Early-life Exposure to Fat-related Food Odours May Shape Lifelong Obesity Risk
Key Takeaways:
- Early exposure to fat-related food odours during development may prime the brain and body for heightened metabolic responses to high-fat foods later in life.
- Sensory cues from a maternal diet, independent of nutritional content or maternal metabolic status, can influence thermogenesis, gene expression, and susceptibility to obesity in adult mice.
- Findings suggest a previously underappreciated mechanism of metabolic programming, in which food odours encountered during gestation and lactation can affect lifelong dietary preferences and obesity risk.
Introduction
A recent study published in Nature Metabolism explores how non-nutritive sensory cues from foods rich in fat, particularly odours, influence the developing brain and metabolic pathways. The research investigates how these early sensory inputs may shape central responses to food cues, metabolic health, and the risk of obesity in adulthood. The findings expand on a substantial body of work showing that early-life nutritional exposure influences later metabolic outcomes, but highlight the specific and previously overlooked contribution of fat-related odours.
Maternal obesity and early nutritional exposure
How maternal diet affects offspring
Developmental exposure to a maternal diet high in calories and fat is a well-recognised risk factor for obesity and metabolic disorders throughout life. Numerous studies have linked maternal high-fat diet (HFD) consumption with outcomes such as excess gestational weight gain, insulin resistance, and increased adiposity in mothers, all of which may contribute to lifelong metabolic vulnerability in offspring.
Despite these strong associations, the specific components of HFDs that drive metabolic programming remain only partly understood. While nutrients themselves contribute directly to energy balance and metabolic pathways, foods also contain non-nutritive sensory elements, including volatile odours. Fetuses and newborns experience these odours during development, meaning that sensory exposure is layered on top of nutritional exposure.
Sensory memories formed early in life
Perinatal olfactory experiences contribute to the formation of sensory memories that influence food preferences and eating habits into adulthood. The authors emphasise that understanding how non-nutritive cues from a maternal HFD influence long-term dietary preferences and metabolic responses is crucial for clarifying early-life drivers of obesity risk.
Study approach
Separating nutritional and sensory influences
To distinguish nutritional caloric components from sensory components, the researchers designed an isonutritional model using a standard normal chow diet (NCD) infused with fat-related odours. This bacon-flavoured diet (BFD) enabled researchers to expose mice to fat-related sensory cues without increasing calorie content.
- BFD: NCD enriched with bacon odours, designed to mimic the odour profile of a standard lard-based high-fat diet (HFDlard).
- HFDbutter: A butter fat-based HFD used to represent a non-pork, high-fat option.
This design allowed the researchers to isolate the effect of fat-related sensory exposure during development, independent of maternal metabolic changes such as insulin resistance, weight gain, or altered lipid levels.
Odour profile analysis
A detailed chemical characterisation identified 155 volatile compounds across the diets, including aldehydes, ketones, and alcohols. Hierarchical clustering revealed:
- HFD and HFDlard shared high sensory similarity
- Both differed significantly from HFDbutter and NCD
- BFD’s odour profile closely matched HFDlard, yet its nutritional profile remained identical to NCD
These findings confirmed that BFD was an appropriate tool for studying sensory-specific metabolic programming.
Sensory cues and neural activation
Experimental analyses showed that fat-related food odours induced phosphorylation of S6 in olfactory sensory neurons (OSNs), demonstrating that the odours elicited detectable neural activation. Mice perceived BFD as more similar to HFDlard than to NCD, reinforcing that the sensory model accurately represented fat-related olfactory cues.
Early exposure and adult metabolism
Developmental exposure primes obesogenic responses
Control mice exposed only to NCD during development (NCDdev) showed no changes in interscapular brown adipose tissue (iBAT) thermogenesis or hepatic mechanistic target of rapamycin (mTOR) phosphorylation when later exposed to HFDlard odours. In contrast, mice developmentally exposed to BFD (BFDdev) displayed significant increases in both iBAT temperature and hepatic p-mTOR when encountering these odours for the first time in adulthood.
This indicates that early exposure to fat-related odours enhances metabolic responsiveness to high-fat sensory cues later in life.
Independent of maternal obesity
Importantly, these heightened responses occurred without maternal insulin resistance, adiposity, or weight gain. This demonstrates that sensory exposure alone, rather than changes in maternal metabolism, can programme obesity risk.
Sex-specific sensitivity
- Females: Lactation appeared to be the most sensitive developmental window for programming effects.
- Males: Required exposure throughout the entire developmental period to exhibit similar heightened metabolic responses.
Responses to different high-fat diets
Eight-week-old BFDdev and NCDdev mice were also exposed to HFDbutter. The aim was to test whether heightened susceptibility required precise sensory matching or whether vulnerability generalised across high-fat diets.
Findings showed that early exposure to fat-related sensory cues increased obesity susceptibility even when adult exposure involved a high-fat diet with different sensory characteristics. This suggests that early sensory programming affects broad metabolic pathways rather than specific flavour-diet associations.
While a perfect sensory match between early and later exposure was not necessary, some degree of sensory similarity still appeared relevant in shaping metabolic outcomes.
Changes in the maternal environment
The study found that feeding mothers BFD altered the volatile odour profile of both amniotic fluid and milk. These changes exposed developing offspring to fat-related sensory information during gestation and lactation, influencing their early sensory learning and shaping later responses to food.
Impairments in thermogenesis and metabolic flexibility
BFDdev mice demonstrated reduced iBAT thermogenesis compared with NCDdev controls. They also exhibited lower expression of thermogenic-related genes in iBAT, including:
- Cidea
- Pparg
These findings indicate that developmental exposure to fat-related odours impairs metabolic flexibility and weakens homeostatic responses to hypercaloric diets in adulthood.
Altered neuronal responses to fat
The researchers reported a specific impairment in Agouti-related peptide (AgRP) neuronal responsiveness to dietary fat in BFDdev mice. These neurons help regulate hunger and energy balance. Despite this, responses to major hormonal signals remained unaffected, suggesting that sensory-specific pathways were selectively disrupted.
Conclusion
The study provides compelling evidence that early-life exposure to fat-related food odours can contribute to long-term obesity risk by shaping metabolic and neuronal responses long before an individual consumes high-fat foods. These sensory cues act independently of calorie exposure and maternal metabolic health, highlighting a novel pathway through which obesity susceptibility may be programmed. Although the research was conducted in mice, it underscores the potential importance of early sensory environments in influencing metabolic health across the lifespan.
CCH insights:
This is fascinating research. We already know that the diet of a pregnant woman can influence the dietary preferences and health outcomes of her child, but now it appears odours of certain foods during pregnancy may have similar affects. It adds an intriguing new line of investigation in terms of the Developmental Origins of Health and Disease. However, we must remember this study was in mice, using bacon odours to mimic a lard-based high fat diet, so we are a long way from being able to draw conclusions about real world implications for pregnant women.
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