Why we use the singular form when we talk generally about "lifestyle"?

Question

Both examples are extracted from The Guardian newspaper.

Clark points out that Coca-Cola is at least promoting its Coca-Cola Zero at the Rugby World Cup later this year rather than its full sugar Coca-Cola as it did with its London Olympics sponsorship, but stresses that a healthy lifestyle “is about what goes into your body and the effects that can have, not just running around a bit to burn off a few calories”.

If I wrote the above paragraph, I would write "healthy lifestyles" are bla bla bla. This is because the paragraph is generally talking about "lifestyle" which is a countable noun. The following example was extracted as well from the Guardian:

Other initiatives include equal attention to mental and physical health and partnering with day-care facilities, schools, workplaces and others to embed healthy lifestyles.

What I missed here?

Answer 1

You are right that "lifestyle" is a countable noun. And the way you would write the sentence, "healthy lifestyles are bla bla bla," would be fine also.

Information that is true in general for healthy lifestyles can be attributed to all lifestyles (plural) or to a random instance of a lifestyle. If it's true for all,it's true for each.

This is true for most countable nouns:

"Horses can be temperamental." = "A horse can be temperamental."

"Don't take prescription drugs that were meant for someone else." = "Don't take a prescription drug that was meant for someone else."

"You can buy textbooks in the bookstore." = "You can buy a textbook in the bookstore."