Researchers at Osaka Metropolitan University discovered that mice strongly prefer carbohydrate-rich foods like bread and rice, leading to weight gain even without increased calorie intake. The animals burned less energy, accumulating fat due to metabolic changes. The findings challenge assumptions about carbs and obesity.
A team led by Professor Shigenobu Matsumura at Osaka Metropolitan University's Graduate School of Human Life and Ecology conducted experiments on mice to explore the effects of staple carbohydrates on metabolism and body weight. The mice were offered standard chow alongside options like bread, wheat flour, or rice flour, or combined with high-fat diets. They overwhelmingly chose the carb-rich foods, abandoning their regular diet, yet total calorie consumption remained similar to controls. Despite this, body weight and fat mass increased significantly in groups consuming wheat or rice flour with chow. Mice on high-fat diets with wheat flour gained less weight than those without it, suggesting carbs drive the effect rather than wheat specifically. Professor Matsumura stated, '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.' Indirect calorimetry revealed reduced energy expenditure as the key factor, not overeating. Blood tests showed elevated fatty acids and depleted essential amino acids, while livers accumulated fat with upregulated genes for fatty acid production and transport. Removing wheat flour rapidly reversed weight gain and metabolic issues. The study appears in Molecular Nutrition & Food Research. Professor Matsumura plans human trials to assess if these carb-induced changes apply beyond mice, including effects of whole grains, fiber, proteins, fats, processing, and meal timing.
