I gotta go with the diet and training, too.
BUT. When i got my bike it had been turned into a 35lbs+ porker that some dude bought his girl friend and turned it into a comfort bike. Fat dude saddle, riser stem, kick stand, the whole nine yards. A Few hundred dollars and a new lx/ xt drive train later, minus fat saddle, kickstand, and risers, it comes in at 27lbs. Lighter than my buddy's Tassajara.
Its doable. But make sure you can keep up with the bike first.