Researchers at Osaka Metropolitan University have found that diets heavy in carbohydrates, such as bread and rice, can cause weight gain by reducing energy expenditure rather than through overeating.
A study led by Professor Shigenostu Matsumura at the university's Graduate School of Human Life and Ecology tracked mice that were given preferences for wheat, bread, and rice over standard chow.
The mice transitioned to these carbohydrate-rich foods and eventually abandoned their regular diet entirely. Despite maintaining a similar total calorie intake, the animals showed significant increases in both body weight and fat mass.
Metabolic changes drive fat accumulation
Using respiratory gas analysis, the research team determined that the weight gain resulted from a reduction in energy use. The study observed higher levels of fatty acids in the blood and increased fat accumulation in the liver.
"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," Matsumura said.
The study also noted that mice consuming rice flour experienced weight gain similar to those eating wheat flour. In contrast, mice on a high-fat diet paired with wheat flour gained less weight than those on a high-fat diet with standard chow.
Researchers observed that metabolic abnormalities and body weight improved quickly once wheat flour was removed from the diet. This suggests that a shift toward a more balanced diet can help regulate weight.
Professor Matsumura stated that the next phase of research will focus on humans to see if these metabolic changes apply to actual human dietary habits. The team also plans to investigate how fiber, protein, and food processing methods affect these metabolic responses.
