Answer:
Weight in my belly, Trees on my back, I travel fast in my place, but feet is a feature I lack
Large as a mountain, small as a pea, Endlessly swimming in a water-less sea.
What contains zero calories, but if you consume it, you will probably gain weight?
Some live in me, some live on. And some shave me to stride upon. I rarely leave my native land. Until my death I always stand. High and low I may be found. Both above and below ground.
Flat as a leaf, round as a ring. Has two eyes, can't see a thing.
If itβs information you seek, come and see me. If itβs pairs of letters you need, I have consecutively three. What am I?