Is there a way to increase the carrying limit?

Solution 1:

The Strong Back achievement is based on whether or not you killed Aryan La Valette. If you let him live and then meet up with him in the dungeon you get the ability. If you kill him, you miss out.

There is also a mod floating around the net that makes all items weigh nothing if that is to your fancy.

Solution 2:

The "Strong Back" ability grants an additional 50 carrying capacity. It is gained by picking up a large amount of loot in the La Vallette dungeon in the prologue. However, there are reports that some people get the ability and others don't, so it may be buggy, or you may just have to collect every single scrap of loot.

Additionally, some pieces of armor can increase your maximum load.