Warning: This may or may not be a really stupid question.

Does the weight of the earh change? Has the population increase over the history of man and before caused the earth to get "heavier"? Or does it balance itself out by the amount of food we eat? What about construction? We build all these huge buildings which obviously we consume natural resources to make them, but does that really matter?

Just something thats been on my weird mind as of late and I thought I would offer it up for comment.