Metabolic syndrome diagnostic criteria do not identify subclinical insulin resistance in individuals with obesity, as metabolically healthy obese individuals exhibit impaired insulin sensitivity despite lacking the full complement of metabolic syndrome components.

When fat cells become overloaded with fat, they release excess fatty acids into the blood. These fatty acids build up in muscle and liver cells, where they interfere with insulin's ability to signal the cells to take up sugar from the blood. This causes sugar to stay high in the blood even when insulin levels are normal, but standard blood tests miss this problem because other markers like blood pressure and cholesterol remain normal.