Bit of both.
Go to the gym and burn at least 500 calories 3 or 4 times a week, and don't drink during the work week, all while eating mostly fruit and vegetables.
I figure my body burns about 2500 calories a day, and I'm putting into it about 1500 max (today I'm up to ~500), and cutting down on all of the beer cut out 600 to 1000 kCal a day from my diet.