Retrospective tracking of young obese children back to birth in Japan: special attention to the relationship with parental obesity.

OBJECTIVE: Childhood obesity is tracked to adulthood at a high rate. However, longitudinal studies of obesity in early childhood remain limited. This study aimed at tracking young obese children back to birth in comparison with normal-weight children, and investigating the relationship with parental obesity. METHODS: A total of 2,678 (1,353 boys) young children attending kindergarten or nursery school in Nara Prefecture, Japan, were enrolled. The present heights and weights of children and parents were obtained by a questionnaire, and children's heights and weights at birth, 1.5, and 3.5 years were obtained from mother-child health notebooks. Using body mass index (BMI), child and parental obesity were defined as >=90th percentile based on the reference values for Japanese children and >=25 (kg/m²), respectively. RESULTS: The overall prevalence of obesity at birth was 10.2%, and decreased to 5.6% at 5 years. In the retrospective tracking, obese children at 5 years exhibited significantly higher weight Z-scores and BMI percentiles consistently from birth than in normal-weight children. The increased velocity of weight gain as judged by their Z-score during three periods; birth-1.5, 1.5-3.5, and 3.5-5 years were significantly associated with an increased risk for the obesity at 5 years of age. Only maternal obesity was found to be associated with daughters' obesity in the analysis of association of parents-children obesity. CONCLUSIONS: It is important to manage body weight from early infancy for reducing the occurrence of obesity at 5 years. Where there is maternal obesity, greater attention may be required, especially for daughters.

Longitudinal study of thinness from birth to early childhood: the association with parental thinness.

AIM: Epidemiological research on thinness, particularly in early childhood, is limited. This study tracked thin children aged 5 years back to birth, compared them with normal-weight children and investigated the relationship with parental thinness. METHODS: We enrolled 2678 children (50.5% boys) aged 5 years and attending kindergarten or nursery in the Nara Prefecture of Japan. The children's height and weight at birth, 1.5 years and 3.5 years, were obtained from mother-child health records. Child thinness was defined as having a body mass index (BMI) of less than the fifth percentile of the reference values for Japanese children, and parental thinness was defined as a BMI of <18.5. RESULTS: The overall prevalence of thinness at 5 years of age was 4%, with no significant difference between genders. At every age, weight z-scores and BMI percentiles were significantly lower in thin children than normal-weight children. The increment in weight z-scores between birth and the age of 1.5 years was significantly lower in thin children. The only parental link was paternal thinness and thinness in boys. CONCLUSION: Careful observation of body weight from birth is important to reduce thinness at 5 years of age. Paternal thinness may be a risk factor for thinness in boys.