Values are marginal means from a linear regression model including an interaction term between fat mass index and lean mass index, adjusted for confounders. Lean mass index was fixed at 11.4, 11.9, 12.4 and 13.1 kg/m2 and fat mass index was fixed at 2.9, 3.7, 4.6 and 5.8. These cut-off points are quintiles (i.e. values that divide the range of data into five equal parts).