Photo Copied from Dr. Foster's and Smith. I hope they don't mind, but I have always maintained that Neutering males dogs did none of the things the vets said it would, make them less aggresive, less likely to run off, and did every bad thing the vet said it wouldn't like make them fat, and lazy, and unhealthy. I have had one neutering male dog(lost the argument with my mom) and several intact. The intact males were never overly aggressive, and in fact stayed lean and healthy all of their lives until they died. Testosterone promotes lean muscle mass.