No.
The biggest problem is the design of the human knee joint, and knee weaknesses have caused the bulk of 4F classifications and failures to complete boot camp since Black Jack Pershing instituted the boot camp system during the Great War.
I get that it is fun to jeer at lazy fat people, but most people have never been physically capable of meeting service requirements.
I am sure that historically you are correct as far as “4F classifications”, but that is not what I am talking about. By far the largest disqualifying problem for young people who do not qualify for military service these days is that they are too fat. I do not find this to be funny in any way at all... and my intention is not to jeer at fat people... This is just a sad fact about the youth of America.
http://www.businessinsider.com/heres-why-most-americans-cant-join-the-military-2015-9