Lean type 2 diabetes may be a different disease

Clinical takeaway: Retinopathy and stroke were more prevalent in lean patients with type 2 diabetes, while hypertension and 10-year cardiovascular risk ran higher with overweight or obesity. Screening priorities may deserve to shift accordingly. 

Type 2 diabetes in adults often defies the standard picture: many patients are lean, with low insulin levels and failing beta cells rather than insulin resistance. Guidelines nonetheless recommend starting nearly everyone on insulin-sensitizing agents such as metformin, raising a long-standing concern that lean patients are being treated for a disease process they do not have. 

Whether that mismatch is accompanied by divergent outcomes had never been examined. A first-of-its-kind cross-sectional comparison across two large African cohorts now supplies additional evidence. 

African adults with type 2 diabetes showed complication patterns that split along BMI lines in opposite directions. Lean patients, defined by a BMI below 25, showed a 36% higher prevalence of diabetic retinopathy and a 41% higher prevalence of stroke than patients who were overweight or obese. Impaired eyesight was 12% more common in lean patients as well. 

The heavier group carried the macrovascular burden instead: hypertension prevalence ran 23% higher and estimated 10-year cardiovascular disease risk 15% higher than among lean patients. Chronic kidney disease was the exception, with no difference between groups, a null the authors note may reflect microvascular and macrovascular kidney mechanisms offsetting each other. 

Lean patients had lower insulin levels, markedly reduced beta cell function and higher fasting glucose, the profile proposed for an insulin-deficient form of the disease. Body fat percentage accounted for most of the complication differences. The pattern is not unique to Africa: in Indian, Chinese and Japanese cohorts, insulin-deficient forms of type 2 diabetes have shown elevated retinopathy risk, while insulin-resistant forms tracked with kidney disease.

The analysis pooled individual-level data from two of the largest African diabetes cohorts, the Africa America Diabetes Mellitus study and the Research on Obesity and Diabetes among African Migrants study: 3,331 adults with type 2 diabetes in Ghana, Nigeria, Kenya and Ghanaian communities in Europe. Prevalence estimates in this cross-sectional comparison were adjusted for age, sex, education and diabetes treatment. Insulin and beta cell measures came only from participants not receiving insulin therapy. 

The authors are calling for randomized trials to identify the most effective diagnostic, screening and treatment strategies for lean type 2 diabetes, which affects roughly two-fifths of the 24 million Africans with the disease, a question they argue extends to patients of African descent everywhere. People of African descent in Europe and America develop the disease years earlier and often at a lower BMI than White populations. 

"So a considerable proportion of African patients in Europe have a lower BMI but are treated according to guidelines written for the form of the disease found in people who are overweight, and their control is demonstrably worse," said Charles Agyemang, project leader, Amsterdam UMC. "There is no reason to assume that the treatment mismatch we describe stops at the border." 

Source: Esmail S, et al. (2026 Aug 23) Diabetologia. Divergent complication patterns of type 2 diabetes in African individuals who are lean versus overweight or obese: a multi-cohort analysis