Classifying A Distinct Form of Diabetes in Lean Individuals with a History of Undernutrition:An International Consensus Statement

Since 1955, a form of diabetes in lean young individuals with a history suggestive of undernutrition from before birth and through childhood has been described in the literature. In 1985, the World Health Organization formally classified it as “malnutrition-related diabetes mellitus” but subsequently removed it in 1999 over a disagreement as to whether undernutrition was a sufficient risk factor to cause this type of diabetes. Emerging evidence now strongly supports the distinct classification of this unique diabetes phenotype, which is characterised by significant impairment of pancreatic insulin secretion with normal hepatic and peripheral insulin sensitivity, as well as a lack of ketoacidosis and the absence of islet cell autoantibodies. In this consensus statement, we synthesise this evidence to produce a set of common features of the disease, proposed pathogenetic mechanisms, and suggested management and prevention strategies. During a recent Consensus meeting in Vellore, it was proposed that this distinct form of diabetes be given the nomenclature “Type 5 diabetes mellitus”, subsequently formalised at the International Diabetes Federation’s (IDF) World Diabetes Congress in April 2025. We call upon the international diabetes community to recognise this distinct form of diabetes and to support the IDF’s Type 5 Diabetes Working Group and its goals to promote more research into its phenotype, pathophysiology, and treatment for the benefit of millions of patients worldwide, particularly in low- and middle-income countries (LMICs)