First – let’s admit that there are several different types of diets that produce dramatic improvements in weight loss and diabetes. The vegan diet is one of them (and one which also reduces risk in most other diseases better than the others) – but it is by unquestionably by far the very best diet for the environment and the survival of the planet. High protein (high meat and/or dairy) diets are absolutely TERRIBLE for the environment and are not sustainable in any way. A vegetable diet will END world hunger because we DO have enough earth to grow enough vegetables for everyone and we definitely do NOT have enough earth for meat eaters even at current levels.
A ketogenic diet helps control blood sugar levels. It is excellent for managing type 2 diabetes, sometimes even leading to complete reversal of the disease. This has been proven in studies. It makes perfect sense since keto lowers blood-sugar levels, reduces the need of medications and reduces the potentially negative impact of high insulin levels.