Is my 16 months old overweight?

Sounds like he has a healthy appetite! I wouldn't stress about it if you have shared your baby's diet with his doctor and he/she isn't concerned about his weight. The doctors do seemed to be concerned earlier on with childhood obesity these days and rightly so, but at 16 mos it is very hard to restrict them of a wide variety of nourishing foods because they have such a long growth process ahead of them. Now if he is 6 and in the 97th percentile there would be no problem in restricting and monitoring his diet but as long as he is healthy and tested negative for any thyroid problems I would just let him enjoy healthy foods somewhat moderately.