The average weight for a 7-year-old boy is 50.5 pounds, and the average weight for a 7-year-old girl is 49.5 pounds. However, "average height and weight ratio charts are not truly accurate measures or indicators, especially so for young children and teenagers," says Disabled World. This is partly because children's weight fluctuates so much, especially in boys, as they have sudden growth spurts.
If children are overweight, they usually do not need to diet. It is typically not a healthy choice for kids and teenagers, since they so commonly outgrow their baby fat. If weight is a concern, this is something that should ultimately be discussed with a pediatrician.