obesity is a less severe problem than polio, rickets, iodine deficiency (goiters), measles, mumps, the plague, avian influenza (as i recall, the 1918 flu virus was sequenced and found to be avian), you get the idea.
I do understand your argument that a healthy person today is less healthy than a healthy person from history. however, even without considering fatal illnesses, i think you are discounting the myriad ways that any given individual slowly destroyed their body in order to do the things necessary to survive
the rest i don't really have a disagreement with, but you seem to have specifically claimed that we were healthier back then as long as we don't count all the ways in which we are healthier now. to be fair, you would also have to include the occupational hazards that affected the health of the people, from the mercury poisoning that hatters faced, to farmers working out in fields while not having sunblock, to simply not understanding hygiene. think about tanners who literally worked with a pit of feces and bacteria, think about how human waste was once thrown out of windows, or how people used to drink (many still do) from the same river in which the next town upstream bathed their livestock in.
keep in mind this discussion is about the advancements we have made through history, including medicine. overall, we are far and away healthier than we were pre-penicillin and vaccines.
the illnesses and health threats we face now are simply less severe than those that were faced 100 years ago.
that isn't to say we aren't in a peculiar position regarding our health at large. while we have solved many of the more complex health problems form days of old (cancer is the big one we still have to deal with), we are starting to let the simple things slide.
this is a bit disjointed, but it's almost 6 am, and i don't feel like editing it to the degree i now realize i should.
i swear, i have lost the ability to just make a simple post.