Processed foods are in simple form so easily digested and goes into the blood directly or quickly thus causing lot of sugar in blood.
If person exercise or do hard work it gets used up but people are not exercising enough to use up.
If there is lot of sugar insulin produces more and converts to fat and stores in the body as fat. so insulin is used more to store up the fat. For regular people without sugar this is balanced and person put on weight.
Pancrease when we are young produces not normal 40 but 60 units of insulin. but if we continue that way then pancrease gives up and person looses contol and person becomes diabetic.
For diabetic people the mechanism is not in control so if they eat more sugar insulin in not produce and more sugar is in blood.
If we eat that food once a while or parties that is okay but regular eating the pancreas gives up
example: pot of water we used 1/2 pot to drink and lets say we went to trip and come after 10 days there is no other water do you still use the same water kept for 10 days? we dont drink because it is stored for long time. But how about processed food which are kept for more than days. The foods used germs killing agents or pesticides etc to keep them safe