Well somewhat that depends on what type. Type 1 is autoimmune and people pretend we can’t affect that but the incidence keeps climbing.  Definition is lack of insulin.

Inflammation is a first step in immunity and many people are constantly inflamed either from their diet producing elevated insulin levels without drugs insulin resistance or autoimmune conditions they already have.

Type 2 is elevated insulin with insulin resistance.  Largely it is induced by diet.  Carbs raise insulin the most so need to be restricted and how often one eats is also a factor, grazing or snacking constantly is how to end up diabetic.  

intermittent fasting is thus also an aid.

mow there are genetic diabetics called Modi,  often, even usually misdiagnosed.  Many want to say it is always genetics but most of the time it is because families eat similarly.

Exercise that builds muscle is also helpful in preventing diabetes.