I'm told (I'm no expert) that in order to lose weight by walking it's best to do several consecutive days. As pointed out by another poster if you go and have a big day out in the hills then you come back starving. After 2 or 3 days of repeated work your body then adjusts to "fat burning mode" much more efficiently.
My own experience bears this out - first couple of days on a walking trip I eat like a horse, but after that my appetite subsides and I hardly feel hungry at all.
I'd tend to go along with what most people on here are saying - walking is the best training for walking. And slightly increasing the load in your pack does help.
Most people stiffen up after a walk because they're not used to having to make the fine control movements which moving over uneven/steeper terrain calls for so they get tired and tense up. This is borne out by the number of people I come across who are much more "gym fit" than me but suffer really badly in the hills after a big day out, especially if it's steep or rocky.
Something that seems to help, according to my physio, is working on core stability as well as more general fitness by using one of those great big excercise balls or doing some Pilates-type excercises. This improves your balance, posture and fine motor control allowing you to be more relaxed when moving over uneven terrain.
I'm geting plenty excercise at the moment from chasing sheep out of the garden. They are on a mission to devour all my trailing jasmine and the new shoots on the honeysuckle, as well as stealing the bird feedersand carrying them off. And they laugh in the face of my rather amateurish attempts at mending the fence
Ian
www.mountainfreedom.co.uk