Sloths can take up to a month to digest a single leaf. 

For a sloth, there’s no such thing as rushing through lunch — in fact, a sloth can take up to a month to process just one leaf through its digestive system. Their leafy diet is low in calories and difficult to digest, so they’ve evolved a slow metabolism and a digestive system that allows food to remain in the gut for a remarkably long time. Microbes help break down tough plant fibers and unlock nutrients and energy from the leaves they eat. 

That slow digestion fits with the sloth’s energy-saving lifestyle. A sloth’s metabolic rate is just 40% to 74% of what would be expected for another mammal of the same body weight. Sloths conserve energy by moving slowly, eating relatively little, and spending much of their time resting. Because food can remain in the digestive tract for weeks, sloths typically defecate only about once a week.