The most common form of diabetes, type 2, is often linked to obesity. And by contrast, experts say type 5 diabetes affects even those who are thin or slim and have suffered long-term undernutrition in childhood. Undernutrition is a type of malnutrition where your body does not receive enough energy and nutrients to help maintain health, often leading to conditions like low weight, stunting, and being underweight. "We call upon the international diabetes community to recognize this distinct form of the disease," researchers wrote in the Lancet Global Health journal. "This neglected entity likely affects the quality and length of life of millions of people worldwide," they added. "Diabetes is associated with an increasing public health burden across the world, and the number of people living with the disease is expected to increase markedly in low- and middle-income countries, which are facing a double burden of undernutrition and overnutrition," the report authors wrote. The global study, which was published in The Lancet Diabetes and Endocrinology, found more than 40 per cent of people with diabetes do not know that they have it. "Even though the growing burdens of obesity and population ageing are key risk factors for the increasing prevalence of type 2 diabetes, undernutrition also appears to contribute to the burden, since atypical forms of non-type-1 diabetes have been reported to occur in young, lean individuals with a life course history of undernutrition," researchers added. Doctors say type 5 diabetes is mostly seen in young adults under the age of 30 years in low- and middle-income countries like India. What are the signs and symptoms of type 5 diabetes? A few signs and symptoms of type 5 diabetes include:

• Increased thirst
• Frequent urination or peeing
• Excessive headache
• Blurred vision
• Fatigue and tiredness
• Slow-healing wounds and sores

Doctors say most people with type 5 diabetes have classic symptoms of undernutrition like weight loss and hunger, and due to this, the condition becomes difficult to recognise. What causes type 5 diabetes? Even though the research on the condition is ongoing, scientists think type 5 diabetes happens when chronic undernutrition prevents your pancreas from developing completely. And so, a lack of nutrients for a long time can affect many other body parts, including the pancreas - the organ that makes insulin, a hormone that's necessary to manage blood sugar levels. People with this type have a history of malnutrition in early childhood or during fetal development. Ways to diagnose type 5 diabetes To diagnose type 5 diabetes, the doctor would usually do a blood glucose test, which checks the level of sugar in your blood. People who have diabetes mostly have a result of over 200 mg/dL. In the US and other high-income countries, doctors also use other tests to identify the other type of diabetes, like A1C, urinalysis, and antibody tests. But since the access to these tests is a little less in low- and middle-income countries, experts say type 5 diabetes mostly gets misdiagnosed. A unique feature of Type 5 is that those who have it often do not have ketones in their urine at diagnosis.