First fun answer:
90% of the European population can drink milk because of domestication of caws 8000 years ago.
90% of the population of some Asian countries can’t because they did not have the tradition of using caws for food and milk.
So give us another 10 000 years and we will adapt to fast food and junk food and it will be no longer unhealthy :)

Now real answer:
Yes if we survive long enough there will be many human subspecies. Terraforming planet like Мars will be extremely slow (100 000 years) and hard. It will be faster to change the population (high resistance to UV light and low pressure).
The permanent population of space stations in the ring belt will benefit from resistance to low gravity and so on…