My training partner and I have had this discussion for years now, and since our training and diets are so similar but our body types and genetics are so different as well as overall height difference that We believe we have come to a conclusion. I am almost 6'5" and 225 with bf fluctuating at 10-to 13%, while he is 5'5" and about 190 with bf at 18% average. We are both over 40 also. While his body type is a large chest/upper body and shorter thin arms and legs-i was always a really skinny guy with low bf all my life. It was hard for me to gain large well defined muscle groups, and gain weight without fat- but i have reached my goals with a lotta hard work and a very sensible diet. He has had to work much harder physically and his diet is very restricted-one cheat meal and blam his body just bloats up. Genetics play a role here, we know that 4 sure just by our experience and the fact that we grew up together and know each others familes. Just wanted to know what anyone elses experiences are, Thanks.