Sloths have an incredibly low metabolic rate and need only a few leaves and twigs for nutrition, along with a very slow digestive system leading to their sluggish pace. In combination, the sloth’s anatomical structure differs from other mammals in having very long arms with very short shoulder -blades, which allows them a large reach without the effort of too much movement, and adds to their languid style of movement.

Source: Safaris Africana