The new guidance is intended for health professionals and those who provide specialist weight management services for children.
The guidance stresses it is "important it is to ensure the family and the child or young person recognise and accept that they are overweight or obese.
"Conversely, a lack of recognition or denial that the child or young person is overweight or obese can hinder uptake and adherence to a lifestyle weight management programme."
Many overweight and obese children and young people may have, or come from a family with, a "history of failed attempts to manage their weight", the guidance goes on.
A family's attitudes towards diet, exercise and the amount of time spent being sedentary should all be explored, it added.
More top news
Merve Buyuksarac, who was crowned Miss Turkey in 2006, was handed a 14-month suspended sentence for sharing a satirical poem on Instagram.
Muhiddin Mire cut the throat of a stranger at an east London tube station "in revenge for the fight against IS", a court heard.
The significant development came after a forensic re-examination of a palm print left on a getaway vehicle.