There is a surprising factor that could influence obesity risk in offspring. A team of researchers led by neuroscientist Sofia K. Neuner of the Max Planck Institute for Metabolism Research experimented with mice and found that the smell of fatty foods during pregnancy, even without high-fat nutrition, can alter brain circuits controlling hunger and reward, predisposing the next generation to weight gain and metabolic disorders.
Mice Experiment Shows That Prenatal and Early-Life Exposure to Odors From Fatty Food Alters the Metabolic Development of Offspring and Increases Obesity Susceptibility
Prenatal Metabolic Development Factors
Scientists know that unborn offspring can acquire the eating habits of their mothers. This is called prenatal food learning. There is also consensus that early-life factors before birth and just after giving birth can shape long-term metabolic health. These include maternal body composition and maternal eating habits. Neuner and her team explored a new idea.
Note that the team specifically observed something puzzling in human populations. Children in households where fatty, processed foods are frequently present often show increased obesity risk, even when mothers do not necessarily overeat during pregnancy. This hinted that sensory cues and not just calories might influence the metabolism of the children.
The researchers acknowledged the fact that food has non-nutritive sensory components such as volatile odors. Food items that are high in fat also have a distinct chemosensory signature. The team wanted to investigate the consequences of developmental exposure to non-nutritive sensory food cues by focusing on specific fat-related sensory cues.
Previous research also showed that prenatal environment can program metabolism, and that the brain regions controlling appetite are shaped early in life. The researchers wondered if fatty-food smells during pregnancy could send false signals to the fetus to indicate an abundance of fat-rich food and cause the developing brain to prepare for a high-fat environment.
Impact of Exposure to Fatty-Food Odor
Neuner and her team tested their idea by performing experiments on pregnant mice. The mice were grouped into two. These were Group A, the control group composed of mice that were fed with normal and healthy low-fat food, and Group B, the odor-exposed group composed of mice that ate the same healthy low-fat food but were given a fatty-food smell.
Moreover, after giving birth, the baby mice were raised normally with no special treatment. They were tested later in life using a high-fat diet to see how strongly they gained weight and whether their metabolism handled fat poorly. The brains of the offspring population were also examined to look for changes in regions that control appetite and metabolism.
Results revealed that prenatal exposure to fatty-food odors can influence offspring metabolism, even when mothers consume a healthy low-fat diet. The experiment in mice showed that sensory cues can predispose the next generation to obesity and metabolic dysfunction by altering brain circuits controlling hunger and reward. Below are the key findings:
• Healthy Mothers, Altered Offspring: The mothers remained metabolically normal or healthy. This critical finding confirms that the effect arose from odor exposure rather than maternal obesity or nutrient excess from a poor diet.
• Brain Circuit Remodeling: Key brain regions controlling hunger and reward, including dopaminergic circuits and hunger-regulation neurons, were permanently altered in the offspring, resembling patterns seen in naturally obese mice.
• Flavor Additives Trigger Similar Effects: A single food additive that mimics fatty-food aromas produced comparable metabolic programming. This underscores potential and important implications for human processed foods.
• Sensory Cue Necessity: It is important to note that passive exposure to the odor without ingestion did not produce obesity, indicating that the combination of olfactory cues with nutrient intake is critical for metabolic reprogramming.
• Priming for a High-Fat Environment: The offspring population appears metabolically anticipating a high-fat diet. This further suggests how early-life sensory exposure can shape long-term energy balance and susceptibility to obesity.
Further Explanations and Key Takeaways
It is important to note that the unborn offspring does not smell in the same way an adult does, but it can sense chemical cues from the mother. Specifically, when the pregnant mother eats or is exposed to foods with strong odors, small molecules from these foods enter her bloodstream. Some of these molecules can cross the placenta and reach the fetus.
The developing olfactory system and brain of the fetus can detect these chemical signals. The brain interprets them as environmental cues and is essentially learning what types of foods are present. This early exposure influences the development of hunger, reward, and metabolism circuits, thus preparing the body for the type of food it expects after birth.
In simpler terms, the smell of fatty foods during pregnancy acts like a signal to the developing baby. Even if the mother eats healthy food, her exposure to fatty-food odors tells the developing brain of her unborn child that high-fat food is abundant. The brain then adapts its hunger and reward circuits to prepare the body to store more fat later.
Hence, once born and when the child further grows up and eats a high-fat diet, they gain weight more easily and are more likely to develop obesity or metabolic problems. This essentially shows that the exposure to odor molecules from food programs the metabolism of an individual before birth, thereby influencing how they react to food in the future.
The effect required ingestion of the odor-producing foods. Passive exposure did not produce the effect. The obesity predisposition appeared only when the offspring were later exposed to a high-fat diet. Moreover, while mice are established models for metabolism programming, the results and underlying mechanisms may not directly translate to humans.
FURTHER READING AND REFERENCE
- Casanueva Reimon, L., Gouveia, A., Carvalho, A., Schmehr, J. N., El Mehdi, M., Moreira-Soto, R. D., Ardanaz, C. G., Bulk, J., Rigoux, L., Klemm, P., Cremer, A. L., Dethloff, F., Hinze, Y., Backes, H., Giavalisco, P., and Steculorum, S. M. (2025). “Fat Sensory Cues in Early Life Program Central Response to Food and Obesity.” Nature Metabolism. DOI: 1038/s42255-025-01405-8