One of the worst things that ever happened to pharmaceutical industry profits was the the discovery that most ulcers can be cheaply cured with antibiotics (which won the discovers a well deserved Nobel prize).
Even after this ulcer drugs were hugely profitable. I cannot remember the numbers from when I was an analyst covering them (more than 20 years ago!), but at one point a very big proportion (maybe even most) of Astrazeneca's profits came from their blockbuster ulcer treatment. Imagine how much more profitable that would be without a cheap cure around!
Gyms are not the solution, nor are health food stores. Far more people join gyms than make use of them. You can keep fit going for walks or running or a multitude of cheap things. IMO the problems are lack of time for exercise and money for a healthy diet.
Poor people have a far worse diet than rich people because they have to fill up with cheap junk. Junk food takes less time to prepare. I have ready meals sometimes because I am tired. Some people have to do it all the time, and they do not have the money to be fussy about how healthy the meals are.