Bodies are generally pretty amazing in that sense. As long as things go out of spec _slowly_, we will often adapt quite well. In the short term, we will tend to balance even fairly extreme changes out through various chemical processes and in the long term people can even develop heritable genetic changes. (E.g., how people acclimatize and have in some cases adapted to living at higher altitudes[0])
[0]: https://en.wikipedia.org/wiki/Effects_of_high_altitude_on_hu...