When is being, or being around, a "health nut", annoying or overbearing?

DISCLAIMER: I am referring to social settings and social interactions in this question.

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When do you feel someone being very self-conscious about their health and fitness is "too much" to the point of discomfort or annoyance?

Be as detailed as you like, using personal examples or scenarios if you wish.
When is being, or being around, a "health nut", annoying or overbearing?
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