If it is type 1, lifestyle will not prevent
it (though of course
it is very helpful to manage
it). If
it is type 2, then lifestyle will help, but will not cure it and it does tend to progress over time.
Given your current situation, you should be tested for adult onset type 1 (sometimes referred to as LADA). this means blood test for c-peptide along with fasting blood sugar, and antibody tests.
If it is adult onset type 1, then the appropriate treatment is insulin rather than oral meds.