Strong correlations have been made between high levels of blood cholesterol and the risk to suffer Alzheimer's disease (AD). The question arises on how a peripheral event contributes to a disease that so severely affects the integrity and function of the Central Nervous System. Hypercholesterolemia has been also associated to peripheral metabolic disorders like diabetes, obesity or atherosclerosis that, in turn, predispose to AD. Here we review data, which point to alterations in blood cholesterol levels as a link between these metabolic disorders and AD. We describe and discuss common, cholesterol-related, molecular mechanisms and strategies to fight these conditions that, altogether, constitute a major cause of death in our societies.