The WHO Child Growth Standards
The World Health Organisation child growth standards are available online along with details of data collection.
Specifically, weight-for-age charts are available here.
Measurement and Definitions of Obesity In Childhood and Adolescence: A field guide for the uninitiated.
A highly-accessed review by HN Sweeting from the MRC Social and Public Health Sciences Unit in Glasgow.
Available in full on the Nutrition Journal website.
Child Obesity Programmes