Figure 1. LOESS of annualized change in BMD versus average level of insulin resistance.

For each midlife stage (premenopause, the MT, and postmenopause), we used LOESS to visualize the relation between annualized change in LS or FN BMD (g/cm² per year) versus the average log₂HOMA-IR. Annualized change in BMD was calculated as the difference between the last and first BMD values in a midlife stage divided by the number of intervening years. Thus, a more positive rate of change indicates slower BMD loss, and a more negative rate indicates faster BMD loss. Here, we show the LOESS plot for rate of change in LS BMD versus the average log₂HOMA-IR level in premenopause. LOESS plots for the FN and the other midlife stages (menopause transition, postmenopause) were similar. Note the biphasic relation: when log₂HOMA-IR was less than 1.5 (raw HOMA-IR = 2.82), greater log₂HOMA-IR correlated with a more positive rate of change in BMD (slower bone loss); when log₂HOMA-IR was greater than or equal to 1.5, greater log₂HOMA-IR correlated with a more negative rate of change in BMD (faster bone loss).