Your chubbiness was envied and admired.

你那胖乎乎模样可令人羡慕了。

His fur had darkened from days playing in the sun, and his belly had lost its chubbiness and become lean from constant activity.

于白天在阳光下玩耍，皮毛颜色变深了；于经常活，肚子也不再圆乎乎，渐渐消了下去。