INS and Insulin resistance: Nevertheless, basal plasma leptin concentrations are significantly lower in insulin-sensitive than in insulin-resistant men (1.90 ± 0.4 vs. 4.35 ± 1.21 ng/ml, P < 0.05) of identical body fat composition [67] suggesting either that excess leptin may also lead to increases in insulin resistance independent of adiposity or that leptin production increases in insulin resistant men in response to unknown feedback mechanisms in an effort to ameliorate the insulin resistance.