I don't have the whole thing, I could see about getting it though.
The higher LBM, to me, simply means that more calories would have to be consumed for even minimum maintenance, which means more oxidation and metabolic byproducts for the organs to deal with.
Any fat or muscle that is not directly related to "survival" (whatever that means for the individual at the time, be it for warmth or strength or speed or whatever) will be detrimental to longevity in the long term. It makes sense to me.
As we live so much longer than our prime fertile years these days, the very muscle that may help us in mating (appearance or the ability to "out-compete") has a cost on the amount of years we live.