Scientists have found that high-density lipoprotein (HDL) in the human body has a preventive effect on heart disease. If you smoke more than 20 cigarettes a day, the content of HDL in the body will decrease significantly. If you stop smoking, the content will increase. In fat people, the HDL content of males declines in their forties, but the opposite is true of females. The HDL content of older women is higher than that of older men. From this we know:. ['Men are more susceptible to heart disease than women.', 'Men are more likely to develop heart disease than women.', 'The older the male, the higher the chance of heart disease.', 'Older men who are leaner have a lower risk of heart disease than older women who are overweight.']