The words follow through are not a phrasal verb in this sentence. Really, those two words should be hyphenated and then they form the single noun follow-through, which means "the act or an instance of following through (with something)."
This is also a situation where the inclusion of a serial comma between "through" and "or" might have made it more clear that the final phrase starting with "of" contains a list of three items:
- poor planning
- (poor) follow-through
- (poor) persistence
Note that the adjective poor is meant to be applied to all three nouns (planning, follow-through, and persistence), which is not entirely clear from the sentence as written. Personally, I would have chosen to write something like this:
[...] An undisciplined person is removed from any aspect of health simply because of poor planning, inadequate follow-through, or lack of persistence.
This means the same as the original sentence, but the serial comma makes it clear that there are three items in the list, and there's an explicit negative qualifier before each of the nouns.