in terms of zombie survival, I have discussed this at length with my children, and we believe that while some fat is desireable, excess fat impeding swift movement will ultimately prove poor for survival. you are going to need to be mobile, fit, able to scavenge over great areas, capable of vigorous physical activty against zombies, of hiding, but most important is the ability to cover ground. fat will be bad. sorry, i’d go for lean over fat, ideally a caveman like build, thickly muscular with an overlay of fat but not enough to impede movement.