OBJECTIVE: The literature on associations between fat intake and weight development among both children and adults is inconsistent, even if it is generally assumed that a high dietary fat intake is a major determinant of obesity. The present study aimed at investigating the association between fat intake and weight development among a cohort of children aged 9-10 years at baseline and 15-16 years at follow-up, and, further, at investigating whether parents' obesity is modifying the association. METHOD: Among 384 subjects aged 9 years, data on dietary intake, BMI z-score, physical activity, inactivity, parents' social status, parents' body mass index, child birth weight, and status of puberty was obtained in 1997. Weight and height was measured both at baseline and at 6-year follow-up, and BMI z-score was calculated. Linear regression was used to assess the role of fat intake on subsequent weight change between 1997 and 2003 with the above-mentioned variables as confounders, in 3 different models and for each sex separately. RESULTS: The analysis showed no relation between fat intake (both absolute intake and fat energy percent) at 9 years and subsequent 6-year weight change. Only BMI z-score at baseline had a significant relation to weight change for both sexes, and number of obese parents had significant relation to weight change in girls. Number of overweight parents did not modify the association between fat intake and weight change. CONCLUSION: This study was unable to find a relation between fat intake and 6-year weight change among 9-year-old children. No interaction was seen between number of overweight parents on the relation between fat intake and subsequent weight change.