In regards to Diabetes, you must distinguish between Type 1 and Type 2 Diabetes. Yes, Type 2 Diabetes is a result of a bad diet and can often be fixed by a diet change.

However, Type 1 Diabetes is an auto-immune disease where one's own body is attacking its own pancreas. This can't be resolved by eating better. In fact, infants under the age of 1 are coming down with Type 2 Diabetes after their Vaccinations. Vaccinations are probably the major cause of increase in Type 2 Diabetes.

See my article about it here:
https://steemit.com/vaccines/@canadian-coconut/diabetes-in-infants-caused-by-vaccination-vaxxed-stories-from-the-road

If there is a cure for Type 1 Diabetes, is would involved reversing auto-immunity, where the body can learn to stop attacking its own organs. Hopefully such a cure exists somewhere, but I don't know what it is.