I’ve seen people who have type II diabetes who have always been slender and active. It usually strikes them much later, say at 70. And there are people who take the wake-up call, and eat well and exercise and lose weight, but their type II doesn’t go away. They’re still better off with the healthier diet and exercise but they do have to take medication to prevent the vascular damage that will cause eye, kidney and heart disease.
Same is true with blood pressure - I eat healthy and exercise, am not overweight, but thanks to my mother’s genes - and she has always been slender and active - I had hypertension at 40, same as she did.