Smoking has its ups and downs. Smoking several packs a day will keep your weight down. Nicottine is a metabolic enhancer. That is probably the only good thing I can think of as far as smoking goes though. Everone knows the long terms, (lung cancer, ateriosclerosis, etc), but like the other guys said it will hurt your ablity to workout. Smoking will lower your body O2 saturation and will especially hurt aerobic performance.