= 27d567bc2d48d9f40e9ccc20ea370b15)
RichardKennaway comments on How I Lost 100 Pounds Using TDT - Less Wrong
You are viewing a comment permalink. View the original post to see all comments and the full post content.
= 783df68a0f980790206b9ea87794c5b6)
Loading…= b715d02e85f7b3b4ae65ca3d3e450868)
Subscribe to RSS Feed
Powered by Reddit
= f037147d6e6c911a85753b9abdedda8d)
You are viewing a comment permalink. View the original post to see all comments and the full post content.
Comments (242)
I am not sure I am convinced by this argument, for the following reasons:
If you think of calorie content / thermodynamics as an upper bound on how much energy can be extracted from the food, you have to make an argument for what happens to the unused energy. Even if you are in a biochemical state where not all the energy is used, there is still energy floating around in your body in the form of carbohydrates, fat and protein. I can think of three possible mechanisms for what happens to this extra energy, and I am not convinced by any of them:
(1) Calories are excreted unused in their original form. However, I don't think this happens to a meaningful extent
(2) If there is excess fat, nutrients are broken down to molecular constituents in a less efficient mechanism of cellular metabolism, ie, producing less ATP. This is a little more plausible than 1, but I think it would be evolutionary maladaptive to reduce the fuel efficiency of your engine unless it was absolutely necessary. Note that there are cases when the body does reduce the fuel efficiency (such as anaerobic metabolism), but I can't see how this applies here
(3) (Added): If there is excess fat, the body begins to run processes that are not strictly necessary, thus using more fuel. However, I am not sure what these processes would be, or why they would be triggered by fat and not carbohydrates.
I find it plausible that increasing fat intake will help you lose weight due to regulatory pathways such as insulin, but I think this pathway operates almost exclusively through changes in appetite. I fail to see any arguments why we cannot use thermodynamics (calorie input/output) as a very good approximation of predicted weight change.
EDIT: This comment is being downvoted. I am happy to delete it if it doesn't add to the discussion, but it would help me immensely if someone could explain why my reasoning is wrong...
EDIT2: I am not sure if I misunderstand the karma system, but I don't think you are supposed to downvote someone for disagreeing with their conclusions. It is possible that I am wrong in my conclusions, but I don't think this in itself is reason for downvoting.
If you disagree with my arguments, you can dissect them in the comments. Reasonable arguments with incorrect conclusions are still valuable in a discussion, and if you show why they are wrong, you will not only help me update my priors, but also help reveal a flaw in how non-trolls come to their beliefs. Hiding the comment prevents this. I don't see any reason for downvoting, and I think the downvoters need to ask themselves if they are downvoting due to mood affiliation / cognitive bias.
(4) Calories are excreted unused not in their original form.
What do you think shit is made of? When dried out, it will burn -- that's calorific value right there. Everyone takes in more calories than they turn into heat and motion.
(5) Thermogenesis. If that's impaired, you won't burn as much fuel as it takes to maintain body temperature, but you may not even notice, because you'll do other things to keep warm instead. Come to think of it, accumulating an insulating layer of fat will also dampen the effect.
CICO is about as helpful as MIMO -- matter in, matter out. In is easy to measure, out not at all easy.
There is obviously thermodynamic energy in food which is not absorbed in the gastrointestinal tract. Fiber is an example of this. Energy which is not absorbed is not listed on the nutrition label of food. When I say 'calories', I mean the biochemically available energy in absorbed macronutrients such as fat, carbohydrates, protein and alcohol.
Nobody doubts that thermogenesis uses energy. This is a special case of my mechanism 3. It is part of the 'energy used'. Again, if you want to convince me that you can eat 3000 calories of fat without gaining weight, you would have to make an argument that the proportion of fat in my diet has a causal effect on thermogenesis, ie, that my body will start running additional thermogenesis because I ate fat instead of carbohydrates.
Your claim that CICO is as helpful as MIMO is clearly ridiculous, and if you truly believe this, then supermodels eating tissue paper are more rational than you, as their beliefs will lead to more accurate predictions.
The point I am trying to make is that our body is an efficient engine due to evolutionary pressure, that energy doesn't just disappear (if it did, we would observe large amounts of unmetabolized macronutrients in urine), and that even if CICO is not the whole picture, it explains a very large part of the variation in body weight observed in human populations
On a previous occasion when this topic came up, I posted this anecdote.
Now, as you might imagine, there were medical reasons for that episode. Or rather, there were concurrent medical events with no obvious connection: acute ulcerative colitis, a disease of the large intestine only. Most nutrition is extracted by the stomach and small intestine, which were unaffected. So what was going on there? What made my digestive system so inefficient for several years following the initial attack?
So there's a lot of room for variation in digestive efficiency.
(For those who know the last-resort treatment for ulcerative colitis, I'll just add that I recovered without surgery.)
What is more ridiculous about MIMO than CICO? Conservation of matter, can't argue with that.
You don't get to be a supermodel unless you can stay thin. Some people can, no-one doubts that, and some people just are, without taking any effort. And I'll take Eliezer's word that nothing has worked for him over anyone's assertion that because they can't see how something could happen, it doesn't happen. CICO is only one part of the picture, and its abundantly clear from experiences of dieting that it's of little explanatory value on its own, and of practical value to only a subset of people.
OK, I see the point. But multicellular life evolved as thermodynamic engines, not as fusion plants. Over billions of years, cells were surviving based on how efficiently they could extract thermodynamic energy from macronutrients, to power intracellular processes. This is what we are optimized for. If we had been able to use fusion power in our evolutionary past, MIMO would be a more appropriate level at which to draw your map.