Published today in Nature Communications, a new study by researchers at University College Cork (UCC) has found that eating unhealthy foods early in life can lead to long-lasting changes in the brain and eating habits — but that helpful gut bacteria might be able to undo some of these effects.
The researchers found that eating a diet high in fat and sugar during early life changed how the brain controls eating, even after returning to a normal diet and normal body weight later on. These changes were not just short-lived; they lasted into adulthood in their experimental model.
Children today grow up in environments where high-fat, high-sugar foods are everywhere. These foods are easy to access and are often encouraged. They appear at birthday parties, school events, sports games, and even as treats for good behaviour. As a result, these unhealthy foods have become a normal part of many children’s lives.
The new research shows that this early and frequent exposure to unhealthy, energy-dense, nutrient-poor foods can influence food preferences and lead to unhealthy eating habits that last into adult life. In other words, what children eat when they are young can shape their eating behaviour for years.
The team behind the research used a mouse model for their study. They fed young mice a diet high in fat and sugar and then studied them when they reached adulthood. Even after the unhealthy diet was stopped and the mice returned to a normal body weight later in life, the researchers still observed changes in the brain and in how the animals ate.
The scientists discovered that these long-lasting changes were connected to a part of the brain called the hypothalamus. The hypothalamus plays an important role in controlling appetite and managing energy balance. When its normal function is disrupted, it can lead to changes in hunger signals and eating behaviour.
One of the main authors of the study, Dr Cristina Cuesta-Martí, said, “Our findings show that what we eat early in life really matters. Early dietary exposure may leave hidden, long-term effects on feeding behaviour that are not immediately visible through weight alone.”
This means that even if a child appears healthy and has a normal weight, their early diet could still have altered the brain in ways that affect eating behaviour later in life.
The research also suggests that these changes could raise the risk of obesity later in life. Because early unhealthy eating alters brain pathways linked to feeding, it can make it harder for a person to make healthy food choices or control how much they eat as they grow older.
The study also revealed some positive findings. It showed that supporting the gut microbiome — the bacteria and microbes in the digestive system — can lessen the long-term effects of early unhealthy eating.
Researchers tested two ways to support gut health. One was a probiotic called Bifidobacterium longum APC1472. The other was a mixture of prebiotic fibres, FOS and GOS.
Prebiotics such as fructo-oligosaccharides (FOS) and galacto-oligosaccharides (GOS) are found naturally in foods including onions, garlic, leeks, asparagus, and bananas. They are also added to some fortified foods and supplements. These fibres are known to support beneficial gut bacteria.
When the mice received the probiotic strain Bifidobacterium longum APC1472, the researchers observed noticeable improvements in feeding behaviour. Interestingly, this probiotic caused only small changes in the overall composition of gut bacteria, suggesting it acted in a targeted way. In contrast, the prebiotic mixture of FOS and GOS changed the gut microbiome more broadly.
Dr Harriet Schellekens, the lead researcher, said that supporting the gut microbiome from birth can reduce the negative effects of an unhealthy early diet on later eating habits. Strengthening gut health early may help protect the brain from diet-related changes.
Professor John F. Cryan of UCC added that the study demonstrates how basic science can address real-world problems. Early eating habits shape brain areas that control food choices and may also influence future microbiome-based treatments.
The study was led by UCC, with partners from the University of Seville, the University of Gothenburg, and the Teagasc Food Research Centre. Funding was provided by Research Ireland, a Government of Ireland scholarship, and a Biostime Institute award.
