One thing about all Trump's Generals.  They're all super fit looking people.  
Trump seems to like that.  Notice how he took Jared (metro skinny) and Ivanka (ideal vision of female) into the Whithouse, but left Don Jr. OUT.
Sessions?  Obviously in better shape than Guiliani and. . . Christie!
And, the Generals obviously value fitness.
Kelly may be important to the country to the extent he may impose a physical conditioning regimen, a la Marine Corps. upon Trump.  
Alternatively, as Trump's physique becomes more and more a focus (Putin, with his vacation photos is DEFINITELY making it an international issue) Trump may get oppositional defiant and get rid of all the fit guys.  
Then, the changes are Don Jr. as Senior unpaid advisor, Guiliani as Chief of Staff, and Christie as AG.  
We need to subtly, as a country, sway POTUS to get in better shape so that this isn't an issue going forward.