It is a staple that has sustained civilizations over centuries and is intrinsically etched into the very grains of society. However, as obesity rates continue to rise, it may now be time to retire this dependency in modern diets.
Obesity is a risk factor for many lifestyle-related diseases, so it has become paramount to prevent its further spread. Previous obesity research has mainly focused on excessive fat intake as the primary cause, thus prompting the use of high-fat diets in animal models. In contrast, carbohydrates, such as bread, rice, and noodles, are consumed daily as staple foods, but there is limited research examining their effects on obesity and metabolism. Furthermore, while "bread makes you gain weight" and "carbohydrates should be limited" are common perceptions, it has remained unclear whether this is due to the inherent properties of the food itself or to changes in dietary preferences and eating habits.
To knead out these unknowns, a research team led by Professor Shigenobu Matsumura at Osaka Metropolitan University's Graduate School of Human Life and Ecology investigated whether carbohydrates, such as wheat, bread, and rice, are preferred by mice over standard chow, and how the consumption of these foods affects energy metabolism and weight regulation. The team then sifted deeper and established a system that divided the mice into feeding groups, Chow, Chow + Bread, Chow + Wheat flour, Chow + Rice flour, High-fat diet (HFD) + Chow, and HFD + Wheat flour. Changes in body weight, energy expenditure, blood metabolites, and gene expression in the liver were analyzed.
Results revealed that the mice exhibited a strong preference for carbohydrates and altogether stopped consuming the standard chow. Under these conditions, body weight and fat mass increased, even though total caloric intake did not increase significantly. Furthermore, in the rice flour intake group, weight gain occurred in the same manner as wheat flour. Conversely, mice in the HFD + wheat flour group exhibited less weight gain compared to those in the HFD + chow group.
"These findings suggest that weight gain may not be due to wheat-specific effects, but rather to a strong preference for carbohydrates and the associated metabolic changes," said Professor Matsumura.
In addition, this study conducted indirect calorimetry using respiratory gas analysis. The results indicated that weight gain was not due to "overeating," but rather due to a decrease in energy expenditure. Furthermore, analysis of blood metabolites revealed increased levels of fatty acids and decreased levels of essential amino acids. In the liver, there was an accumulation of fat and increased expression of genes involved in fatty acid synthesis and lipid transport. When wheat flour intake was discontinued, weight and metabolic abnormalities quickly improved. This demonstrates that switching from a wheat-based diet to a more balanced one makes it easier to control body weight.
"Going forward, we plan to shift our research focus to humans to verify the extent to which the metabolic changes identified in this study apply to actual dietary habits," stated Professor Matsumura. "We also intend to investigate how factors such as whole grains, unrefined grains, and foods rich in dietary fiber, as well as their combinations with proteins and fats, food processing methods, and timing of consumption, affect metabolic responses to carbohydrate intake. In the future, we hope this will serve as a scientific foundation for achieving a balance between "taste" and "health" in the fields of nutritional guidance, food education, and food development."
The findings were published in Molecular Nutrition & Food Research.
