Socioeconomic gradients in body weight of German children reverse direction between the ages of 2 and 6 years

In Western societies, there is an inverse socioeconomic status (SES) gradient in overweight, but its onset is unknown. It was the aim of this study to assess the onset of the SES gradient in overweight children from birth to age 5-7 y. This was a cross-sectional and longitudinal study of 1326 children [668 boys and 658 girls; median age, 6.3 y; interquartile range (IQR), 0.4 y] in Kiel, northwest Germany. We assessed parental education as an indicator of SES, parental body mass index (BMI) (fathers: median age, 37.0 y; IQR: 8.0 y; mothers: median age, 34.0 y; IQR, 6.5 y), BMI of mothers before pregnancy, and breastfeeding practices. We found a positive SES gradient in birthweight, which was further enhanced by parental overweight. SES gradients in nutritional status disappeared at the age of 1 and 2 y. In contrast, in 5- to 7-y-old children, there was an inverse SES gradient in BIVII and overweight, which was further enhanced by parental overweight. We concluded that (i) SES gradients in nutritional state show considerable changes during the first years of life, (ii) the inverse SES gradient in overweight becomes manifest between years 2 and 6 of life and (iii) parental BIVII enhances SES gradients in birthweight and BIVII at 5-7 y of age.