Smelling Fatty Foods in Womb May Raise Obesity Risk

Pregnancy is a critical window during which signals from the environment can shape a baby’s long-term health (1^✔ ✔Trusted Source
Fat sensory cues in early life program central response to food and obesity

Go to source). A new study published in the journal Nature Metabolism has found that not only what a mother eats, but also what she smells during pregnancy, may influence her offspring’s future risk of obesity and metabolic disease.

How the Study Tested Fatty Food Smells in Pregnancy

In this study, pregnant mice were divided into two main groups. Both groups received the same nutritionally balanced, low-fat chow. For the experimental group, the chow was specially flavored with a strong fatty food odor similar to processed high-fat foods, while the control group received chow without this added odor. The calorie content and nutrients were kept identical.

Throughout pregnancy and breastfeeding, the mothers in both groups showed similar weight gain and normal metabolic health. Blood sugar levels, body weight, and milk composition were comparable. Fetal weights and early postnatal growth were also similar, which means the odor exposure itself did not cause obvious growth problems.

The real differences appeared later. After weaning, all offspring were switched to a high-fat diet. Mice that had been exposed to the fatty food odor before birth and via milk developed significantly more body fat, reduced energy expenditure, and insulin resistance when compared with unexposed controls. These features are characteristic of an increased risk of obesity and type 2 diabetes in later life.

Brain Circuits for Hunger and Reward Rewired

To understand what caused these long-term changes, researchers examined the brains of the adult offspring. They focused on regions that control appetite, reward, and energy balance.

They found that key reward pathways involving dopamine were altered in the odor-exposed mice. These circuits normally help regulate how rewarding foods feel and how strongly animals seek them out. Changes in these pathways can make high-fat foods more compelling and harder to resist.

In addition, neurons that produce Agouti-related peptide (AgRP), which act as powerful hunger signals, showed abnormal responses. Typically, high-fat feeding reduces AgRP neuron activity to limit further intake (2^✔ ✔Trusted Source
Fatty food smells during pregnancy may raise obesity risk in offspring

Go to source).

In odor-exposed animals, this response was blunted. The brain behaved as if it were less satisfied by fatty food, potentially encouraging overeating or conserving energy. These neural changes persisted into adulthood, indicating a form of metabolic programming.

Smell as a Hidden Prenatal Programming Signal

The findings suggest that volatile scent molecules from fatty foods can reach the fetus via amniotic fluid and later via breast milk. These odor cues appear to act as early-life signals that help the developing brain predict the kind of food environment it will face after birth.

If the brain expects a high-fat environment, it may program metabolism to efficiently store energy and respond strongly to fatty foods. In modern settings, where calorie-dense foods are easily available, such programming could increase the risk of obesity and related metabolic disorders.

The research was done in mice, so it cannot be directly applied to humans yet. However, it raises important questions about how everyday food smells during pregnancy and breastfeeding might influence long-term weight and metabolic health in children.

Final Takeaway

The study in Nature Metabolism provides evidence that early exposure to fatty food odors can reprogram brain circuits for hunger and reward, predisposing offspring to greater fat gain and insulin resistance when they encounter rich diets later in life.

While human studies are needed, the work suggests that a healthy prenatal environment may include not only what mothers eat, but also the kinds of food smells they are regularly exposed to during pregnancy.

References:

1. Fat sensory cues in early life program central response to food and obesity - (https://www.nature.com/articles/s42255-025-01405-8)
2. Fatty food smells during pregnancy may raise obesity risk in offspring - (https://medicalxpress.com/news/2025-12-fatty-food-pregnancy-obesity-offspring.html)

Source-Medindia