[passivate]

You're claiming variance in basal metabolic rate (for people with similar activity levels/lifestyles) is potentially significant, but also variance in digestive efficiency is negligible?

I don't know if either is false/true, but its interesting to consider. Maybe someone from that domain can shed some light. Happy to look at anything you or others link to.

[yupper32]

BMR variance is significant. It's like the core to any weight loss story.

What I'm trying to say is that trying to change your BMR through some diet is a fool's errand. Just figure out your BMR and consume fewer calories than that. It's very very simple (though I won't say it's easy).