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by DebtDeflation 405 days ago
>It’s ok to assume that you absorb 100% of what you eat

That's not really true. If you've ever done the keto diet, you know that your body expels unburned ketones through your breath, sweat, and urine. Protein can be used to repair structures rather than burned or stored for energy.

There's also something called the "thermic effect of feeding". Your body requires more energy to process protein (20-30% of calories consumed) than it does carbs (5-10%) than it does fats (0-3%).
1 comments
codingdave 405 days ago
> you know that your body expels unburned ketones

In other words, "calories out".

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anonymars 405 days ago
Great, but parent is responding to

> It’s ok to assume that you absorb 100% of what you eat

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ses1984 404 days ago
It didn’t get converted to ketones and expelled in your poop.

Your gut absorbed it. That is literally what digestive absorption is about. Expelling ketones is not digestive malabsorption.

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anonymars 403 days ago
There are many ways for food to not be 100% absorbed, which I think can most easily be demonstrated by eating a bag of nuts and waiting a day or two

I don't think it's unreasonable to think that different bodies absorb food in different ways (or proportions), particularly given what we've seen about the gut microbiome

Apparently even just changing the time of food intake can affect obesity (in rats) if this study is to be believed: https://pubmed.ncbi.nlm.nih.gov/22608008/

In response to, "but those are rats", I think it's a lot easier to cast doubt on "100% of food is always absorbed" vs "I don't think that always holds true"

I mean, heck: if there are no residual calories in human waste, how can it burn?

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ses1984 402 days ago
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?

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