Well, when you smoke cigarettes some say it is an appetite suppressant. I would always just have a cig before and after a meal, not in place of 1 lol. Also when you smoke you're heart rate is increased, so your metabolism is slightly increased. I remember reading heavy smokers burn about 200 more calories a day than non smokers.
Screw that, though. The health risks far outweigh the small positives smoking brings. I remember my first day at the gym I couldn't run for 5 straight minutes at a steady pace on a treadmill without coughing until I was on the verge of death haha