Should Type 5 diabetes be a category at all? Top diabetologists question lack of evidence, data

Indian Express

10-06-2025

Top endocrinologists have questioned the way Malnutrition-Related Diabetes Mellitus (MRDM) has been hastily rechristened as Type 5 diabetes by the International Diabetes Federation (IDF).
In an expert review, Dr Anoop Misra (chairman, Fortis C-DOC Hospital for Diabetes and Allied Sciences), Dr Ambrish Mithal (chairman, Endocrinology and Diabetes at Max Healthcare) and Dr Shashank Joshi (diabetologist, Lilavati Hospital, Mumbai) have argued that the new classification runs ahead without robust modern evidence or clearly defined diagnostic criteria. Their critical analysis was published in Diabetes & Metabolic Syndrome: Clinical Research & Reviews recently. 'Reclassifying MRDM as Type 5 diabetes is premature and not supported by current evidence,' they wrote.
They argue that MRDM, though first recognised in 1985, was declassified in 1999 due to poor evidence. They say the same holds true today as overlapping symptoms continue to be misleading, the body mass index (BMI) criteria are considered outdated and there is not enough data to warrant a separate type of diabetes. 'We still need rigorous research and definitive biomarkers for such a classification. Besides, there has to be a global consensus,' says Dr Misra. Excerpts:
Why can't MRDM be classified as Type 5 diabetes?
There's no conclusive evidence that MRDM is a distinct disease rather than a variant or complication of existing diabetes types. Only a distinct phenotype (traits which define the 'what' of a disease) with robust data different from established types merits new classification.
MRDM overlaps with other types of diabetes — type 1 (due to autoimmune markers in some cases), type 2 (with insulin resistance or secretory defects), and secondary diabetes (when the pancreas doesn't produce enough digestive enzymes).
There's inadequate evidence. Only a few, small-scale studies, such as the 2022 study by Lontchi-Yimagou, exist. Rest are 25-40 year old data, some of which is mostly clinical. These studies are largely cross-sectional and limited in scope, sample size and generalizability. The American Diabetes Association (ADA) and WHO have never formally acknowledged type 3 or type 4 diabetes, making the proposal of a 'type 5' both arbitrary, confusing and unacceptable.
What's needed for a classification?
A valid classification demands a clearly distinct cause or causes, well-defined diagnostic criteria, international consensus and therapeutic utility. MRDM does not currently satisfy these requirements.
Did MRDM ever receive the attention it deserved?
The WHO classified it as a separate category in 1985 and it was discussed in international diabetes forums such as the 1976 IDF Congress. However, this attention waned due to the poor quality and limited quantity of research, which was largely descriptive and observational. Eventually, the WHO removed MRDM from its classification in 1999, citing insufficient evidence. In India, MRDM has become increasingly rare. Many experts report not encountering it at all, suggesting its relevance has significantly declined.
Should MRDM be treated as a type or a subset of diabetes?
MRDM is best viewed not as a separate type of diabetes but as a subset or modified form of existing types, most likely falling under secondary diabetes or as a variant of type 1 or type 2 diabetes. This type is influenced by factors such as chronic undernutrition. Defining it as a distinct 'type' risks oversimplification and could introduce unnecessary confusion in diagnosis and management.
What is the classification's impact in India?
India historically played a major role in defining and reporting MRDM, contributing to a significant volume of early literature. But MRDM was also reported from many other tropical countries. However, current data reveal a steep decline in the prevalence of undernutrition (proxy by BMI). For instance, thinness among women aged 20–54 dropped from 31.7% in 1999 to 14.2% in 2021.
Moreover, many individuals with low BMI in India are constitutionally thin and not necessarily malnourished or unhealthy. Reintroducing MRDM as a major category today risks diverting clinical attention and public health resources away from the pressing and widespread problem of type 2 diabetes, which remains the dominant and surging diabetes burden in India.
What more evidence is needed?
We need large-scale, prospective cohort studies with long-term follow-up; detailed nutritional, immunological and metabolic profiling; insulin secretion and sensitivity assessments using gold-standard methods; standardized malnutrition definitions; and comprehensive genetic research. Without this evidence base, the proposal to reclassify MRDM is premature, unsubstantiated and unacceptable.
How does Type 5 classification hamper treatment protocol?
Classifying MRDM as 'Type 5 diabetes' may introduce more confusion than clarity. It suggests a degree of diagnostic and therapeutic precision that does not exist. Moreover, such a label does not provide actionable clinical guidance, as patients show variable insulin needs and mixed autoimmune markers. It could also mislead policymakers and healthcare providers, diverting attention and funding from more prevalent and well-characterized diabetes forms such as type 2.