A little late to the party but I hope this information helps. I am a 5'5 male with an average base metabolic rate at best. I intentionally ate like crap just to tack on weight. I started the AT at probably 165lbs (74.84kg) and I dipped to a healthy BMI for my height at 145lbs (65.77kg) before Hot Springs, NC.
It seems your lifestyle is healthy to begin with so I wouldn't count on your metabolism getting that much faster but carrying a pack and walking the whole day is going to exercise a whole different set of muscle groups than snowboarding and kayaking. I recommend several things. taking short hikes with your pack fully loaded to see which muscles need