my son is not gaining weight he eats well but still he is 15 kg his age is 4.5 years old

A. Hello, When growing kids don't gain weight as they should, it is called "failure to thrive." Failure to thrive is not a disease or disorder itself. Rather, it's a sign that a child is undernourished. In general, kids who fail to thrive are not getting enough calories to grow and gain weight in a healthy way