Identified now: The diabetes type that is most lethal for Indians

For years, type 2 diabetes has largely been treated as a single disease driven mainly by obesity and insulin resistance. But a landmark Indian study has now delivered a stark warning: not all type 2 diabetes is the same – and some forms are far more lethal than others.

The study, published in the American Diabetes Association's journal Diabetes Care, found that Indians with insulin-deficient diabetes faced the highest risk of dying, including from heart disease. Researchers say the findings could fundamentally change the way diabetes is diagnosed and treated in India and across South Asia.

The study was carried out by researchers from the Madras Diabetes Research Foundation (MDRF), the Centre for Chronic Disease Control, All India Institute of Medical Sciences (AIIMS), Delhi and Emory University in the US.

“This is hugely significant,” said Dr K M Venkat Narayan, one of the senior researchers associated with the work and executive director, Emory Global Diabetes Research Centre.

THREE DIABETES TYPES

The researchers analysed 2,639 Indian adults with type 2 diabetes, which is driven by lifestyle and familial history reasons, unlike autoimmune type 1 diabetes, and nearly 5,000 people with prediabetes over a median follow-up period of more than 10 years.

What they found challenges long-held assumptions about the disease.

Instead of one broad category, type 2 diabetes in Indians split into three distinct subtypes.

The first, called severe insulin-deficient diabetes (SIDD), accounted for 23 percent of patients. These individuals developed diabetes earlier, had very high blood sugar levels, marked failure of insulin-producing cells in the pancreas, and required the highest use of glucose-lowering medicines.

The second group, mild insulin-deficient diabetes (MIDD), made up more than half of all patients -54.5 percent. They were generally leaner, had lower body mass index levels, and showed milder but clear insulin deficiency.

The third subtype, severe insulin-resistant diabetes (SIRD), represented 22.5 percent of patients. This was the more “classical” form linked with obesity and resistance to insulin action.

The findings showed that nearly 78 percent of Indians with type 2 diabetes had some degree of insulin deficiency – a striking contrast to the long-standing belief that insulin resistance is the dominant problem.

Researchers also identified two kinds of prediabetes. About two-thirds had insulin-deficient prediabetes, while one-third had insulin-resistant prediabetes.

HIGHEST DEATH RISK

The most alarming finding was the sharply different risk of death across these groups.

Patients with severe insulin-deficient diabetes had the highest risk of dying from any cause – more than three times higher than people with normal blood sugar levels. They also showed the greatest risk of cardiovascular deaths.

Even more worrying was the impact on lifespan.

People with severe insulin-deficient diabetes lost an estimated 17.7 years of life. Those with mild insulin-deficient diabetes lost 12.8 years, while severe insulin-resistant diabetes was linked with 12 years of life lost.

Among people with prediabetes, the insulin-deficient form also carried a significantly higher risk of death and heart disease, while the insulin-resistant form did not show the same danger.

In total, the study recorded 1,076 deaths during follow-up, including 405 from cardiovascular disease. Researchers say the results underline that insulin deficiency is not a minor feature of diabetes in Indians – it may actually define the most dangerous forms of the disease.

BEYOND OBESITY LINK

For decades, diabetes research globally has focused heavily on insulin resistance – where the body stops responding properly to insulin. Excess weight and obesity were seen as the central drivers.

But researchers say the new evidence reveals a different reality in South Asians.

“We are showing that a large proportion of people in India develop diabetes not just because of body weight, but because of insulin deficiency,” said diabetologist-researcher Dr Anjana Mohan, co-author of the study who is also president, MDRF.

She noted that earlier work had already shown insulin-deficient patients faced higher risks of diabetic eye disease and kidney disease. The new study now links the same subtype to excess mortality. “This starts early, causes lean-onset diabetes, and can lead to excess mortality,” she said.

The study also challenges the stereotype that only overweight individuals are at high risk.

Many Indians with the insulin-deficient forms were relatively lean but still developed severe disease because their pancreas could not produce enough insulin. Experts say this may explain why many Indians develop diabetes at younger ages and have lower body weights compared with Western populations.

RETHINKING TREATMENT

Scientists say the findings could have major implications for diabetes care in India, home to more than 10.1 crore people with the disease, and another 13.6 crore with prediabetes.

Current treatment approaches often assume insulin resistance is the main problem. But if insulin deficiency is driving disease in most Indian patients, doctors may need to diagnose subtypes earlier and tailor treatment differently.

The pancreas, liver, muscles and fat tissue all play a role in diabetes. Inflammation and fat accumulation can interfere with insulin action, while persistently high sugar and fat levels gradually damage insulin-producing cells in the pancreas.

Researchers believe identifying high-risk subtypes early could help prevent complications and premature deaths. The study also highlights the importance of screening people who may appear thin or only mildly overweight but could still carry dangerous metabolic risks.

Experts say the findings may eventually push diabetes care toward a more personalised model rather than a one-size-fits-all approach.