You look slim, but could be at risk of diabetes: Doctors explain why

For years, diabetes has commonly been associated with obesity, excess body weight and an unhealthy lifestyle. However, the assumption that only overweight or obese people are at risk of developing Type 2 diabetes does not tell the whole story. Across India, people who appear slim, maintain a normal body weight and may not show obvious signs of obesity are also being diagnosed with the condition.While this may seem like a growing trend, experts say it is not necessarily a new phenomenon. What has changed is the attention being given to it. Indians have long been known to develop diabetes at lower body mass index (BMI) levels than several other populations.The reason lies partly in how the body stores fat. A person may look thin on the outside but carry excess fat around internal organs, including the liver and pancreas. This hidden fat can affect how the body processes glucose, leading to insulin resistance and an increased risk of diabetes.According to Dr Ambrish Mithal, Group Chairman and Head of Endocrinology and Diabetology at Max Healthcare, the way obesity is traditionally measured needs to be reconsidered. BEING SLIM DOES NOT MEAN BEING METABOLICALLY HEALTHYConventionally, obesity has been defined using BMI, which measures body weight in relation to height. However, Dr Mithal said BMI is largely a measure of overall body weight and does not reveal where fat is stored.He explained that the metabolic impact of excess fat is largely determined by visceral fat, which accumulates in the abdomen and around internal organs. Fat deposited in organs such as the liver and pancreas can also directly affect their functioning. This fat is metabolically active and releases inflammatory substances called cytokines, which can damage blood vessels and interfere with pancreatic function."Weight alone is not a good criterion," Dr Mithal said, adding that waist circumference and waist-to-height ratio can provide a better understanding of central fat accumulation and metabolic health.He highlighted that waist measurements of 80 cm or more in women and 90 cm or more in men are important indicators of abdominal obesity among Indians.WHY INDIANS DEVELOP DIABETES AT A LOWER BMIIndians and other South Asians are more likely to develop metabolic abnormalities at lower body weights compared with several Western populations.Dr Mithal said this vulnerability may be linked to long-term nutritional patterns and what is known as the thrifty gene hypothesis. According to this hypothesis, generations of nutritional deprivation may have influenced how the body stores' energy.He explained that inadequate nutrition during pregnancy can affect how a foetus develops. When such individuals are later exposed to energy-dense foods and diets rich in refined carbohydrates, their bodies may be more likely to store excess energy as fat, particularly around internal organs.However, he stressed that the reasons are not completely understood and genetics also plays a role. There is no single identified gene that explains why Indians are particularly susceptible.An editorial published in the journal Diabetes and Metabolic Syndrome: Clinical Research and Reviews in February 2026 also highlighted the Asian Indian phenotype, characterised by higher body fat, normal or relatively low body weight and lower muscle mass. It pointed to abdominal fat and fat accumulation in organs as important contributors to metabolic risk.NOT ALL LEAN PEOPLE HAVE THE SAME TYPE OF DIABETESDr Mithal explained that there are different reasons why a person with a lean body type may develop diabetes.One involves excess abdominal fat and insulin resistance, where the body's cells do not respond effectively to insulin. Another involves problems with insulin secretion, caused by dysfunction of the pancreatic beta cells that produce insulin. Such individuals may develop Type 2 diabetes without necessarily being overweight.He also pointed to latent autoimmune diabetes in adults (LADA), a form of autoimmune diabetes that can develop later in life and may be seen in lean people.Therefore, not every slim person diagnosed with diabetes has the same underlying condition, making proper medical evaluation important.WHAT SLIM PEOPLE SHOULD WATCH OUT FORDr Anoop Misra, Chairman of Fortis C-DOC Centre of Excellence for Diabetes, Metabolic Diseases and Endocrinology, New Delhi, said Indians tend to have a higher proportion of body fat, particularly around the abdomen and internal organs, than Western populations with a similar BMI. Lower muscle mass can also affect glucose metabolism.He said people with a normal BMI should pay attention to increasing waist circumference, a family history of diabetes and a sedentary lifestyle. Other warning indicators include fatty liver, high triglycerides, low HDL cholesterol and increasing blood pressure.Early symptoms of diabetes can be subtle and may include persistent tiredness, fatigue, increased thirst, frequent urination, unexplained weight loss, blurred vision and delayed wound healing.Dr Misra recommended screening tests such as fasting blood glucose and HbA1c to identify diabetes or prediabetes. An oral glucose tolerance test (OGTT), which he described as the gold standard, can also be useful, particularly when suspicion remains despite a relatively normal HbA1c.The larger message from experts is that body weight alone cannot determine metabolic health. Even people who appear slim should pay attention to their waist measurements, family history and blood sugar levels. Looking healthy on the outside does not always mean the body is free from metabolic risks.- Ends