Objectives To explore how fat, lean and body mass index (BMI) track in childhood and how this relates to parental obesity.
Design and Setting Prospective population-based cohort study: Avon Longitudinal Study of Parents and Children, UK.
Method Height, weight and leg-to-leg bioelectrical impedance (BIA) were collected at ages 7 and 11 years, as well as pre-pregnancy parental heights and weights. For BMI International Obesity Task Force thresholds of obesity and overweight were used. Impedance data were expressed as separate lean and fat z scores, internally standardised for gender, height and age and a child was defined as over-fat if fat z score was >85th and very over-fat if >95th internal centile.
Results Data were available for 7723 and 7252 children at ages 7 and 11 years, respectively (6066 at both time points). Of those obese at age 7, 75% were still obese at age 11, while of those who had been overweight 16% had become obese and 20% now had normal BMI. Both fat and lean z scores showed moderate levels of tracking (correlation coefficients 0.70 and 0.73, respectively). Children with one or two obese parents had higher fat z scores at age 7 and showed greater increases in fat thereafter. They were more likely to be very over-fat at age 7 and, of these, 69% remained so at age 11 compared to only 45% with non-obese parents (p <0.001).
Conclusions Children of obese parents already have high fat levels at age 7 and are more likely to remain very over-fat.
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Funding This analysis was funded by a project grant from the British Heart Foundation. This study could not have been undertaken without the financial support of the Wellcome Trust, the Medical Research Council, the University of Bristol, the Department of Health, the Department of the Environment, NIH and other funders.
Competing interests None.
Ethics approval Obtained from the ALSPAC Law and Ethics Committee and local research ethics committees.