meals a day makes you fat the most?
  3. Can eating more often help you lose weight?
  4. Cause and effect are sometimes reversed


(1) If you take into account the fact that “the phrase ‘to gain weight’ has two meanings”, there are several possible patterns.
[related article]→ 2 meanings to the phrase "gaining weight"

(2) One or two meals a day tend to make you gain weight in the long term, but the number of meals alone does not decide if you will gain weight. The most important thing is "what to eat” and other factors can also influence.

(3) Increasing the number of meals may help you lose weight.

(4) Studies that only examine the relationship between the number of meals and obesity are useless. A reverse causality may arise when people are already big or overweight and thus eat four to five meals a day.

1. The relationship between the number of meals and weight gain is not so simple

Some experts say that if the total calorie you take in a day is the same, then "how many meals you eat a day does not matter," but I definitely insist that the number and timing of your meals can affect your weight gain (or loss). 

I mentioned that the phrase "to gain weight" has two meanings, so let me explain part (A) first.

Many people think that “taking in more calories makes you gain weight”, which means going back to their Base Weight(BW).

In this case, it’s nothing to do with “how many meals you eat a day".
But people who usually be on a diet and keep their weight lower, or who endure hunger in a long time, may gain weight if they eat more calories than they need.

As for part (B), the opposite is true: Since it is the mechanism of hunger (strictly speaking, intestinal starvation) that increases the BW itself, eating more often and taking in more calories do not mean increasing the BW.
Rather, taking in the same calories by eating more often is less likely to lead to weight gain. When you feel hungry, foods enter your stomach again, which means that undigested foods are more likely to remain in your stomach and intestines. 

Therefore, eating four or five times a day for thin people to gain weight is counterproductive.
Also, for people who want to lose weight, skipping breakfast or lunch in order to reduce calories intake and eating only two meals a day while putting up with hunger can easily increase their BW in the long run. Thus, it may lead to the opposite result.

2. How many meals a day makes you fat the most?

Based on my idea, people tend to gain weight (that means their BW increases) 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. And conversely, even if you eat four or five meals a day, you will not always lose weight. 

It is pointless to argue that only in terms of “how many meals a day you eat”. If I explain this relationship from the perspective of the intestinal starvation mechanism, “how many meals you eat a day” actually means "meal intervals", and that is not the deciding factor for gaining weight. The most important thing is "what to eat (quality and balance of foods)”.


(three balanced meals a day ↑↑)

(three unbalanced meals a day ↑↑)

Others that may affect are "timing of eating (e.g., is lunch at 12 pm or 2 pm?)" and a person's "digestive power". This mean that, even if they eat exactly the same foods in the same way, people who can digest them faster make the state of intestinal starvation faster.

[related article]→ What does it mean to eat relatively less?

■A friend of mine who gained weight only with one meal a day

A friend of mine in college worked part-time in a restaurant. He ate only the meal for employee there and nothing else, so he had one meal a day.

(His meals there were often a bowl of rice and a few side dishes, miso soup, etc.)

He gained about 10 kilograms since he started working. He once could not gain weight even though he was eating three meals a day and more calories, in high school (i.e. this is not a calorie issue).

■A friend of mine who gained weight by eating four to five meals a day

Another friend of mine gained more than 10 kilograms by eating four to five meals a day when he was studying for a college entrance exam after graduating from high school. He belonged to a judo(Japan’s national sport) club in high school, and was very thin even though he ate a lot. 

But please note that it is not the five meals a day that make you fat, but what you eat (quality and balance of foods) and how you eat that matter. He told me that light meals such as sweet bread, rice balls, and cup noodles made up more than half of his meals.

If even a light meal such as a pastry, hamburger, or rice ball counts as "one meal", how many meals you eat a day does not account for the result.

3. Can eating more often help you lose weight?

Although what you eat is the most important thing, and I cannot make an assertion only based on the number of meals, I believe that increasing the number of meals a day is one right way to lose weight soundly.

According to a study by Professor Imai and her group at Osaka University (2016), there was a change in blood sugar levels in diabetic patients depending on what time of day they ate cookies.

The results of the experiment showed that eating cookies between meals kept the peak blood sugar levels lower than eating them just after a meal.

This is an experiment with a snack, but you can change cookies with a bit heavier diet, like cheese, fried mushrooms in oil, or even sautéed meat.

Please don’t get me wrong. I am not saying that it helps you lose weight because it is less likely to raise your blood sugar levels.

Rather than enduring hunger for a long time and eating with a bang, snacking throughout a day in order not to create hunger leaves more "undigested" food in your intestines and reduces “absorption rate” first, which results in less blood sugar levels.  I believe reducing “absorption rate” is more crucial in regard to losing weight.

4. Cause and effect are sometimes reversed

In some cases, studies only about “the number of meals” may tell a lie.
For example, suppose you surveyed overweight and obese people and asked them how many meals a day they eat. Let's assume that most of them answered four to five times. But you cannot take the overall results and say “eating four or five times a day is likely to make you gain weight”. 

The reason for this, as I said earlier, is that the most important things are missing: what you eat, how you eat, and how much you eat, etc. Additionally, as your body gets bigger, your stomach and intestines also become bigger and have more digestive power, so it is natural that you feel hungry faster even if you eat the same amount as others.

In other words, it is not because you eat more often that you gain weight, but because you have a bigger body, and thus you may end up eating more frequently than others as you cannot put up with hunger. Therefore, in this case, the cause and effect are the opposite.


