Is my daughter eating too much?

My daugther is just about 15 months old.  At her 1 year visit she was 25 lbs and 31 inches.  I suspect that she is closer to 27 pounds now, maybe even more.  She has always been in the 90th percentile and upward and has always had a healthy appetite.  My concern now is that she is eating just for the sake of eating, not because she is actually hungry.  She will eat a meal or snack and seem satisfied but if she happens to see someone with food immediately after finishing her own she starts making "mmmmm" sounds and crying for the food.  She is not the type of kid that whines when hungry if food is not in sight - she could go for quite sometime without really asking for food, but if she sees it, she acts like she is starving.  Is this normal?  Should I give her the food when she asks even if she's shouldn't really be hungry?  Also, lately she seems to have excessive thirst...she gulps down an entire cupful as fast as she can - again, she doesnt ask for it, but if its there she acts extremely parched!  

I just don't want to do anything that will contribute to her becoming unhealthy or obese.

Please advise.

Thanks!

[Renee Radenberg]

Her weight is between the 90-95th percentile and her height is on the 75th percentile for her age. Suggest feeding her on a daily routine of 3 meals with snacks between meals and before bed to see how she behaves. Does she eat with you as a family? Maybe eating together would help if it is not occurring. Some children want to 'copy' what the adults are doing, however, if it continues, then have her checked by her MD.