When an obese child loses weight, why does she is prone to gain weight in the future compared to an obese adult who lose weight?

Obese people.... ....Whether adults or children, have a higher tendency to gain weight than someone who has never been obese. A child who has lost weight is not more prone to becoming obese than an adult who has lost weight. It's the other way around. Metabolism slows with age, so weight gain tends to be greater in adults.