From personal experience, losing 25 pounds made my cock seem at least an inch longer. It's the fat pad around the base of your cock that hides some of the length. When I was in college, and about 35 pounds less than I am now, even flaccid I hung longer than I currently do. I'm on my way to getting back down to college weight, and having a bigger cock is part of my motivation. It's not just perception, either. You get more USABLE inches. When I was in college, my hard cock was over 7.5" and almost 8. Now, it's just over 7", when I push the tape measure in. When I get back down to my 155 weight, I know I'll be back to 7.5 or so.