We wish to thank Dr Nobili and Dr Targher for their comments concerning our recent paper (Gut 2007;56:1296–301), as this gives us the opportunity to clarify a few aspects of insulin sensitivity/resistance and the different physiological meanings of HOMA-R and OGIS. The euglycaemic hyperinsulinaemic glucose clamp measures insulin sensitivity (IS) as the ability of insulin to lower blood glucose levels by stimulating glucose uptake (mainly in the muscle). When comparing the clamp with other surrogate methods of IS, it is important to understand whether the index is based on similar principles, and correlation coefficients with the clamp are not sufficient to judge their validity.1

HOMA-R is calculated in the fasting state, thus reflecting the ability of basal insulin to suppress …