My 1yr old son is always hungry?

He 12 months old, and eat's so much. He will eat a whole piece of pizza, and a whole grilled cheese sandwich and still be hungry. Those gerber toddler meals don't even fill him. He's not even a big baby. He's only 19lbs 8oz and 29in. He's in the 10th percentile for weight and 15th for height. I'm just wondering if I should start trying to monitor his intake? I don't want to starve him, but I'm worried about him becoming overweight. My cousin overfed her kid since she was a newborn and she's now a 65lb 2 1/2 year old. So I think i'm a little more paranoid than most people. Thanks!