Could having a healthy diet and the right amount of exercise affect the growth and development of a person ?

Diet and exercise: Not sure what you mean by "growth and development" but there is nothing more effective you can do for your longevity and quality life ( as well as to preserve cognitive functioning ) as to get regular exercise and eat a healthy diet. Actually, connecting with others/limiting social isolation would top the list of "biggest bang for the buck" health moves as well.