A study found that a child's risk of obesity may increase just from a mother being exposed to certain food smells during pregnancy and breastfeeding. While a mother's high-fat diet has been seen to raise a child's obesity risk because of calories or nutrients, sensory information such as the aroma of food can also affect metabolism.
A research team led by Sophie M. Steculorum, a group leader at the Max Planck Institute for Metabolism Research in Germany, published a paper on the 2nd in the international journal Nature Metabolism saying that exposure to certain food smells during pregnancy can cause long-term changes in offspring's metabolism.
Food contains not only calories and nutrients but also volatile compounds that diffuse into the air, that is, odor components. These odor components can be delivered to fetuses and newborns through amniotic fluid or breast milk. Transfer research has reported that such sensory stimuli affect the formation of children's food preferences, but it has not been clear whether they can actually change the risk of metabolic diseases such as obesity or diabetes.
To confirm this, the researchers fed pregnant mice either regular chow or chow with identical nutrients but with added bacon flavor. This allowed them to rule out the effects of calories and nutrients and observe the effects of sensory signals such as smells and aromas separately.
As a result, there was no difference in the mother mice's weight gain during pregnancy or in fetal growth. However, the pups exposed to the bacon aroma accumulated more body fat, had higher insulin resistance, and showed reduced energy expenditure after reaching adulthood and eating a high-fat diet. Even on the same high-fat diet, the mice exposed to the smell became bodies that gained weight much more easily. Insulin resistance is a condition in which insulin, which controls blood sugar, does not work properly and is a factor that raises the risk of diabetes.
The researchers found the reason through brain analysis. In the brains of mice exposed to the bacon aroma, activity in the "reward circuit," the area that regulates the pleasure of eating, and in appetite-related neurons changed to resemble the brain responses of obese mice.
Simply put, sensory stimuli such as food smells during early pregnancy and breastfeeding pre-train the brain's eating habits and set the metabolic profile like a program.
The researchers said, "These findings suggest that sensory stimuli experienced early in life, especially during fetal and newborn periods, can determine lifelong energy metabolic health," but noted, "Because the experiments were conducted in mice, further research is needed to see whether this applies directly to humans."
References
Nature Metabolism (2025), DOI: https://doi.org/10.1038/s42255-025-01405-8