Type 2 diabetes is the form of diabetes mellitus in which the body’s cells progressively lose their ability to respond to insulin — insulin resistance — while the pancreas gradually fails to compensate. Strongly linked to excess weight, inactivity, and diet, it typically develops in mid-life but is increasingly seen in younger people. High blood sugar damages blood vessels, nerves, eyes, and kidneys over years, often silently. The good news is that it is substantially preventable and sometimes reversible: weight loss, physical activity, and dietary change can restore sensitivity, with medicines added as needed. It accounts for around nine in ten diabetes cases worldwide, making it one of the great public-health challenges of diet and lifestyle.