At age 3, half of what Dutch toddlers ate by weight was ultra-processed. The heaviest eaters gained more by age 11

Most of the evidence tying ultra-processed food (UPF) to weight gain comes from adults. A study published in BMC Medicine on 28 September 2026 looked at children in two Dutch cohorts: 1,091 children from GECKO Drenthe whose diet was recorded at age 3, and 2,970 children from Lifelines whose diet was recorded at ages 8 to 12. Foods were sorted with the NOVA system, and trained nurses later measured height and weight.

UPF made up a large share of what these children ate: a median of 744 g a day at age 3, 52% of their food by weight, and 908 g a day at ages 8 to 12, 50% of intake. In the toddler cohort, children in the top quarter of UPF intake had a bigger rise in BMI z-score (BMI adjusted for age and sex) between ages 3 and 10 or 11 than those in the bottom quarter. A cross-lagged analysis suggested the direction ran from early UPF intake to later BMI, not the other way round.

In the older cohort the result went the other way: higher UPF at 8 to 12 was linked with slightly lower BMI z-scores at 9 to 17. The authors say this evidence was less consistent, and older children who are already heavier may be steered away from snacks, which can reverse an association. Their conclusion is that early childhood may be a sensitive period for UPF and weight gain. Food questionnaires filled in by parents are rough measures, so the numbers are a guide, not a precise count.