[ses1984]

My original point: it's ok to assume you absorb 100%.

About the rat thing: the cico hypothesis point of view might look at whether meal timing affecting energy expenditure first, rather than assuming meal timing change digestive absorption.

There is not much point in getting in the weeds about how much you absorb, unless you're running trials on yourself like changing when you eat, or what you eat, and leaving all other things equal like calorie intake and expenditure.

The best dieting strategies I've seen track calories in and weight change. From their you derive calorie expenditure, and it really doesn't matter if you burned it or pooped it out, does it?