How does a leaf-based diet affect a sloth's metabolism?

A sloth’s leaf-based diet is the primary driver of its unique physiology and slow-moving lifestyle. Because leaves are low in nutrients and calories, sloths have evolved a metabolism that operates at only 40–45 percent of the rate expected for other mammals of their size.12

This slow metabolic rate is an adaptation designed to conserve energy. To process their fibrous, chemical-rich diet, sloths utilize large multichambered stomachs where digestion occurs very slowly; a single meal can take up to a week to ferment and process.123

Additionally, sloths are heterothermic, meaning they have imperfect control over their body temperature. Their body temperature typically ranges between 25 and 35 °C (77 and 95 °F), but it can drop as low as 20 °C (68 °F), at which point the animals become torpid to further minimize energy expenditure. By maintaining this slow-paced existence, sloths successfully survive on a diet that would be insufficient for more active animals.31