INS and lung carcinoma: In addition, physical activity can significantly reduce insulin, glucose, and triglyceride levels, and increase the level of high-density lipoprotein cholesterol, which may be associated with reduction in lung cancer risk.[53] Another possibility is that physical activity may enhance immune system function[12,38] by increasing the number and activity of macrophages, natural killer cells, lymphokine-activated killer cells, and lymphokine regulated cytokines, as well as increasing mitogen-induced lymphocyte proliferation rates.