My own experience of being a very overweight and unfit Pilgrim taught me this.
Your mileage may vary.........
On my first Camino I got a Personal Trainer and did lots of training............
and got injured due to my excess bodyweight.
I walked my first 800 km Camino injured as a result..........and still very overweight.
I walked 18-25 km / day with the odd 30 km (that nearly crippled me).
I could barely walk 10 kms / day by the end.
2nd and 3rd Caminos, I did some very 'gentle' exercise with my wife Pat who was coming too.
We also walked much shorter days for her. 18 km average.
We tried to lose a bit of body weight without much success.
But the shorter days led to only 'manageable' injuries. Plantaar Facitis and Achilles Tendonitis.
No shin splints this time.
4th and longest Camino (1200 kms this year)
I focussed 95% on weight loss. with very little training.
I lost 18 kg through intermittent fasting.
The Camino was easy this time without any injury or discomfort.
I managed to just get into the BMI range of overweight rather than my normal 'obese'.
So I was still 'fat'. But it made a huge difference.
My 'training' these days consists of a few gentle 5 km walks in the weeks before I depart.
Maybe 2 / week. Carrying a light pack.
Then I 'warm up' on Camino, building up my days slowly.
10 kms, 14 kms, 18 kms, 20 kms etc. My sweet spot is 20-25 kms / day.
I think this gradual 'warm up' is key.
Many people seem to get injured in the first 7-10 days by traying to walk too far too fast.
IMHO, you need to ease into it unless you are starting out as a fit strong hiker!
I have a regular debate with my business partner who is really skinny.
He keeps telling me to exercise more prior to my Caminos........
As this will help me lose weight.
I just ask him how much exercise it would take to lose the weight gained by eating a Big Mac!
(A brisk walk for about 90 mins)............
Much easier not to eat the fatty/excess foods in the first place
Which is hard for a food and wine lover...........but it's still easier than becoming a gym junkie and seeing slow progress.
Your 1 lb / week is a sensible and 'maintainable' goal.
Too big a goal is very hard to maintain.
When in 'training' for a Camino I weigh myself daily and have charts of my progress.
I start out at 1 kg / week and tail back to 500 gms as I get closer to my goal.
I start about 6 months out.
Keeping the weight off post Camino is my next challenge
But hey. You sound determined.
You just need to find a preparation regime that will work for you!
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