Focusing on whether lean insulin-resistant individuals have elevated cardiometabolic risk, this study demonstrates that later clinical impacts of insulin resistance in lean persons remain to be elucidated in longitudinal investigations.

• This research involved 2,341 (51.8% females) healthy 16–23-year-old individuals who were categorized as lean or overweight/obese; and insulin-sensitive or insulin-resistant, and were compared.

• In both genders, similar measures of obesity were shown by lean insulin-sensitive and insulin-resistant participants.

• More insulin-sensitivity was present in lean insulin-sensitive individuals vs their overweight/obese peers; similar insulin-sensitivity was observed in insulin-resistant groups.

• Lean insulin-resistant individuals exhibited an increased cardiometabolic risk.

• Factors independently linked with insulin resistance in both genders were C-reactive protein, leukocyte count, and glomerular filtration rate; those in males were uric acid, asymmetric dimethyl-arginine, and soluble vascular adhesion protein-1; those in females were soluble receptor for advanced glycation end-products.

• Standard risk markers ascertained phenotypes linked with low insulin sensitivity.