Individuals with metabolically healthy obesity exhibit insulin sensitivity levels that are intermediate between those of lean healthy individuals and those with metabolically unhealthy obesity, indicating that insulin resistance exists on a continuous spectrum across the obesity spectrum rather than as a binary condition defined by metabolic syndrome criteria.

When fat cells become full, they spill fat into other organs like the liver and muscles. This extra fat interferes with how insulin works in those tissues, making them less able to take up sugar from the blood. The more fat that builds up outside fat cells, the worse insulin works, creating a gradient of insulin resistance that matches how much extra fat the body stores.