My theory is that being thin (preferably anorexic-looking) during the growing period (say 13-21) results in a larger penis. This is because exercise increases testosterone. There is also better blood flow to the penis. Exercise makes you hornier - so more spontaneous erections. I believe that it is these frequent spontaneous erections that contain a lot of pressure due to the higher blood flow - that maximises penis size. This strong pressure expands the penis. A really fat obese guy that did no exercise would have a small one. And no - I dont think it is just because of the fat pad making it look smaller. Just going on my own 10 years + experience of viewing porn - it is nearly always the really skinny (almost anorexic guy that have the huge ones. Think danny d or ramon from bangbros or Charlie Mac And no - I disagree it is because fat guys are less likely to be in porn because they are fat. The other thing that I think can reduce size is applying too much pressure in masturbation. This can damage the 3 spongy chambers of the penis and so energy goes into repair rather than growth. Just some examples: https://www.lpsg.com/members/happyboi.495383/ http://hungkidd.tumblr.com/post/110356236730/frenchamateur-aaron-moody https://www.reddit.com/user/wanttoshareit/submitted/ https://www.reddit.com/user/Ferocious245/submitted/ https://www.reddit.com/user/UKsweetguy/submitted/ http://imgur.com/HnvefMV http://theteenboy.com/video/6098/biggest-teen-cock-cumming http://40.media.tumblr.com/0db697172cf120449d8d4eec4ed0b98f/tumblr_ndwm5yMlZG1tlla6oo9_1280.jpg https://twitter.com/domthestud?lang=en-gb http://ballerprinze.tumblr.com/post/112853717985/biggerthenyobf-my-dick-been-growing-in-length Example of a fat guy with small penis: http://imgur.com/dQWYM8p See tinydick reddit: https://www.reddit.com/r/tinydick - most are fat and out of shape I have my doubts about jelqing - in theory it is the same as my theory above - just greater blood pressure. My main doubt about jelqing is that it damages the 3 spongy chambers - so on erection - the erections aren't as strong and so in the end there is less pressure.