Obesity indices among infants and their parents, Shiraz, Iran

Background: Infantile obesity is becoming increasingly recognized as one of the public health problems in Iran. Objective: Obesity charts of a cohort of 317 healthy infants and their parents living in Shiraz (Southern Iran) are presented and the familial pattern of infants’ obesity with that of its parents explored. Methods: An adjusted weight-for-height index was used to develop power type obesity indices, Ip=W/Hp. Polynomial modelling was used by applying the Healy-Rasbash-Yang (HRY) nonparametric method to estimate age-related smoothed centiles of obesity and dynamic obesity charts for infants and their parents are presented. Principal component analysis (PCA) was applied to the data as continuous variables to analyse familial pattern of parent-infant obesity structurally. Results: The optimal value of p was found to be 2.5 for infants and 1 for their parents. Infants’ obesity increases from birth to six months of age and decreases thereafter until the age of 21 months when it became stable. Obesity indices and circumferences sizes were reduced to two principal components interpreting infants as well as family obesity. The first principal component evaluates infants’ obesity as a combination of obesity index as well as their arm, chest and head circumferences. Also the second principal component combines mothers’ obesity and her arm circumference, while father obesity did not influence familial obesity structure significantly. Conclusion: Obesity is an age related phenomenon and dynamic charts presented herein are appropriate practical tools to assess obesity in both infants less than two years of age and their parents.