what is the reason for not absorption of nutrients in kids and not gaining weight.

A. hi it happens because of many reasons like increased activity level , indigestion, constipation etc so please check it . give high calorie diet like nuts , dry fruits,fresh fruits, milk and milk based products , multigrain food items etc give natural probiotics like fresh curd buttermilk etc more which help to maintain good bacteria in intestine. keep your child well hydrated