For about $100 you can have your metabolism measured by a breathing device. Some places do 2 tests for $140 or something like that.
You can test yourself before and after, and then month or two later to see lasting effects.
Cole mentions that in order to afford eating more volume of food which would avoid slowing the metabolism, it is necessary to stay active during all day (snake walk, standing, moving). He doesn’t mean go to the gym for 1 hour and then sit all day, he means avoiding sitting as much as possible or increase walking time progressively until you can make a routine.