The more you earn the more diseases you get. is that true ?

In a recent article in BBC.com I saw the above map of global Cancer cases. Looks a lot like a map of global GDP ! Look how Kenya is higher than its neighbors as is South Africa. See South Korea or tiny Singapore ? Israel is higher than its neighbors and Egypt higher than most of its !
My theory is : the more developed an economy, the more people are eating processed foods, or foods from a box. In poor countries people eat natural food, they cannot afford food which comes in a box, or fast food, or microwaves.
So my advice to you : eat natural foods. Avoid eating things that come in a box or a can. Avoid fast food. The cheapest food for lunch is not a good choice ! 
Similarly for my diabetic friends : eat natural and unprocessed foods. It will go a long way in helping you. The diabetics are usually the rich too!