Your chubbiness was envied and admired.

你那胖乎乎的模样可令人羡慕。

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

于白天在玩耍，他皮毛的颜色变深；于经常活动，他的肚也不再圆乎乎的，渐渐消去。