Your chubbiness was envied and admired.

你那的模样可令人羡慕。

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，他皮毛的颜色；于经常活动，他的肚子也不再圆的，渐渐消下去。