TOPLINE

Children with obesity at ages of 4, 6, or 8 years were strongly likely to still have obesity at the age of 13 years, whereas those with only overweight at the same ages had a much lower chance of progressing to obesity — even if their BMI had recently risen from normal weight.

METHODOLOGY

• Researchers conducted a retrospective population-based study using routine child health records from two large Norwegian municipalities to examine BMI changes during childhood and their association with obesity at the age of 13 years.
• A total of 124,470 children were analysed, contributing to 360,957 observations of height and weight at ages of 2, 4, 6, 8, and 13 years between 1991 and 2017.
• BMI categories — normal weight (including underweight), overweight, and obesity — were defined using International Obesity Task Force age- and sex-specific cutoffs, which linked childhood BMI values to equivalent adult BMI thresholds.
• Children were additionally classified by visit type as those with routine visits only and those with additional visits, which often reflected closer follow-up because of their higher BMI.

TAKEAWAY

• Children classified as having a normal weight at ages of 2, 4, 6, or 8 years had a low predicted probability of obesity at the age of 13 years (0.4%-2.0%). Overweight at those same ages carried a substantially higher, but still modest, probability (8%-10%). Obesity at ages of 4, 6, or 8 years, by contrast, was strongly associated with obesity at the age of 13 years, with predicted probabilities rising from 38% if obesity was present at the age of 4 years to 41% if obesity was present at the age of 6 years and 51% if obesity was present at the age of 8 years.
• Prior transitions between BMI categories had a minimal influence on a later risk for obesity; among children with overweight at the age of 6 years, the associated risk for obesity at the age of 13 years remained narrow at 9%-12%, regardless of whether they had normal weight or overweight at the age of 4 years.
• Among children with obesity at the age of 8 years, the associated risk for obesity at the age of 13 years ranged from 36% to 55%, depending on BMI status at the age of 6 years.
• Children who received additional follow-up had higher BMI levels, were less likely to return to normal weight, and more often had obesity at the age of 13 years than those who attended routine visits. However, only about 20% of children with overweight and 40% of those with obesity at the age of 13 years had received additional follow-up, despite national guidance recommending follow-up to all children in these groups.

IN PRACTICE

"[The study] findings emphasize the importance of combining targeted clinical care with population-level prevention," the authors wrote.

SOURCE

This study was led by R. Ødegård, Obesity Research Centre, St. Olavs Hospital HF, Trondheim University Hospital, Trondheim, Norway. It was published online on August 21, 2026, in Acta Paediatrica.

LIMITATIONS

Individual-level data on healthcare contacts beyond school health services were unavailable. The study lacked data on family, socioeconomic, and lifestyle factors known to influence weight trajectories. Generalisability to populations with higher baseline obesity prevalence, different healthcare services, or different prevention strategies may be limited.

DISCLOSURES

No specific funding was reported. The authors declared having no relevant conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.