What is a good word for when something is theoretically correct but not useful in a real world context?
E.g, it's often said that "drinking water burns calories" but it actually turns out that after drinking cold water, your body warming that water up burns something like a dozen calories...not exactly "much."
So that advice is said to be?
impractical/unfeasible/ From The FreeDictionary:
not practical; not workable or not given to practical matters; "refloating the ship proved impractical because of the expense"; "he is intelligent but too impractical for commercial work"; "an impractical solution"
In statistics, it is said that there is no practical significance. A test that has a statistically significant result does not necessarily have a practical significance. For more explanation of the term, you can read here
I'd say the water advice is "useless" and the practice of drinking water to lose weight I'd call "futile."
What about the word fatuous? From Dictionary.com:
fat·u·ous /ˈfætʃuəs/ (adj.)
1. foolish or inane, especially in an unconscious, complacent manner; silly.
2. unreal; illusory.
"Yes, I suppose your advice is technically correct, but it is utterly fatuous to think it important for my diet plan."
If you're ok with a phrase, things like this are often said to look good on paper:
to seem fine in theory, but not perhaps in practice; to appear to be a good plan. The plan looks good on paper, but it may not work. This looks good on paper. Let's hope it works in the real world.
"nugatory"? "vacuous"? "inutile"?
"inapplicable" would be the most direct adjective.
Ineffective.
Technically, the act of drinking water may indeed burn calories, but in reality it's completely ineffective as a weight-loss strategy.
How about purely theoretical, since the words theoretical and practical are often viewed as opposites.
