At the onset I would say no cypon
And regarding his weight, usually babies triple their birth weight
by 1 year. So he should have been around 10kg by 12 months. At 16 months he is 9.2 kg, which is still okay and not alarmingly low. So relax.
As kids start exploring the outside world, they start showing less interest in food.
Do not force feed him at any point of time. If you do so, feeding time will become a battle field, unpleasant to both of you.
So allow him to play and offer him food.
Offer him food in attractive colours, shapes and tastes. Keep showing variations.
Allow him to feed by himself... you may try finger foods.
Give high calorie food by fortifying all food with ghee, butter, oil or cheese. You may give him peanut butter with bread etc.
Give him nuts and dried fruits.
Give eggs in different forms like scrambled eggs.
And you may visit a Pediatrician
and ask for iron, zinc and multivitamin
supplements. If he has micronutrient
deficiencies it will get corrected. And get his throat checked to rule out any issues there.
Do not give him lot of milk as it will reduce the solid food intake.
You may also feed him in the presence of other babies... some kids start eating seeing others doing so.
Do not give cypon.