Final answer:
Childhood obesity is a condition where excess body fat negatively affects a child's health or well-being. It can be diagnosed based on the Body Mass Index (BMI).
Step-by-step explanation:
Childhood obesity is a condition where excess body fat negatively affects a child's health or well-being. It is often diagnosed based on the Body Mass Index (BMI). The statement that provides the best operational definition of childhood obesity is 'a condition where excess body fat negatively affects a child's health or well-being'.