Diet vs. Exercise - which is more important?

Your entry about the Big Mac got me thinking... are diet and exercise equally important when trying to lose weight? After reading about the Big Mac and the 1 hour of spinning I personally came to the conclusion that diet is actually more important.

Stop and think about the growing epidemic of childhood obesity in America. Have you noticed that all the public service announcements and articles about this topic are focused on getting kids to be more active? (e.g. http://www.cdc.gov/youthcampaign/) Is it reasonable to ask a kid to go to a 1 hour spinning class each time they eat a Big Mac? Or should we be focused on not letting that kid eat a Big Mac in the first place?

Some "food" for thought.

(Hey Al, can you look up how many calories per hour 'thinking' burns?)