According to the University of Wisconsin School Of Medicine and Public Health study if you were to quit smoking and gain weight you will lower your HDL (good) cholesterol numbers. Smoking ages you quickly, suppresses your appetite and causes all kinds of health problems such as Cancer, Respiratory and etc.
In the study of 923 participants and 334 returned and did not quit smoking, gained weight and had no change in their HDL. However, those who had quit smoking improved their HDL cholesterol by an average of 2.4 points, even though they gained an average of 10 pounds. This HDL increase is enough to lower your chances of a stroke or heart attack by 6%. LDL (bad) cholesterol, which normally goes up with weight gain, remained unchanged.
Smoking also causes: lung cancer, mouth cancer, breathing problems and other type of related cancers.