Human metabolism is complex and the body can adjust its efficiency with calories even with the same body mass.

“the human metabolism is extremely complex it's actually the second most complex thing that we know of in the universe i think the first thing is the brain the second thing would be mammalian metabolism and the metabolism does some pretty interesting things it's not as straightforward as i have this much lean body mass i have this much you know and therefore i burn this many calories your body can actually choose to become more or less efficient with calories of the same body mass that you have right”