It is defined as a decrease in resting energy expenditure during calorie restriction, beyond what can be explained by reduced mass of muscles, organs and fat. (alivebynature.com)
There's not much empirical weight behind the ban, although experts say it could reduce mass shooting deaths. (vox.com)
If you are hardcore and want to reduce mass then you could replace the heavy front seats with light weight ones and remove the rear seats. (evo.co.uk)