In simple terms arteriosclerosis. That's essentially when the walls of arteries start to become thick and harden, most commonly due to older age-- but it can also start to build up due to fats and cholesterol. Naturally, when something becomes hard and thick, it looses it's elasticity, so your answer would be arteriosclerosis.
Arteriosclerosis is described as a cardiac disorder that results in hardening of the arterial walls. This can affect elasticity, and in turn blood circulation and blood pressure. The illness is different from Atherosclerosis, as Atherosclerosis is a buildup of debris in the artery (Plaques forming from fat deposits, platelets, clotting, etc..) Many times though Arteriosclerosis and Atherosclerosis work in tandem to worsen cardiovascular health, greatly increasing chances of Aneurysms, Emboli (Traveling clots), or Thrombi (stationary clots)
First, because you need to be careful of what you are eating and should not eat. Second, if you don't care about what you eating it could be really dangerous.
Metabolism rates gradually increase and peak at around 16 to 17 year old then start to decrease. Studies show that men generally have a higher metabolism rate than women do. This means that a 65 year old woman would have a lower metabolism rate then the 65 year old man. The teenagers would have very fast metabolisms.