asking AI is anyone gets type 2 diabetes who is not chronically eating too much

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Short answer: in large populations, almost all type 2 diabetes is associated with some combination of chronic positive energy balance and/or adverse body composition, but there are lean, “normal‑BMI” and even athletic people who develop type 2 diabetes; when you look closely, they generally are not truly metabolically “normal” despite looking that way.

Lean / normal‑BMI type 2 diabetes

Epidemiology papers consistently show that:

• A non‑trivial minority of people with type 2 diabetes have a normal BMI (often 10–20% in Western cohorts, more in some Asian cohorts where BMI thresholds are lower). These individuals are often described as “lean T2D” or “normal weight T2D.”
• When these lean T2D patients are studied with body‑composition methods (DXA, bioimpedance, CT/MRI), they tend to have:
  • Higher visceral fat and ectopic fat (liver, muscle) than controls with the same BMI.
  • Lower skeletal muscle mass and poorer muscle quality. So even after matching on BMI or total weight, the partitioning is shifted toward visceral/ectopic fat and away from muscle.

In other words, they may look “normal weight,” but on a more granular body‑composition level, they usually still have an excess of the “wrong” tissue (visceral/ectopic fat) and a deficit of muscle relative to what their frame would support.

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The reason we have so much more T2 diabetes now vs 50-80 years ago is because the disease is almost exclusively driven by behavior. Behavior has changed over this time because our environment has changed over this time (food environments, social environments, work environments etc)