The dynamics of body-mass index (BMI) in children from birth to adolescence are unclear, and whether susceptibility for the development of sustained obesity occurs at a specific age in children is important to determine.

The familial social background of a child can significantly impact their behavior and health. We investigated associations between socio-economic status (SES) and health parameters and behaviors in German children and adolescents. Data were collected between 2011 and 2018 in the framework of the LIFE Child study. Participants included 2998 children aged 3–18 years. SES was represented by an index combining information on parental education, occupation, and income. Associations between SES and health outcomes were estimated using linear and logistic regression analyses. In a moderator analysis, all associations were checked for interactions between SES and age or sex. A higher SES composite score was associated with better health (lower body mass index (β = −0.26), fewer behavioral difficulties (β = −0.18), higher quality of life (β = 0.21), fewer critical life events (odds ratio (OR) = 0.93); all p < 0.05) and a healthier lifestyle (healthier nutrition (β = 0.16), less excessive television use (OR = 0.87), less nicotine consumption (OR = 0.93), and more physical activity (OR = 1.18); all p < 0.05). However, SES was not associated with alcohol consumption (OR = 1.02) or sleep problems (β = −0.04). The strengths of the associations between SES and child health did not differ depending on SES indicator (education, occupation, income). The associations between SES and parent-reported behavioral difficulties and physical activity were stronger in older vs. younger children. In contrast, none of the observed associations were moderated by sex. This study highlights the strong association between socio-economic status and child health, even in modern Western societies.

Background/Objectives: There is a concern that measures aiming to limit a further spread of COVID-19, e.g., school closures and social distancing, cause an aggravation of the childhood obesity epidemic. Therefore, we compared BMI trends during the 15 years before and during the COVID-19 pandemic.Subjects/Methods: To assess the change in weight dynamics during the first months of COVID-19, we compared the trends of 3-month change in BMI-SDS (ΔBMI-SDS) and the proportions of children showing a high positive (HPC) or high negative (HNC) weight change between 2005 and 2019 and the respective changes from 2019 (pre-pandemic) to 2020 (after the onset of anti-pandemic measures) in more than 150,000 children (9689 during the pandemic period). The period of 3 months corresponds approximately to the first lockdown period in Germany.Results: During the COVID-19 pandemic, we found a substantial weight gain across all weight and age groups, reflected by an increase in the 3-month change in BMI-SDS (β = 0.05,p < 0.001), an increase in the proportion of children showing HPC (OR = 1.4,p < 0.001), and a decrease in the proportion of children showing HNC (OR = 0.7,p < 0.001). Besides, we found the same trends since 2005 on a low but stable level with a yearly increase of ΔBMI-SDS byβ = 0.001 (p < 0.001), the odds of HPC increased by OR_{high_pos} = 1.01 (p < 0.001), and the odds of HNC decreased by OR_{high_neg} = 0.99 (p < 0.001). These rather small effects accumulated toβ = 0.02, OR_{high_pos} = 1.14, and OR_{high_pos} = 0.85 over the whole period 2005–2019. Alarmingly, both the long-term and the short-term effects were most pronounced in the obese subgroup.Conclusions: There are positive dynamics in different measures of weight change, indicating a positive trend in weight gain patterns, especially within the group of children with obesity. These dynamics are likely to be escalated by COVID-19-related measures. Thus, they may lead to a significant further aggravation of the childhood obesity pandemic.