Study finds lean and overweight forms of type 2 diabetes differ

Almost 10 million lean people with type 2 diabetes may be receiving care designed for a different form of the disease, according to researchers from Amsterdam UMC and the University of Ghana. Their analysis of more than 3,300 African adults found that lean and overweight patients often arrive at the same diagnosis by different biological routes.

For people with a higher body mass index (BMI), the main problem is insulin resistance: the body does not respond properly to insulin. For lean patients, the pancreas appears to fail to produce enough of the hormone. The distinction matters because both groups are generally given the same oral drugs, such as metformin or sulfonylureas, which are mainly effective against insulin resistance.

The complications also separate. Lean patients more often developed retinopathy, or diabetes-related eye damage, and strokes. Patients who were overweight more often had high blood pressure and a higher risk of cardiovascular disease. Chronic kidney disease appeared equally often in both groups. The researchers link the pattern to differences in body fat and risk factors: lean patients were more likely to have experienced malnutrition or low birth weight, which can disrupt pancreatic development.

And so what, concretely? A lean patient in Ghana, Nigeria, Kenya—or of African descent living in Europe—may need a treatment strategy that addresses insufficient insulin rather than primarily insulin resistance. The case is not confined to Africa: a separate UK Biobank analysis found that people of African descent had the same diabetes risk at a BMI of 26 as Europeans at a BMI of 30, while migrant studies found earlier onset and poorer blood-sugar control.

The findings come from a multi-cohort analysis published in Diabetologia, not from a trial showing that a different drug improves outcomes. Researchers Sabrina Esmail, Charles Agyemang and Felix Chilunga are calling for targeted clinical trials to determine the best treatment for lean patients; until those trials are run, the biological distinction is clearer than the clinical answer.