Polynesian Obesity: Who's to Blame?

I was watching an episode of The Food Truck which involves Michael Van De Elzen roaming across New Zealand in his eponymous food truck attempting to get Kiwis to eat healthier versions of their favourite meals. Sometimes it's baked, not fried, chicken or soy bean falafels but in this particular instance the cuisine in question was Polynesian.
A brief look into their diet wasn't promising; one instance included a stew consisting of lamb flaps (breast/belly tissue with a high fat content) cooked in onions and ginger. Another involved a Polynesian individual describing the cultures' general disdain for vegetables and a man who simply stated that the food he made "doesn't have enough salt".
This wasn't the first time I had seen this; in the TV show The World's... and Me Mark Dolan made a visit to a Tongan family and their diets were very similar. Large feasts were a daily occurrence, supermarkets were stacked with cheap and fatty meat. Mark Dolan himself was introduced to the country with a popular breakfast item: a loaf of bread, hollowed out and filled with ice cream and a can of Fanta. Delicious.
Recent studies have shown that obesity in Polynesian countries is becoming a rampant problem; this source reveals some startling figures on the percentage of overweight individuals on those islands:

Western Samoa      -   Male: 33.3%   Female: 46.1%
Manu'a                    -   Male: 56.2%   Female: 76.9%
Tutuila                     -   Male: 61.9%   Female: 79.4%
Hawaii                     -   Male: 75.2%   Female:  80%

Clearly these offshore countries have become a casualty of western influence, but who precisely is to blame? The finger is initially pointed at the people themselves; naturally stocky folks who obviously have unhealthy food habits. However studies made in the 1960s (before major trading took place between neighbouring countries) show that their diets were generally well balanced, consisting of fruits, seafood and coconuts which provided the only high fat content.
The World's... and Me suggests that import products are to blame; Australia and New Zealand offload the fattier cuts of meat that are undesirable in western culture onto the Polynesian countries who, without realising the consequences, are happy to accept the surplus they've never had before. Annex to that the unusually high salt content of tinned products, destined for long shelf lives and many hours in transport, it's not hard to understand the earlier quip about the food not having enough salt; as a man in his thirties that flavour wasn't what he grew up with; it wasn't Polynesian.
Though I generally loath ignorance to responsibility, in this case I find myself siding with the afflicted. As untouched microcosms of traditional lifestyles it is unsurprising that they have been corrupted by the sudden influx of goods from more bountiful countries. They didn't look a gift horse in the mouth; unfortunately they ended up eating it.