Lean body mass is not beneficial, but may be detrimental for glucose tolerance - Splitting body mass index according to body composition.

Aims: To study the combined effect of lean mass index (LMI) and fat mass index (FMI) on glucose regulation based upon findings in an oral glucose tolerance test (OGTT) and homeostasis model assessment of insulin resistance (HOMA-IR).

Methods: We conducted a population-based, cross-sectional study including 1617 participants without diabetes born in Helsinki from 1934 through 1944. LMI and FMI were calculated as lean and fat mass (kg)/height (m).