Men have a fat pad right above the penis. When pressing down to the bone in measuring penis length, that fat pad can be up to one and one/half inches deep. That means that losing enougn weight can cause that fat pad to get thinner making the penis not only look longer, but actually be longer.
Sometime in the past it was reported that the flaccid dick length can vary 1 and 1/2 inches just by gaining or losing weight.
I know for a fact that when I was at my heaviest, my penis seemed to have shrunk close to an inch. Now that my weight is back to being only 15 pounds from where my doctor wants it, my penis just looks larger.
Erect penis length isn't as greatly affected, though weight loss or gain does affect the flaccid length.