Helo theodora,
There are literature which shows that childhood obesity persisit to adulthood. But this is not always the case. changing diet and kind of activities that a child engage on, can significantly change the weight statu of your child.
Try as much as possible to reduce the amount of junk foods that a child eat per day, as well there should be a cut down of the number of times a child get food. This doesnt mean that a child should start fasting, never. But there should be a clear schedule for a child to eat.
Consumption of foods rich in protein and vitamin has also been found to have significant impact on child's weight cut dowan. For example you can develop a habit of having more green vegetables and fruits than carbohydrates. Little of vegetables and fruits are stored in the bod compared to carbohydrates.
Simple exercises, such as walking, playing with others and having fun makes a child to loos e some of the weight. But the impact of this may not be seen immediately.
Goodluck!!!