Link: https://www.amsterdamumc.org/en/research/news/study-indicates-type-2-diabetes-operates-differently-across-weight-profiles

Research published today reveals that type 2 diabetes manifests in two fundamentally different ways depending on a patient's body mass index (BMI). While type 2 diabetes in patients with a higher BMI is primarily driven by insulin resistance, the study demonstrates that in individuals within a lower BMI range, the condition is caused by the pancreas failing to produce sufficient insulin. Despite these opposing biological mechanisms, medical professionals currently treat both groups with the exact same medications.

TLDR: Fat people T2 is insulin resistance - the body is too full of glucose and can't use all the sugar it has. Lose all the weight to reverse it. Skinny people T2 is a growth problem - low birth weight and malnutrition leads to a pancreas undersized for adult insulin production - the body could use a lot more sugar, but it can't use the sugar because it doesn't make enough insulin to tell the body to use it. Africans are a higher risk group because of this.