Giant pandas are really adorable bears that whenever you see one, you just want to hug and cuddle it. But did you know that giant pandas are the new couch potatoes of the animal world?

In a recent study published in the journal Science, researchers in China revealed that giant pandas are as sluggish as the slow-moving three-toed sloths due to low levels of physical activity and thyroid hormones. Lead study author Fuwen Wei, a biologist of the Chinese Academy of Sciences' Institute of Zoology in Beijing, said that they discovered the daily energy expenditure values of giant pandas are substantially lower compared to similar-sized animals, ABC News has learned.

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Additionally, the brains, liver and kidneys of the pandas were also found to be smaller than the organs seen in other bears. And as revealed in the study, their low thyroid hormone levels, which are important for regulating body weight and energy, contribute to their sluggishness. Their thyroid levels are only a fraction of the usual mammalian levels and is comparable to a hibernating black bear's hormone levels.

Meanwhile, as the reasons of the giant pandas' laziness are revealed, here are 3 things you should know about this distinct bear.

1. Pandas are the rarest members of the bear family and are classified as endangered species. As per South China Morning Post, there are about 1,600 pandas living in the wild and another 300 held in captive in China. Their natural habitat lies in the mountainous southwestern part of the Chinese nation.

2. Giant pandas achieved the low metabolism through a series of morphological, behavioral, physiological and genetic adaptations during their long evolutionary history. According to Rapid News Network, their low metabolism is correlated with their very low thyroid hormone levels that were linked to a genetic mutation in the thyroid hormone synthesis pathway that is unique to the pandas.

3. When moving around, giant pandas use only half the amount of energy as of that a stationary human. One factor cited is the very little nutrition from their diet of bamboo. That's why these black-and-white cuddly beasts need to save energy, Daily Mail reported. Since their digestive systems originally evolved to digest meat like other bears, they poorly adapted to digest bamboo.

Giant pandas also move at very slow speeds in the wild. However, there is one of the few activities that these lazy giant pandas do spend energy in and it is urinating. These bears produce five liters of urine a day, which is significant for the animals for scent-marking territory.

TagsGiant Panda, Giant Panda Facts, Panda Bear, Science