One reason is that smoking increases metabolism. Another reason is that a smoker's bones become soft and weak. In addition, while smokers may weigh less, they tend to have more body fat. The fat is distributed in the upper body, chest and stomach. The excess fat in these areas can lead to heart disease and diabetes.
Smoking prevents fat from going into the fat cells.
So LPL sends the fat to the heart and arteries. This leads to fat and cholesterol build-up in the blood, high blood pressure and heart disease. When a smoker quits, LPL moves fat into the fat cells, which get bigger, resulting in weight gain. Metabolism slows down, adding to the weight gain. Just remember that quitters can expect a gain of about 10 to 15 pounds per daily pack smoked, and it can take up to a year to re-establish properly functioning metabolism.