Backpack Angst

I loaded up my backpack last night and found it had mysteriously increased in weight from 9 to 12 kg. I went for a 15km walk in the hills this morning and I think it’s a bit too heavy. The rule of thumb is that your backpack shouldn’t exceed 10% of your body weight, or 9 kg for me. Of course, I could always stay a bit longer in Bologna and eats lots of rich Bolognese food and get my weight up to 120kg but there’s no time for that unfortunately so I’ll have to make some hard decisions. Maybe I’ll even have to jettison my rubber ducky Or even worse my Vegemite.
PS I got it down to 11kg plus 2kg of water and this was fine for my walk. After a week I forgot I was carrying it !