A study published in the journal Diabetologia, conducted jointly by Amsterdam UMC and the University of Ghana, found that body mass index plays a role in shaping how type 2 diabetes develops, with two distinct disease pathways observed depending on where a patient falls on that scale. Among people with a lower body mass index, the pancreas produces insufficient insulin — a pattern the research contrasts with higher-BMI cases, where insulin resistance tends to be the dominant factor underlying type 2 diabetes.
Clinicians currently apply an identical pharmaceutical regimen to both patient populations, even though the underlying biological processes driving each condition differ. Research has long placed excess body weight at the centre of type 2 diabetes risk, shaping how the condition tends to be understood by both clinicians and the public.
Among higher-income nations, the data indicate a clear pattern: roughly nine of every ten people diagnosed with type 2 diabetes also carry excess body weight. Patterns vary considerably across the African continent. Roughly four out of every ten adults across Africa who carry a type 2 diabetes diagnosis maintain a normal or below-average body weight, and across certain rural communities — Ghana's among them — that proportion rises to roughly six out of every ten.
Lead author Sabrina Esmail noted that roughly ten million patients across the African continent who carry a lean body profile fall outside the conventional diagnostic picture. Charles Agyemang of Amsterdam UMC, who led the research team, noted that the findings point to a need for tailored therapeutic approaches for this sizeable population of lean individuals across Africa — a group in which an insufficient supply of insulin, rather than a diminished bodily response to it, appears to underlie the condition, yet one that is routinely placed on the same treatment pathway as others across the continent, receiving oral medications such as metformin or sulfonylureas in line with international guidelines.
Researchers note that this class of drugs addresses the body's reduced sensitivity to insulin rather than any deficit in the hormone's production. No examination of those consequences had taken place before this study.
Drawing on records from upwards of 3,300 adults living with type 2 diabetes across Ghana, Nigeria, Kenya, and several European countries, the team built its dataset from an African-majority pool of participants. Felix Chilunga, the research team's lead author, noted that the data indicated a pattern in which patients with lower body weight faced a higher likelihood of developing retinopathy — a form of eye damage — as well as strokes.
Elevated blood pressure and a heightened likelihood of cardiovascular disease are among the health conditions that research associates with carrying excess body weight. Rates of chronic kidney disease were comparable across both groups, and adipose tissue volume accounted for much of the observed variation — a pattern the data linked to distinct underlying pathological mechanisms rather than shared ones.
Two distinct risk profiles emerge from the data: excess body weight tends to accompany poor dietary and activity habits, while patients at the lower end of the weight spectrum are more frequently found to have a history of nutritional deprivation or low birth weight — both of which can interfere with normal pancreatic development. The research indicates that among lean African patients, the biological and clinical profile of type 2 diabetes diverges considerably from the condition observed in those carrying excess weight, yet treatment protocols have not kept pace with that distinction.
Chilunga called for focused clinical trials to establish which treatments prove most effective for this patient population, which she described as both large and frequently under-served by existing research. Separately, a UK Biobank analysis found that people of African descent living in Europe reach the same diabetes risk at a BMI of 26 as their European counterparts do at a BMI of 30.
Research conducted across European migrant populations indicates that people of sub-Saharan African descent face a notably higher likelihood of receiving a type 2 diabetes diagnosis, with onset tending to arrive roughly a decade earlier and glycaemic management proving harder to achieve than among longer-established residents. Agyemang noted that a notable share of African patients receiving care in Europe present with lower body-mass-index readings, yet their treatment follows protocols developed around an overweight patient profile — a mismatch that the data link to measurably poorer disease management outcomes.
The pattern of treatment disparity documented in the study is unlikely to end at any national boundary. The research is a multi-cohort study examining how health complications unfold differently among African patients with type 2 diabetes depending on whether those individuals carry lean versus overweight or obese body profiles. The study's findings are published in Diabetologia under the journal reference identifier 10.1007/s00125-026-06830-2.
