The research team set out to address a persistent gap in nutritional science. While numerous studies in adults have connected ultra-processed food intake with overweight and obesity, robust longitudinal evidence in children and adolescents has remained limited. Most existing pediatric studies rely on short follow-up periods or single measurements, making it difficult to establish whether diet drives weight change or whether body weight shapes dietary behavior. The Dutch researchers designed their analysis to capture the dynamic relationship between diet and growth over the crucial transition from early childhood into adolescence, using repeated measurements of height and weight collected by trained nurses rather than self-reported values.

The study drew on two complementary Dutch cohorts. The first, GECKO Drenthe, is a birth cohort coordinated through the Groningen Expert Center for Kids with Obesity, in which 1,091 children, evenly split between boys and girls, had their diets assessed at age three using a validated food frequency questionnaire completed with parental assistance. The second, Lifelines, is a large population-based cohort in which 2,970 children aged eight to twelve, half of them male, provided dietary information through the same validated instrument. In both cohorts, food items were categorized according to the NOVA classification system, the most widely used framework for distinguishing ultra-processed products, which are industrial formulations typically made from refined substances and additives with little resemblance to whole foods.

The scale of ultra-processed food consumption among these Dutch children was striking. In the GECKO cohort, the median intake at age three was 744 grams per day, accounting for roughly 52 percent of total food intake by weight. In Lifelines, children aged eight to twelve consumed a median of 908 grams per day, representing about half of everything they ate. These figures mean that the average Dutch child in these cohorts obtained the majority of their daily food, by weight, from industrially manufactured products, a pattern consistent with broader trends across high-income countries where ultra-processed items dominate children’s diets.

The central finding emerged from the younger cohort. In GECKO Drenthe, children in the highest quartile of ultra-processed food consumption at age three showed a significantly greater increase in their age- and sex-standardized body mass index, known as BMI z-score, between age three and age ten or eleven compared with children in the lowest quartile. The regression coefficient was 0.22, with a 95 percent confidence interval of 0.07 to 0.37, indicating a statistically robust association. BMI z-scores are a standard pediatric metric that expresses a child’s body mass index relative to peers of the same age and sex, allowing researchers to track whether a child’s weight trajectory is drifting upward relative to the population norm over time.

Perhaps the most intriguing result, however, came from the cross-lagged panel models, a statistical technique designed to probe the temporal direction of relationships between variables measured at multiple time points. In the GECKO cohort, these analyses indicated a directional association in which early ultra-processed food intake predicted later BMI z-score, rather than the reverse. This is a critical distinction in observational nutrition research, because heavier children are sometimes assumed to simply eat more of everything, including processed products. The cross-lagged evidence suggests that, at least in early childhood, the arrow of causality points from diet to weight, with high ultra-processed food consumption preceding and predicting subsequent weight gain rather than resulting from it.

The picture in older children was more complicated. In the Lifelines cohort, higher ultra-processed food intake at ages eight to twelve was actually associated with lower BMI z-scores measured between ages nine and seventeen. Compared with children in the lowest consumption quartile, those in the second quartile had a coefficient of minus 0.12, those in the third quartile minus 0.20, and those in the highest quartile minus 0.13, all with confidence intervals excluding zero. The authors themselves characterize this inverse association as less consistent, and they caution against interpreting it as evidence that ultra-processed foods protect against weight gain in adolescence. Reverse causation, residual confounding by socioeconomic status or physical activity, and the coarser dietary assessment possible in older children may all contribute to the unexpected pattern.

Several biological and behavioral mechanisms could explain why early childhood appears especially vulnerable to the effects of ultra-processed foods. During the first years of life, the body undergoes rapid growth and metabolic programming, and adiposity trajectories established in this period tend to track into later childhood and adulthood. Ultra-processed products are typically energy-dense, high in added sugars, refined starches and unhealthy fats, and low in fiber and micronutrients, a combination that can promote passive overconsumption because they are palatable, convenient and often marketed in large portions. Early exposure may also shape taste preferences and eating behaviors that persist for years, embedding a dietary pattern that continuously favors excess energy intake. The developing hypothalamic regulation of appetite and satiety may likewise be influenced by the nutrient profile of the early diet, though the authors emphasize that further longitudinal research across developmental stages is needed to confirm these pathways.

The study’s strengths lie in its prospective design, its use of two independent cohorts, objectively measured height and weight collected by trained nurses, and a validated food frequency questionnaire applied consistently across age groups. Standardized BMI z-scores and the International Obesity Task Force criteria for overweight and obesity provided internationally comparable endpoints. Nevertheless, the researchers acknowledge limitations inherent to observational nutrition studies. Food frequency questionnaires depend on parental reporting for young children and self-report for older ones, both of which are subject to measurement error and social desirability bias. The NOVA classification, while influential, groups heterogeneous products together, and residual confounding by family socioeconomic circumstances, physical activity and other dietary components cannot be fully excluded. The inverse association observed in Lifelines in particular underscores the need for caution before drawing firm conclusions about adolescents.

The implications for public health are nonetheless significant. If early childhood is indeed a sensitive period for the obesogenic effects of ultra-processed foods, interventions aimed at reducing these products in toddler and preschool diets could yield disproportionate long-term benefits, potentially preventing the upward drift in body mass index that foreshadows adolescent and adult obesity. The findings add momentum to international efforts, including front-of-pack labeling schemes, marketing restrictions targeting young children and dietary guidelines that explicitly recommend limiting ultra-processed products. As ultra-processed foods continue to expand into low- and middle-income countries, understanding which developmental windows matter most will be essential for designing effective prevention strategies. This Dutch study provides some of the strongest longitudinal evidence yet that the earliest years of life may be exactly when dietary quality matters most for lifelong weight trajectories.

Subject of Research: Longitudinal associations between ultra-processed food consumption and body mass index development from childhood to adolescence

Article Title: Ultra-processed food consumption and body mass index development from childhood to adolescence in Dutch cohorts

Article References: Yang, J., Navis, G., & Corpeleijn, E. (2026). Ultra-processed food consumption and body mass index development from childhood to adolescence in Dutch cohorts. BMC Medicine. https://doi.org/10.1186/s12916-026-05270-4

Image Credits: AI Generated

DOI: 10.1186/s12916-026-05270-4

Keywords: ultra-processed foods, childhood obesity, BMI z-score, NOVA classification, GECKO Drenthe cohort, Lifelines cohort, pediatric nutrition, longitudinal study, weight gain, cross-lagged analysis, public health, Netherlands