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What are the Lean indices on my DEXA report?

On the front page of your Bodyscan report is a small table titled Lean Indices. There are two indices based on your lean mass here:

1.    Lean mass/height-squared  – Lean Mass Index (LMI)
2.    Appendicular lean/height-squared – Appendicular Lean Mass Index (ALMI)

First of all, lean mass on your Bodyscan DEXA report means all lean tissue, or all soft tissue that’s not fat. Thus it includes internal organs but does not include bone. (Lean+BMC is lean plus bone, ie everything that’s not fat.)

Whilst your lean indices are not just about muscle, they give us a good indication about muscle mass and how it’s distributed.

Your LMI relates to all the lean tissue in your whole body, while your ALMI is just about the lean in your limbs (your arms and legs).

A simple way to make sense of how high or low your lean indices are is to check your percentiles in the ‘AM’ column to see how you compare to a population of the same age and sex. An AM percentile above 50 means that you have a higher lean index than most people your age and sex. A bodybuilder will typically have AM percentiles in the 90s (ie, an indication of more lean mass than just about everyone his/her age).

If the AM percentiles for LMI and ALMI are close together then it suggests that lean mass (and therefore muscle mass) is evenly distributed around the body. If they’re far apart (eg, an AM percentile of 50 for LMI, and an AM percentile of 75 for ALMI), this suggest that the muscles in the trunk are less well developed than in the arms and legs. It’s like scoring 75% in a French (limbs) exam but only 50% in a French & German (limbs + trunk) exam.  Clearly, your German (trunk) is dragging you down. So go and work on that German trunk!