Deposition of lipids can also occur within the cells found in the lining of blood vessels, particularly those forming the walls of major arteries. Here accumulation of lipids leads to formation of fatty plaques, resulting in atherosclerosis (hardening of the arteries), which limits blood flow and thus can lead to heart attacks and strokes. At other sites, interruption of blood flow can also produce kidney failure or gangrene. Excessive accumulation of lipids is also a major factor in type two diabetes and hepatic steatosis (fatty liver). Excess consumption of alcohol can cause changes in the way that the liver breaks down and stores fats, leading to more severe conditions such as cirrhosis. Fortunately, the fat droplets can still be broken down in the cell, so the condition is reversible with reduced consumption of alcohol. All this bad news leads to the reasonable question of whether we might not have been better off without fat cells, but they function in response to evolutionary pressures, allowing food storage that may well have helped us survive in times of shortage, and also allowing many other mammals to survive severe winters by hibernation.