The secret is lots of veggies, fruits, and whole grains. The calorie density is low so it's easy to stay in a normal calorie range or even a deficit which is key for reducing risk of type 2 diabetes. Fat, especially Saturated fat causes insulin resistance. Many studied show this. Please show me any long term studies or a culture that are metabolically healthy on long term keto diets. Take a look at Virta health. Tons of money spent on low carb diets that achieved very little.
Try a book like "fiber fueled". That's a diet that is actually sustainable.
There is no "secret" here. While saturated fat might play some role in type-2 diabetes (there appears to be a genetic factor for some patients), the immediate cause of insulin resistance is excessive carbohydrate intake. The Virta Health approach of nutritional ketosis appears to be quite effective and sustainable for many patients.
Try a book like "fiber fueled". That's a diet that is actually sustainable.