For unknown reasons, Yu Ming didn't have much of an appetite recently. He was not human, but he had lived among humans for many years, and that was why he had adapted to human habits in terms of eating. Usually, he ate three times a day, but recently he often forgot to eat because his body didn't feel well.
Even when Yu Ming was eating, he only ate very little, and that was why he assumed he had lost weight in the past few weeks. Perhaps that was the reason why Xue Mingyu could easily throw him over his shoulder and carry him like a sack, right?
Yu Ming didn't know the answer, and while he was still struggling, the Demon King stopped walking. Yu Ming thought that the Demon King would continue to carry him on his shoulder until they arrived at the manor on top of the First Peak, but he was wrong because the Demon King decided to put him down while they were at the river bank.