Does eating late at night really make you fat? (chrono-nutrition)


  1. It's natural to gain weight by eating at night
  2. When late night eating habits lead to weight gain
  3. It's impossible to explain it with BMAL1
  4. Eating before going to bed does not cause weight gain

In Japan, many people (especially women) tend to avoid eating dinner, a dessert or sweets late at night (after 9 pm) because they do not want to "gain weight". But does it really make sense?

In fact, some people say that they have started eating dinner late at night and gained more weight than before, but I believe there is a false perception.


The phrase "gaining weight" has two meanings, and therefore there may be several patterns; surveys and studies based on only one viewpoint cannot capture the whole picture.

[related article]→2 meanings to the phrase "gaining weight"

(1) In a sense, everyone should be more likely to gain weight if they eat at night, since bones, muscles, and body fat are made mainly while they are sleeping. Especially people who usually take fewer calories to lose weight tend to gain weight when taking more calories than necessary. But in this case, it does not matter whether they eat at 7 pm or 10 pm.

(2) In terms of my intestinal starvation theory, late night eating habits can lead to increase in weight. Those people tend to skip breakfast and eat two meals a day. They may also find it difficult to eat a balanced meal late at night and the meal might be skewed towards carbohydrates, meat and junk food.
In other words, it is because eating late at night has a significant effect on "what to eat" and "meal intervals".

(3) It is impossible to correlate the secretion of BMAL1, a protein of the "clock gene" that promotes fat synthesis, with weight gain. It would be meaningless to compare the time of eating with the amount of secretion.

(4) For some thin people, eating a heavy meal before sleeping in addition to the three meals would rather work in the direction of losing weight. Energy is used more towards digestion, which should reduce the absorption of nutrients and synthesis of cells.

1. In a sense, it is natural to gain weight by eating at night

While we are sleeping at night, our bodies are not resting. They are doing something very important to our bodies while we are sleeping. I will not go into details here, but it is said that there are two main things:

One is the removal of waste products from the brain and the organization and consolidation of memory.

The other is body maintenance and cell regeneration. The secretion of "growth hormones" stimulates metabolism, repairs damaged cells throughout the body, recovers from fatigue, and improves the immune system. It is also said that various enzymes and tissues such as bones, muscles, and body fat are produced. 

Thus, in a sense, isn't it natural that eating late at night tend to make everyone gain weight? If you are on a diet regularly, you will realize that if you eat more calories than you need and go to bed, you will rebound a few kilograms per night. But that is when your present weight go back to your Base Weight (see Figure below), and in this case, it does not matter what time of night you eat.

2. When late night eating habits lead to weight gain

I sometimes hear people say "I did not gain weight when I ate dinner around 7 pm, but after working overtime and eating at 10 pm at night, I gradually gained weight. But that is a separate issue from [1] above, and is a case of Base Weight itself going up in my intestinal starvation theory.

First of all, many people tend to skip breakfast if they eat dinner late at night. This means they only have two meals, lunch and dinner. Also, getting home late at night and then finding a well-balanced meal can be difficult.

Unless their wife prepares a meal for them, they will end up eating ramen, curry, beef bowl, etc. which they get at a convenience store or at a restaurant that is open till late.

This means they will end up eating a high-calorie, nutritionally unbalanced meal.

In other words, eating dinner late has a great impact on "what to eat" and "meal intervals".
And in this case,
eating late is not a "cause" of weight gain. It’s a "consequence". The cause for this is an unbalanced diet skewed towards carbohydrates and meat(/fish), and putting up with hunger for hours by skipping breakfast, etc. 

▽One way to prevent this is to diversify meals, such as having a sandwich, cookies, or milk around 5 pm if dinner is going to be late. You should also try to eat a balanced diet.

3. It is impossible to explain it with BMAL1

Many Japanese experts confuse the two meanings of [1] and [2], stating as if secretion volume of BMAL1 and weight gain are correlated. 

BMAL1 is a protein of the "clock gene" that promotes fat synthesis, and its secretion increases around 6 pm and peaks between 10 pm and 2 am, which seems to be thought as a rational behind the fact that people are several times more likely to gain weight if they eat late at night than during the day for the same calories.

However, I think that explanation is a bit of a stretch. The reason is that the "digestion time" is missing.

For example, if they eat a meal at 10 pm, it will take 4-6 hours for it to be digested and absorbed, depending on the person.
Fats are particularly difficult to digest, so they may find that their stomach is still undigested and upset in the morning after 7-8 hours.

In other words, if it is not digested, it cannot be absorbed, so you cannot relate the time you eat it to your BMAL1 value.

In my guess, the reason why BMAL1 peaks between 10 pm and 2 am is that if we humans have been eating dinner around 6 pm since ancient times, it peaks at just about the time of finishing digestion and absorption (to be synthesized successfully).

4. Eating before going to bed does not cause weight gain

If they eat breakfast, lunch, and dinner properly, I think, for most people, eating before going to bed does not cause weight gain.

As I said earlier, if you eat a lot of calories than you need, you will definitely gain weight. It means your present weight goes back to your Base Weight. A weight gain might be 2 or 5 kilograms, depending on the person, but it should stop at a certain weight. 

In Japan, there are a lot of people who have gastroptosis or weak stomachs, and even if they eat a dessert, sweets or a light meal before bedtime in addition to the three meals to gain weight, their bodies might still work in the direction of slimming down rather than gaining weight (at least, it is true for me).

By nature, it is good to rest your body and your stomach while you sleep, but if you eat before going to bed, your stomach has to continue to work while you sleep. I believe that this reduces absorption capacity and cell regeneration.