I think you're referring to 'Blue zones'[0] here. I'm certainly not an expert in longevity, but was also intrigued by these areas and their apparently above-average lifespan, and how it goes against a lot of conventional longevity advice re: diet.
One explanation I've heard is that they're simply the results of poor record keeping, and that there isn't much strong evidence to suggest people in those regions do statistically live longer than average.