You can carry more if you have sturdy hiking boots made for heavy hiking. I would estimate that you could carry 50 pounds, but that you would not enjoy it very much. My guess is that you'll try to stay under 40, even if that means not packing all your food at once. Know where there are water sources. At almost ten pounds a gallon, you will only want to carry what you need to get from each reliable source to the next.
I don't mind carrying a little extra weight if I have the right boots; a twisted ankle is not an option.
Although, there is nothing quite like the freedom of carrying less weight.
Pack everything you think you will need, put on your boots, and go a mile.
1. Imagine that mile times 5, only a little more difficult each time, and if all that seems OK enough to still be fun, then that is your max weight.
2. Imagine that mile times ten, only a little more difficult each time, and if all that seems like fun, then you've got the weight just right!