Lean muscle mass is kinda like cholesterol particle information. It is where the truth beyond BMI is most likely to be found. That BMI abjectly fails to account for the % of lean muscle mass contributing to the measured weight of any individual - hence the Rock is morbidly obese (who’s brave enough to tell him?!) is a major flaw. Lean mass and fat tissue have very different metabolic properties so why would researchers disregard that fact?
This 2013 study clearly demonstrates clearly the link between skeletal muscle mass and all cause mortality in older folks.
That then links in neatly with another elephant in the retirement village - mobility. This study shows that the ability to sit down and literally pick oneself up again off the ground with ease correlates with long term mortality risk (adjusted for BMI and additional factors) after the age of 50. It's a great test by the way - try it.
The human is capable of remaining lean and strong for the duration of lifespan. Combining High Intensity Exercise with Low Grade Mobility (walking, swimming, yoga, pilates) can absolutely retain cardiovascular fitness, functionality and power as we age. Throw in a whole foods diet high in naturally occurring fats and you are set up for an assault on the Longevity Leaderboard.
Lean, Strong and Metabolically Healthy will always win the day.
Watch the "Run on Fat" movie trailer here