Your chubbiness was envied and admired.

你那胖乎乎的模样可令人羡慕了。

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

由于白天在阳光下玩耍，他皮毛的颜色变深了；由于经常活动，他的肚子也不再圆乎乎的，渐渐消了下去。