Bread has long been a cornerstone of the diet and has sustained society for generations. It is deeply woven into everyday life. But as obesity rates continue to rise, researchers are beginning to question whether this reliance on staple carbohydrates still makes sense in modern diets.
Obesity increases the risk of many lifestyle diseases, making prevention a major public health priority. Traditionally, research has focused on high fat intake as the main factor in weight gain. This is why many animal studies rely on high-fat diets.
However, although carbohydrates such as bread, rice, and noodles are consumed daily around the world, their role in obesity and metabolism has not been studied as thoroughly. Many people believe that bread makes you fat and that carbohydrates should be limited, but it is unclear whether the problem lies with the food itself or with the way people choose and consume it.
A study investigating carbohydrate preference and its effects on metabolism
To better understand these questions, a research team led by Professor Shigenobu Matsumura of the Osaka Metropolitan University Graduate School of Life and Ecology studied how carbohydrates affect the feeding behavior and metabolism of mice.
The researchers investigated whether mice preferred foods such as wheat, bread and rice over a standard diet, and how these choices affected their body weight and energy expenditure. Animals were divided into several feeding groups, including chow, chow + bread, chow + flour, chow + rice flour, high-fat diet (HFD) + chow, and HFD + flour. The researchers tracked changes in body weight, energy expenditure, blood metabolites, and liver gene expression.
Carbohydrate preference leads to weight gain without adding calories
The results showed that the mice had a strong preference for carbohydrate-rich foods and stopped eating standard food altogether. Body weight and fat mass both increased, although total calorie intake did not increase significantly.
Mice that consumed rice flour gained weight similar to mice that consumed wheat flour. In contrast, mice fed a high-fat diet (HFD) + wheat flour gained less weight than mice fed a high-fat diet (HFD) + chow.
“These findings suggest that weight gain may not be due to wheat-specific effects, but rather due to a strong preference for carbohydrates and associated metabolic changes,” Professor Matsumura said.
Slower energy use may promote weight gain
The research team also used indirect calorimetry with breathing gas analysis to better understand energy use. The results showed that weight gain was not caused by “overeating” but rather by a decrease in energy expenditure.
Further analysis revealed high levels of fatty acids and low levels of essential amino acids in the blood. In the liver, fat accumulation increased, along with the activity of genes related to fatty acid production and lipid transport.
When flour was removed from the diet, both body weight and metabolic abnormalities improved rapidly. This suggests that moving away from a diet high in wheat and toward a more balanced diet may help regulate weight more effectively.
Next steps: Applying the findings to human diets
Professor Matsumura said, “In the future, we would like to shift our research to humans and verify to what extent the metabolic changes revealed in this study apply to actual dietary habits.” “We also want to investigate how whole grains, unrefined grains, foods rich in dietary fiber, combinations with proteins and fats, food processing methods, and timing of intake affect the metabolic response to carbohydrate intake. In the future, we hope to use this research as a scientific basis for achieving a balance between “tastiness” and “health” in the fields of nutritional guidance, dietary education, and food development.”
The survey results are Molecular nutrition and food research.
