John is correct, at least for U.S. usage. It is a slightly joking or teasing expression. It's not a serious insult, but it suggests that the person is overenthusiastic. It is similar to the word "green."
And I, too, think the word is suggestive of "crunchy granola." The United States has been a very enthusiastic consumer of packaged, nationally-branded "breakfast cereal" like Kellogg's Corn Flakes. In the late 1960s and early 1970s people concerned with healthy eating, natural foods, and the counterculture would often suggest that instead of buying commercially packaged cereal, people ought to make their own granola at home. So "crunchy granola" became a kind of emblem of a certain lifestyle.
I hate to stereotype cities, but... Boulder, Colorado might be stereotyped as a "very crunchy" city.