How do pandas have such a big body mass when their stable diet is bamboo?

Answer 1

Many of the largest land animals that ever lived have been herbivores. Bamboo provides the carbohydrates and proteins necessary for the calories and nutrients to support a large warm blooded animal.

Answer 2

Precisely because they eat bamboo. Ever noticed that herbivorous animals, e.g. cows, horses, elephants, etc. are large-bellied? It takes a lot of vegetal volume to extract the calories required to sustain the basic needs of a mammal organism.

Answer 3

They eat VAST amounts of bamboo daily. I cant remember the actual wieght but they spend like all of their day eating bamboo and they need fairly large areas of land to support just one panda because of the amount they eat.

Answer 4

Volume of food eaten. Look for example at the Elephant or the Hippo.

Then there are the whales - the largest of which is the Gray Whale (almost extinct) which feeds on microscopic organisms.

Answer 5

They spend most of their waking hours eating, fuelling up as much as possible.

they move around very little and don't run, conserving as much energy as possible