Hi there, I understand your concerns. I would like to allay your fears a little..yes, he is slightly underweight but not alarmingly so. Till about 5 years, most toddlers have reduced appetite as they are busy exploring and learning new things. My advice to you would be to increase the calorie density of the food he eats. Add more coconut oil, clarified butter, roasted and powdered cashewnuts/almonds so that for the same amount he eats, more calories go in. Cut out juices and excess milk which will fill him up and cause him to eat less. Follow the above and he will gradually eat more and gain weight. Warning Signs: 1. He is LOSING weight frapidly 2. He gets fever more than twice a month 3. He is lethargic and does not want to play 4. He has excessive vomiting 5. He is peeing less than 4 times/ day or more than 12 times/day. If any of the warning signs are there, see a pediatrician. The appetite-inducing medications do not work and may cause side-effects. As long as he is active and does not get repeated infections, there is nothing to worry. Hope this has answered your query satisfactorily. Take care !