Something I've always been curious about--- as they age, do shorter
people struggle with their weight more than taller people?  Is there
any correlation to keeping physically fit and height?

As a broader question, is there a way to predict if a young adult (say
in their twenties) will end up struggling with their weight as they
age?

It's generally accepted that life style is the major influence and, if
so, future ratios would be impossible to predict.

I suspect that females are also more likely to have problems.

Probono still has his guardsman's figure, I assume.  :)

I expect that larger persons can carry/hide increased weight more
successfully than short people.

As to females "struggling" with the problem more than males, IMHO male
clothing is more "forgiving" to the problem of overweight.  Maybe if
women designed men's clothing, we males would be more conscious of the
problem.  On the other hand, with women's wear, there is a tendency to
want to emphasized a couple of points, and the best way to do that is
to that is to also emphasize a slim waist (at least in the Western
World).

The world is unfair.

Sorry, Myo, but I've never been a Guardsman.

Always Trooper C***** of the 10th Royal Hussars (PWO), Sir!

Er, ah, yes, Trooper Bryan, I recall now.  That was your last question
before you disappeared into the Highlands.
I was using the term in the general sense, and hope it still applies. 
Once saw a photo of Peter Ustinov on horseback  - playing Geo IV, I
believe.  Poor horse.
Myo