Scientists also explored whether improving gut health could help reduce some of these effects.

Children regularly exposed to junk food packed with sugar and fat may carry hidden effects into adulthood, with new research suggesting unhealthy eating early in life could leave lasting effects on how the brain regulates food habits.

The study, published in Nature Communications, found that long after diets improve and body weight returns to normal, changes linked to appetite and feeding behaviour may continue to persist.

Researchers at APC Microbiome Ireland at University College Cork examined how calorie-dense, nutrient-poor diets affected the body during early development. Using a preclinical mouse model, scientists observed that animals given high-fat and high-sugar diets early in life later showed altered eating behaviour as adults.

The findings linked these long-term changes to disruptions in the hypothalamus, the part of the brain responsible for regulating hunger and maintaining energy balance.

Scientists also explored whether improving gut health could help reduce some of these effects. Researchers tested a probiotic bacterial strain, Bifidobacterium longum APC1472, along with prebiotic fibres known as fructo-oligosaccharides and galacto-oligosaccharides.

These fibres naturally occur in foods such as onions, garlic, bananas, leeks and asparagus and are also found in some fortified foods and supplements.

Researchers said constant exposure to processed foods during childhood may shape food preferences early, while findings suggested gut bacteria-based interventions could help support healthier eating patterns later in life.