Blanket recommendations of so many kg or litres make absolutely no sense. Body mass, season, resilience and whether you can really afford the expensive really lightweight gear all make a difference.
The CSJ website recommends no more than 15% of body weight, and the Complete Walker IV (an American classic) recommends 20% from the skin out (ie with clothes, boots and other worn equipment) for comfortable trekking. These work out to be much the same target weight.
A lighter person (<60kg) who has good cold tolerance (resilience) able to afford lightweight gear and walking in summer could reasonably expect to be able to get down to a 6kg pack weight on the
Camino Frances, even less if they carry little food.
A larger person (>80kg) who isn't so resilient walking in autumn and with some lightweight gear might expect to carry over double that. Carrying food for a couple of days will add even more if they are walking one of the routes where there are less towns and villages to purchase meals or provisions.
These calculations are based on the algorithm suggested by the authors of The Complete Walker IV. This algorithm gives results consistent with my trekking and pilgrimage experience, and is also consistent with what I have known other pilgrims to achieve.
For example, all the gear that I needed on the
Camino Frances in early spring fits comfortably into a Deuter Guide 45+ pack (it expands to 55li if needed) and in that pack weighs just over 10kg with an allowance of 2kg for water and food. I am about 90kg although I should probably lose some, but this means the overall load is well within the 15% CSJ recommended maximum.
I do agree with the general point being made to reduce pack size and weight. Generally, the lighter one can pack, the faster one can walk comfortably. One can either cover greater distances in a walking day, or cover the required distances quicker and shorten the walking day.
