My layman observation from tons of pop sci consumption is that the rate of metabolism seems to correlate greatly with life expectancy. Running at 100% all the time would likely wear the system out much sooner, e.g. due to higher oxidation and increased cancer risk.
Even if you are correct, the article discusses more efficient thinking as a goal.
If you have to floor the gas to make it out of your driveway, versus owning a well-tuned highly efficient modern car, those are two very different sorts of "metabolism".
