U need to take care of him now only only weight is growing or height also. If u can't give him time make him indulge in basketball or football classes. It will help. Change his diet routine. Include more fibre through sprouts, salads, soup, channa murmura or sandwhoches.reduce butter , ghee intake. No fried foods give skim milk. Give curds and buttermilk. No sweets.sugar restrict.no chocolate. Walk atleast start at home make him run. Make habit of using stairs. On weekends take for swimming. No juices or cold drink. Fruits only give him in morning. Avoid eating too much at time. Small and frequent meals meet dietician