Khaberni - In a scientific surprise that may change many people's view of carbohydrates, a Japanese study revealed that consuming bread and rice could lead to weight gain, even without an increase in total calorie intake.
Researchers at Osaka Metropolitan University, led by Professor Shigenobu Matsumura, decided to go beyond traditional theories focusing on fats as the main driver of obesity and highlight carbohydrates, which dominate daily meals around the world, from bread to rice to pasta.
Scientists have long used high-fat diets in animal studies, because fats were considered the most prominent cause of weight gain. But the Japanese team noticed a significant research gap: carbohydrates are consumed daily and in large quantities, yet their role in obesity and metabolism has not been studied in the same depth. Everyone thinks that "bread causes obesity" or that "carbohydrates should be limited," but the most important question remained unanswered: Is the problem in the carbohydrates themselves, or in the way people choose and consume them?
To answer this question, the researchers designed a clever experiment on mice. They divided them into different groups: one group consumed only standard food, another consumed standard food with added bread, a third with wheat flour, and a fourth with rice flour, in addition to two more groups one of which consumed high-fat food alone, and the other had wheat flour added to high-fat food.
The team then carefully monitored changes in body weight, energy consumption, blood metabolites, and even gene expression in the liver.
The mice showed a very strong preference for carbohydrate-rich foods to the extent that they completely stopped eating their normal standard food. Most surprisingly, although the total calories consumed by these mice did not increase significantly, their body mass and fat actually increased.
Stranger still, the mice that consumed rice flour increased in weight in the same way as the mice that consumed wheat flour, meaning that the problem is not exclusively with wheat.
It turned out that the mice that consumed high-fat food with added wheat flour gained less weight than those that consumed high-fat food alone.
The researchers used an advanced technique called indirect calorimetry along with breath gas analysis to precisely measure energy consumption. The biggest surprise was that the cause of the weight gain was not "overeating," as commonly believed, but rather a decrease in the amount of energy the body burns (energy expenditure), meaning that the body started burning fewer calories than before. This was accompanied by metabolic changes including increased fatty acids in the blood and fat accumulation in the liver. The activity of genes responsible for the production and transportation of fatty acids also increased.
These combined signs paint a clear picture: a carbohydrate-rich diet, even without an increase in calories, reprograms the metabolic process towards fat storage and reduces energy burning.
But the good news is that these changes are not permanent. When the researchers removed wheat flour from the diet, both body weight and metabolic disorders improved noticeably. This suggests that moving away from a carbohydrate-heavy diet towards a more balanced diet could be an effective key to weight regulation.
Now, the Japanese team is planning to move their research from the lab into real life, through human studies to verify how these findings apply to actual eating habits.
These important findings were published in the journal Molecular Nutrition & Food Research.
