First, as many of you know, even carbohydrates contain four kcal of energy per gram. So, some readers may think, "After all, isn't being overweight ultimately caused by too many calories?"

But if you think, "too many calories are the cause," you should try to reduce the total amount of calories in your overall diet, mostly focusing on fat/oil intake, which has nine kcal per gram.

On the other hand, the argument that “too many carbohydrates cause weight gain” allows you to eat any amount of meat and fatty/oily foods as long as you cut back on carbs.

In this article, I will look back on the historical argument of whether carbohydrates or calories are the cause of weight gain, and at the end of this article, I would like to share my thoughts.

In Japan, a low-carb diet was trendy around 2015, but when we look around the world, this way was repeatedly conducted since the 1800’s. Please note that there are many quoted parts. I needed to share this information with you to explain my theory.
  

"Jean Anthelme Brillat-Savarin was born in 1755. (*snip*) His passion, though, was always food and drink, or what he called the “pleasures of the table.” He began writing down his thoughts on the subject in the 1790s; Brillat-Savarin published them in a book, The Physiology of Taste, in December 1825. (*snip*)

“Tell me what you eat,” Brillat-Savarin memorably wrote, “and I shall tell you what you are." (*snip*)

Over the course of thirty years, he wrote, he had held more than five hundred conversations with dinner companions who were “threatened or afflicted with obesity,” one “fat man” after another, declaring their devotion to bread, rice, pasta, and potatoes. This led Brillat-Savarin to conclude that the roots of obesity were obvious. 

(*snip*)
"By the time, a French physician and retired military surgeon named Jean-Francois Dancel had come to the same conclusions as his countryman Brillat-Savarin. Dancel  presented his thoughts on obesity in 1844 to the French Academy of Sciences and then published a book, Obesity, or Excessive Corpulence: The Various Causes and the Rational Means of a Cure.

Dancel claimed that he could cure obesity “without a single exception” if he could induce his patients to live “chiefly upon meat," and partake “only of a small quantity of other food." 

Dancel argued that physicians of his era believed obesity to be incurable because the diets they prescribed to cure it were precisely those that happened to cause it. (*snip*)

"Until the early years of the twentieth century, physicians typically considered obesity a disease, and a virtually incurable one, against which, as with cancer, it was reasonable to try anything. Inducing patients to eat less and/or exercise more was just one of many treatments that might be considered. (*snip*)
    

<1950's>
The effects of a carbohydrate-restricted diets were then confirmed in the 1950s by Margaret Ohlson, head of the nutrition department at Michigan State University, and by her student Charlotte Young. 

When overweight students were put on conventional semi-starvation diets, Ohlson reported, they lost little weight and “reported a lack of ‘pep’ throughout... [and] they were discouraged because they were always conscious of being hungry.” 

As you can see, by cutting back on carbohydrates and eating more of other foods such as meat and greasy food, the problem of being overweight seems to be solved...but this is where the "calorie principle" comes into play. 
   

"By the 1960s, obesity had come to be perceived as an eating disorder. (*snip*)

 Adiposity 101 was discussed in the physiology, endocrinology, and biochemistry journals, but rarely crossed over into the medical journals or the literature on obesity itself. 

When it did, as in a lengthy article in The Journal of the American Medical Association in 1963, it was ignored. Few doctors were willing to accept a cure for obesity predicated on the notion that fat people can eat large portions of any food, let alone as much as they want. This simply ran contrary to what had now come to be accepted as the obvious reason why fat people get fat to begin with, that they eat too much. 

I ‘d like to talk about this controversy.

Several studies have shown that how we combine the three macronutrients (protein, fat, and carbohydrates) in the diet produces different results in body fat accumulation. It is thought that even the same one calorie has different energy used for digestion and absorption, different hormones to stimulate, and different pathways of how the calorie is metabolized in the body.

Of course I think these studies are great, but the point I'd like to add based on my theory is that "carbohydrates and fat are close to having opposite properties in their digestive processes."

First, refined carbohydrates are more easily digested than meats and fats, and the "dilution effect" or "push-out effect" they have makes our digestion go even faster and makes us feel hungrier.

If we eat an unbalanced diet that lacks vegetables, fat, and dairy products,etc., we are ultimately more prone to inducing intestinal starvation.

That is to say, depending on how we structure our diets, there may be a weight-loss effect even with increased caloric intake (for those who can digest protein and fat quickly, the weight-loss effect may be less pronounced) .
   

(1) From the early 1800’s through the 1960’s, several studies had shown that overweight people could lose weight without difficulty by replacing some carbohydrates in their diet with a lot of meat and fat. By that time, however, obesity was understood as an eating disorder, and this diet method was discussed only in physiology, endocrinology, etc.

(2) From the 1960’s to the late 1970’s, few physicians accepted the idea that fat people could lose weight by eating lots of meat and fat, because it obviously violated the "calorie principle.”

(3) In addition, health experts came to believe that fat in the diet caused heart disease and that carbohydrates were "heart-healthy." As a result, doctors and nutritionists began attacking low-carb diets.

(4) My thoughts: Both sides have a point, but the caloric intake does not determine everything. Different combinations of foods, even with the same calories, have different effects on weight management. In particular, carbohydrates and fat are close to having opposite properties in their digestive processes.