Abstract The adiposity peak (AP) and adiposity rebound (AR) are the highest and lowest points of the body mass index (BMI) growth trajectory in early life. They are also the most significant characteristics. Epidemiological studies have reported the timings and BMI magnitudes of AP and AR in different populations worldwide. Others have observed the impacts of prenatal, postpartum, feeding, economic and social factors on the timing and magnitude of them. In addition, longitudinal studies have tracked the health effect of the timing and magnitude of them on many adverse health outcomes in later life. Based on literature reviews, we summarize the global epidemiological characteristics of AP and AR, while identifying pre and early life determinants as well as their possible long term health effects, so as to provide scientific evidence for the prevention and management of obesity and related chronic diseases. We also highlight current controversies regarding this issue, while outlining directions for future research.

Objective: To explore the effect of breastfeeding duration on age at adiposity rebound, and provide a scientific theoretical basis for identifying early life factors of obesity in children and adolescents, while promoting early intervention. Methods: In September 2019, first graders from a primary school in Minhang District, Shanghai, were selected to participate in this study, and their growth information was retrospectively collected. The natural cubic spline function was used to fit the body mass index trajectory of the subjects from 1 to 80 months, and age at adiposity rebound was calculated. A total of 6 148 subjects were selected, and complete data of adiposity rebound timing and breastfeeding duration were obtained. A multiple linear regression model was used to analyze the relationship between these two variables. Results: The average breastfeeding duration of all children included in the study was (3.71±3.28) months, and most of the subjects (69.63% for male and 70.45% for female) were breastfed for less than 4 months. A positive linear relationship was found between them [male, B =0.16(0.02-0.30), female, B =0.34(0.18- 0.51 ), total, B =0.23(0.12-0.34), P <0.05]. The linear relationship was determined using the multivariate model. Conclusion Breastfeeding duration independently affected age at adiposity rebound. Prolonging the duration of breastfeeding within 24 months of age may help to delay the timing of adiposity rebound,and thus reduce later risks of overweight and obesity.

Objective: To explore the influence of birth weight and growth patterns during infancy on overweight and obesity among first grade primary school pupils, so as to provide a theoretical basis for the formulation of early life prevention and intervention policies. Methods: In 2019, data related to routine physical examinations were collected for primary school pupils in the Minhang District of Shanghai, and information regarding birth and follow ups was collected retrospectively. Physical examination data of 4 434 pupils at 12 months of age were obtained. A multiple linear regression model was used to analyze the relationship between growth patterns during infancy and body mass index (BMI) in the first grade of primary school. A generalized linear model was employed to analyze the relationship between birth weight and growth patterns during infancy and overweight and obesity in the first grade of primary school. A hierarchical analysis was conducted. Results: A linear relationship was observed between growth patterns during infancy and BMI and the BMI Z score of first grade primary school pupils [ β(β 95%CI)=0.30(0.24-0.35),0.12(0.10- 0.15 ), P <0.01]. In addition to subjects classified as small for gestational age (SGA), catch up growth during infancy was identified among subjects who were classified as appropriate for gestational age (AGA) and large for gestational age (LGA). LGA at birth and catch up growth during infancy were independent risk factors for overweight and obesity among first grade primary school children ( RR =1.31-1.55, P <0.05). The hierarchical analysis showed that catch up growth increased the risk of overweight and obesity among first grade primary school pupils classified as AGA [ RR(RR 95%CI )=1.74(1.42-2.14),1.87(1.56-2.26)], and increased the risk of obesity among first grade primary school pupils classified as SGA and LGA [ RR(RR 95%CI )=3.74(1.04-13.49),3.24(1.62-6.46)]( P <0.05). Among those who exhibited catch up growth during infancy, LGA increased the risk of obesity among first grade primary school pupils ( RR= 2.60 , 95%CI=1.35-5.02, P <0.01), but not the risk of being overweight ( P =0.13). Conclusion Birth weight and growth patterns during infancy have an impact on overweight and obesity among children in the first grade of primary school. It is suggested that attention should be paid to growth and physical development in early life for those classified as LGA and AGA, and catch up growth in children should be closely monitored.

Objective: To explore the characteristics of the adiposity peak and rebound in early life among first year primary school students with different body weight measures, so as to provide scientific evidence for the development of prevention interventions to manage childhood overweight and obesity. Methods: A total of 2 330 first year primary school students who received routine physical examinations from September to December in 2019 were selected. According to body mass index (BMI) status, participants were divided into three categories:healthy weight, overweight, and obese. The BMI growth trajectories of the three groups were fitted by gender using the generalized additive mixed model from 1 to 80 months, retrospectively. Each subject s age at the adiposity peak and rebound, and associated BMI values, were calculated. Results: The prevalence of overweight and obesity was 16.31 % (380/ 2 330 ) and 16.09% (375/2 330), respectively. For first year students with obesity, the BMI value continued to be higher than their overweight or healthy weight counterparts during the first 80 months of life. The age at the adiposity peak for these students, whose BMI status varied, was about nine months. However, the BMI of children with overweight or obesity was much higher than that of healthy weight subjects. Age at adiposity rebound was 72 months for healthy weight children, 52 to 55 months in children defined as overweight, and 22 to 23 months in children with obesity. For healthy weight children, the fitted value of BMI at the adiposity rebound was less than that of overweight and obese children. Conclusion Age at the adiposity peak was largely similar among first year students with different BMI patterns; however, age at adiposity rebound was different. Age at adiposity rebound among children with obesity was much earlier than that of other subjects, and their BMI values were much higher.