If it is diabetes type 2, diet really makes sense and I would even say that it is mandatory, just like changing your lifestyle in general. It is a completely different thing when it is diabetes type 1, which does not appear because of obesity or eating too much sugar. A good resource on diabetes type 1 I consider Breakthrough T1D, where there are articles that are actually informative and not just generic, and there is an option to sign up for clinical trials and in general stay aware of what diabetes type 1 is if you are dealing with it.