You mentioned the body fat scale. At about 2 months after I first starting cycling a year and a half ago, my body fat was at about 16%. After 6-8 months of tandeming and fixed gear riding, it was below 6%. We rode over 3,000 miles in the first year. Something about pulling a 60 pound triplet really tones the muscles.
height/weights
Me: 6'1" 160 lbs
stokette: maybe 3'6" (haven't measured in a while), 36 lbs
stoker: 5'7" 120 lbs
bike: 11' long, about 60 lbs
Occassional trailer and camping gear, 50 lbs