First forray into LR4, exported jpeg file size is HUGE!

Hi all,

Basketball season has started and after starting my first team series upload to Zenfolio I only then noticed the file sizes were twice the size of an in-camera jpeg.

Processing from RAW with I guess default export settings, A580 photos average 8-9 MB, and a77 average 16 MB with one at 23MB - for jpegs!

What gives? What is the difference between an in-camera jpeg at 8MB and a converted RAW jpeg from LR4 at twice that size?  Is there some benefit to having the large file size version?  Can I change an export setting and create a more managable file size?  What will I lose if I downsize?

Any help appreciated as the 200 photo series weighs in at almost 3 Gigs.  Difficult enough for me to upload and probably too much for team mates and family to expect to be patient for.

Thanks, JS

On a side note:

This series was from a program the pro basketball team the Minnesota Timberwolves has. They invite young teams to come play on the "big court" for an hour and stay for a Timberwolves game.  Very exciting for the young players and parents alike.  I also did my homework and was surprised that any level of camera equipment was allowed not only for the kids game, but for the pro game as well.  So there I was with my a77, grip, and 70-200 G shooting at a pro sports event.

Go figure.