The panda has gut structure, gut function, and gut enzymes like a carnivore.
The panda does not have multiple stomachs, nor an enlarged cecum, nor the gut microbes found in animals that eat diets composed largely of fiber, like cattle and sheep.
A study published in the Proceedings of the National Academies of Science states: "The giant panda genome codes for all necessary enzymes associated with a carnivorous digestive system but lacks genes for enzymes needed to digest cellulose, the principal component of their bamboo diet."
Yet wild giant pandas consume around 20-40 pounds of highly fibrous bamboo stalks and leaves every day.
The San Diego Zoo states that the small Red Panda's diet is 95 percent bamboo.
The Smithsonian National Zoo states that "A wild giant panda’s diet is almost exclusively (99 percent) bamboo."
At the Talk Origins site on human evolution, Douglas Theobald, professor of biochemistry at Brandeis University writes "... even though humans are herbivorous, the small human caecum does not house significant quantities of cellulase-excreting bacteria, and we cannot digest more than but a few grams of cellulose per day." [Emphasis added]
Leaving aside for the moment the interesting fact that this staunch defender of evolutionary theory describes humans as herbivorous, the panda's ability to digest cellulose is similar to humans. The gut microbes of pandas digest very little of the fiber the pandas consume; 92 percent of cellulose a panda ingests ends up eliminated in its feces.
“Each facility feeds a steamed grain mixture comprising 13–56% of the diet on an as-fed basis, animal products (milk, eggs, and/or meat; 8–25% of the diet), and bamboo (17–82% of the diet). Seasonally available fruits and/or vegetables are sometimes included (0–29% of the diet).”
“At the San Diego Zoo, pandas are offered bamboo, carrots, yams, and special leaf eater biscuits made of grain and packed with all the vitamins and minerals pandas need.”
"Actually, polar bears in captivity live considerably longer. But shouldn't an evolutionarily novel diet destroy their health? This is yet another example of how Paleologic is no substitute for experiment and observation."
From Polar Bears International:
"In the wild, polar bears live an average 15 to 18 years, although biologists have tagged a few bears in their early 30s. In captivity, they may live until their mid- to late 30s. Debby, a zoo bear in Canada, lived to be 42."