High-fat foods are tasty and high in calories, and can easily lead to excessive consumption, promoting overweight and obesity. What about carbs, though? Bread and pasta are also tasty foods, but how much do they influence the risk of putting on unwanted kilos? Not a little, at least according to a new study carried out by researchers at Osaka Metropolitan University and published in the journal Molecular Nutrition & Food Research. In fact, bread, wheat and rice flour seem to promote weight gain even without increasing caloric intake, altering the metabolism and reducing the body’s energy consumption. Results obtained so far on mice, and awaiting confirmation in our species.
The role of carbohydrates
Traditionally, the focus of research on the dietary causes of obesity has been on fats. The latter are known for their high calorie density and ability to stimulate the brain’s reward system, leading to excessive consumption. However, the impact of carbohydrates, and in particular wheat derivatives such as bread and pasta, remains an open and debated field of investigation. The authors of the research observed that, in recent decades, wheat consumption has increased globally in parallel with obesity rates. To understand whether there was a direct causal link, they decided to carry out a comparative experiment to isolate the effects of wheat from those of other macronutrients.
Comparison of diets
The experiment involved groups of mice fed different diets. The first group received a standard diet, while the others were fed high-fat or high-carb variants (bread, wheat flour and rice flour). Mice fed bread, wheat or rice flour gained weight more rapidly than those fed the high-fat diet. A crucial aspect of the study was the control of calorie intake: the carbohydrate-fed mice did not consume more calories than the control group. This data suggests that the weight gain was not caused by overeating, but by how the body processed the ingested substances.
Metabolic alterations and energy expenditure
Researchers have tried to identify the physiological causes of this fat accumulation. Through the use of metabolic chambers, the animals’ oxygen consumption and carbon dioxide production were monitored. The results indicated that the mice fed wheat had a lower basal energy expenditure: their metabolism was slowed, which is why they burned fewer calories and tended to gain weight.
Furthermore, the study highlighted changes in the expression of some genes linked to lipid metabolism in the liver and adipose tissue. In particular, a reduction in fatty acid oxidation was observed, suggesting that the animals’ bodies tended to store fat instead of using it as fuel.
The limits of the research
Although the findings are statistically significant, the authors urge caution when extending these conclusions to humans. Murine physiology presents substantial differences compared to human physiology, especially in the way in which cereals are metabolised. The hypothesis that carbohydrates induce weight gain by altering basal metabolism still needs to be verified through controlled clinical studies on our species.
Furthermore, it is not yet clear which specific component of wheat – whether proteins such as gluten or particular starch fractions – is responsible for this effect. At the current state of knowledge, a balanced diet and portion monitoring remain the main tools for maintaining metabolic health and weight control.