Your inventory's capacity is communicated by how much gunk and rot covers the menu. Having a light inventory will invite peat moss to grow across the screen.
When you've a full pack, the management screen will be covered in mud, rot, and small bugs you have to clean off your belongings. You can continue to carry lots of things, but they will decompose more quickly.

Different combinations of objects in your inventory leads to different rates of rot and different passive buffs or debuffs. Having objects that represent a variety of energies or materials will keep you neutral, while specific combinations could lead to boosts in speed but increase your hunger, etc.

Maybe certain objects attract animals.