I don’t think it’s so much childhood (Type I) diabetes that is epidemic. Moreso, it is Type II - adult onset - which used to happen about age 40 or 50 for obese people; now happens at 20 or 30 for some.
One scientist I heard interviewed on the radio was working on the 30-second work-out. Sounds stupid, but basically - Type II is from the body having so much sugar in the system, it decides to strop processing it. Insulin stops working the way it should. They were experimenting to show that exercising for at least 30 seconds at top effort 3 times a week was as effective as anyting else in making insulin to do its job. This was enough effort (if you did 110%) to empty the stored energy in your muscles, allowing the insulin to recharge them.
My theory is that most “random” disease like Type I diabetes, heart attacks, alzheimers, Parkinsons, arthritis and such are virus-related. Unlike chronic conditions, they strike randomly at people for no specific reason - just like a virus. Other factors may contribute; but some obese people have no heart problems, some perfectly thin people get clogs. Your immune system may just decide to randomly attack your joints or your pancreas - or it may be in response to some minor infection we don’t know about.
Parkinsons often behaves just like a wasting disease - some cures like stem cells or fetal brain tissue relieve the symptoms for a while, then as that new tissue is destroyed too - the symptoms return just as strong.
When something just “flares up” it may be a recurrence of a dormant virus, much as cold sores or post-polio syndrome happen randomly.
See how much effort it took to just find the AIDS virus when they knew it was there in the 1980’s? We’re not even looking at this problem. Who remembers that until the 1990’s stomach ulcers were believed to be life-style induced, usually from chronic worrying? Today we acknowledge they are infections, and a simple drug will cure them.