Superfoods are a popular modern myth. Individually the reality is that these things make little difference. Eat a reasonable quantity of balanced diet with plenty of fibre, and take regular exercise, and you can't go far wrong. Don't do that, and adding a handful of "superfoods" to your diet won't make much difference.

Pacific islanders are the fattest people on the planet, and they eat lots of coconut, pineapple and fish. Chilli (it isn't specifically jalapenos) is eaten in especially large quantities in places such as India and West Africa and Mexico, where there is a growing obesity problem, despite them usually being thought of as food-poor regions of the world. If these people were recently thin, it is because they didn't have a lot to eat or did a lot of manual labour. Argentineans, once rather svelte, are rapidly becoming much fatter at the same time that their prodigious consumption of meat is falling - though those two things are probably not closely related.