just happen to read your post,,
with brthwght 3.5kgs,at 16mnths 21lbs,,he should be around 23.5,,,plus minus 5lbs, is okay,,not a prob,,,so he is around 1lbs/500grams less on an average so to say...can be acheived,,,not a prob.
also note this is just the right time for his teething premolars and molars, so expect loss of apetite/lack of interest in foods or spices,,and more interest in liquids or milk or best is to offer whatever satisfies him !!
now about his schedule :

9.30 am : Oatmeal/Mixed cereal/Wheat + banana + milk (cereal) ==== no comments, avoid gving ne fruits along with the breakfast after 9months,,a seprate serving of fruit is needed for baby...also try toddler/gerber/graduates,,cereal series,,they will help you introduce your baby to new texture and graduate further...they come in various flavours,,go one by one,,cherios too is liked by some babiees,,but start with toddler cereal first !
11.00 : abt 4 oz of milk ==== no comments,,i would recmnd you to give at this time serving of fruit, try n see if he accepts for a couple days or so,,,or else dont mess his current schedule,,,,and give this part of milk as a feed in early morning,,how about 8am ?? see if this helps, him eat fruits as well,,

1.30 : rice with dal + either veg or chicken === no comments,,add in wheat as a part of lunch or dinner,,,its good for growing toddler, prvides him good protein and nutrients,,it doesnt matter even if he takes it in breakfast ! toddlers over 15months are expected to eat around 1/4th-1/2 of an adult serving per dish,,which means he is expected to eat rice,vegie,meat/protein,grain and lentil for a good grwth and a complete meal..

5.00 : apple + milk + cereal === if he sleeps what time he sleeps,,try to give him snack at this time,,instead of cereal.the snack could be nething like roasted multigrain bread/toast/whole wheat toasts/toddler crackers and a serving of yogurt..or replace this time with fruit juice,,now he is ready for 100%,,try offering fresh,,or else gerber is also a good option,,,

7:00 : yogurt ////try to replace this with fruit juice,,,,so that he eats well his dinners !! yogurt is heavier than juice and juices are liquids which are digest,,,or try offering lentil soup,mix vegie or chicken clear soups or just plain tomato soup with lil sprinkle of cheese or some toast/bread crumbs.. so that it gives him good apetite,,soups are said to clear digestive upsets and clear stomach so that body is ready for a real good feed of meal !!

9.00 : rice + dal + some vegetables,,,good,,

offer dessert if your baby seems to b hungry or else, offer a good 4-5pz of milk ( at 16months onwards most toddlers are ready for additives like horlicks,chocolate syrups,complan and nesquik if in US,,,ask your dr which one is right for your baby,, ) most toddlers have shown interest in milk due to these, as down the line their interest in milk kind of disappears...also 1/4th tsp of cardamom pwder in 5oz of cows milk, offering it warm,,improves the apetite of the toddlers or ne adult even ! offer before sleep...

at 16months, your toddler is expected to drink 2-3 feeds of cows milk, 3 times a day,,distribute the feeds to the level of acceptance and dpending his daily diet,,some foods are heavy and those days dont expect your baby to drink milk or ask for food in 2-3hours,,a toddler this young is expected to eat every 3-4hours,,,and around about,,some may go upto 5 hours,,but later than that is not acceptable.
keep trying with juice,,a good intake of liquids is a must,,juices too offer weight gain, thats y its said to give only 1 feed of juice that too best time is the afternoon time so that he eat his dinners well and juices clear his stomach jam incase any due to lunch or brunches,,

offer him variety of fruits, vegetables, meats and add in to his diet, multigrains/wholegrains,,things like pastas are great finger foods and evening meals,,throw in tofu,crushed meat/ground meat,,and vegies,,and offer it as a complete meall...
off your baby mild spices nw that he is 16months,,he needs to introduce to spices,,,so start that,,will help him deal with digestives and improve apetite in long run...
the day you think, he didnt take much milk from morning to evening,,offer dinner less or a pure vegetarian dinner (avoid ne sour foods ), and offer along with it, kheer (cooked rice in milk with some sugar and cardamom),,,its a great way to offer your baby more of milk products,,,
add in cheese to his diet in form of sprinkles/or crumbles with roti or rice,,
and i think this should help,,,
try to start your baby day in morning from 8onwards so that you can add in one more stage of feeding that i talked above,,,early rise and early sleep is a sign of good health,,and a meal every 3-4 hours is a good schedule !

take care, good luck


MM replied. Thanx Hetal. I'll follow ur advice.