A new and expanded definition of childhood overweight and obesity expected later this year is causing concerns that many healthy children may be unnecessarily labelled as having a disease.

A powerful “expert committee” in the United States has tentatively decided to reclassify children who are currently called “at risk of overweight” and refer to them in the future as “overweight.” Those familiar with these definitions say that such a change could lead to a dramatic expansion of prevalence estimates, with 25% of American toddlers and almost 40% of children aged …