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Wait. What did that really say?

July 30, 2012

On Facebook today, my attention was directed to this article on The Huffington Post: “What is Metabolism:  How Long After I Eat is Weight Added to My Body?An anonymous reader wanted to know the answer to this.

Now, the reason it even pinged my consciousness was that the person who added the link to their Facebook wall said it takes about 12 hours. My first thought was, “Really?  They are now saying you can gain weight 12 hours after you’ve (over)eaten? I want to see the study that they gleaned that little gem from.

The thing is, that’s not (exactly) what the article is saying.

The author spends most of her time talking about how long it takes a piece of food to go through your body. However, this is where it starts to become confusing:

“We have a pretty good indication about the timeline from the sequence of ingestion, digestion, and egestion. The whole thing plays out over a span of roughly 12 hours on average,” says Dr. David Katz, a HuffPost Healthy Living contributor and director of the Yale University Prevention Research Center. “By the time the residual waste of food is passing out of us, the useable parts have all been put to use — for energy expenditure, as heat generation, or placed into storage, as either glycogen [from carbohydrate], or fat.”

So, 12 hours for the whole process.  Wait, that doesn’t seem correct.  From anecdotal views, as well as learning from people with food allergies, it seems the “residual waste of food passing out” doesn’t start, and especially doesn’t finish, in just 12 hours.

Ah, from the same article, a different number:

Putting it as delicately as possible, Mayo Clinic gastroenterologist Dr. Michael F. Picco writes: “Elimination of undigested food residue through the large intestine usually begins after a total of 24 hours. Complete elimination from the body may take several days.”

So, which is it? Is it 12 hours or 24 hours to several days?

Now, if one stopped reading there, especially at the first part I quoted, one could surmise that it takes 12 hours for too much food to turn into fat.

But wait!  Here, at the very bottom of the article it states:

“While the question posed seems extraordinarily simple, I don’t think that there can be a simple answer to it,” says Dr. Kaveh Ashrafi, an associate professor of physiology at the University of California, San Francisco School of Medicine who studies fat metabolism. “The prevailing view essentially considers feeding behavior/exercise as the sole determinants of body weight. For this to be true, one has to assume that the body itself is simply an inert vessel; if you put more food in it, it must get fat, if you move it, it must lose weight.”

Ashrafi offers this analogy in communication with HuffPost Healthy Living:

If one lives in a shack with broken windows, no insulation, and a caved-in roof, changes in the temperature outside correlate fairly well with changes in the temperature inside of the shack. However, if one lives in a modern home, with wonderful walls, windows, roof, and a sophisticated heating/cooling system, the relationship between the outside and inside temperate becomes much more difficult to guess easily. If the thermostat is set at 70°C, it can be -20 or +120 outside yet inside will be around 70. Body weight regulation is much more like the temperature regulation of the modern house than that of the shack — the prevailing view, in my opinion, treats it as if it were a shack.

So while it is easy to say how long it takes for your body to digest food, it is very difficult to answer the question, how quickly does it add weight to my body? That’s a very individual phenomenon, based not only on the make-up of someone’s diet, but on their unique hormonal and physiologic response.

So, how long does it take?  The true answer is we don’t know. Just like we don’t know why some people eat very little and are overweight or obese, and why others can eat a lot all the time, and never gain weight. There are too many individual variables to identify, much less measure consistently, between different individual bodies.

The way this article is written, especially in this “sound bite” world, people are going to see that and unequivocally say (as the person on my friends list did on his wall) that it takes 12 hours for that food you (over)ate to become fat. And we wonder where people get their information from anymore.

It seems that we don’t even have to have misreported or twisted “studies” proving to the world that us fatties are just lazy gluttons. Now, even when an article states that there’s much more to it than “calories in, calories out,” people are still going to read into it what they want.

9 Comments leave one →
  1. vesta44 permalink
    July 30, 2012 9:54 am

    Anyone who has eaten corn (or anything else that doesn’t get fully digested) can tell you that it can take a lot longer than 12 hours for food to go completely through one’s system, and that’s if one’s digestive system hasn’t been mutilated by WLS. If you have a mutilated digestive system, food can go through your digestive much faster than that, and you can still gain weight (been there done that). So how do they explain that away? If they think we’re overeating in that type of situation, they’ve never had to deal with anything remotely like it and don’t understand that eating a meal and then having to hit the bathroom within half an hour (or shit your pants) is not conducive to good nutrition or gaining weight from overeating – it’s actually a better motive to keep people from eating at all.

  2. Kala permalink
    July 30, 2012 10:37 am

    I’m honestly not really getting the outrage here. It doesn’t seem particularly unreasonable that excess food to fat could occur after 12 hours. It does take 24+ hours from ingestion to egestion, yes. But half or more of that time is when the food matter is in the colon. At that point, all that is reclaimed from the waste is micronutritents and water. All of the macronutrients are absorbed in the small intestines, directly into the blood stream. If those nutrients are in excess, they will be stored. The major form of storage are the fats in adipose tissue, with secondary storage in the form of glycogen in the liver. Now, in a more
    primitive eating situation, one where someone isn’t eating multiple meals in a day, you have a food boom and bust sort of thing where there’s no net weight gain. But for someone who is eating regularly and then overeats, I would think that ingestion to storage happens pretty quickly, as extra nutrients can’t just go around floating about the body in blood.

    I understand that everyone has a different metabolic set point that gives them a baseline size that their body wants to be at. For many people, that baseline doesn’t seem like it is necessarily thin. But at the same time, overeating for many people absolutely does cause weight gain. Simply because some thin people eat whatever and whenever and don’t gain weight, doesn’t speak to the vast majority of people who do gain weight when they overeat. That’s not to say that they all gain weight at the same rate, but most people certainly do. That’s not a moralistic statement, it’s simply an observation.

    • vesta44 permalink
      July 30, 2012 11:20 am

      But it doesn’t explain people like me, who have a mutilated digestive system, can’t eat very much or a wide variety of foods or foods that are considered “fattening” and still managed to get and stay fat in spite of of those facts. If it was simply a matter of how fast the food is digested, utilized, and stored, people like me would be thin, not fat. TMI WarningBecause I can guarantee you that when you eat a meal and then you’re in the bathroom shitting that same meal out within the hour (and it basically looks the same coming out as it did going in), you aren’t getting much nutrition out of that meal, nor are you storing much of that meal as fat.
      It also doesn’t explain the vast majority of fat people who didn’t get fat from overeating, of which I was one before I had my WLS. Before I had my WLS, I was an active person who ate between 1800 and 2100 calories a day except when I was dieting (which explains how I got fat – rebound weight gain will do it nearly every time). If overeating was the sole reason people got fat, then every thin person I know who has been able to eat like a pig for their whole lives should also be fat and that’s just not the case. Where do their “extra” calories go if they aren’t stored as fat? Because they aren’t exercising like hamsters on speed to get rid of them.
      The outrage is because this is a very complicated issue and people will read an article like the one cited and come away with the idea that each and every body functions exactly the same, so there’s no reason anyone should be fat – ‘it’s calories in/calories out, just get up off your fat asses and move already and put down the food you fat fuckers and you’ll be thin and acceptable like we are’. That’s why the outrage – people don’t have any critical reading/thinking skills anymore and refuse to see past the stereotypes when the information is put out there for them in black and white. They don’t want their version of the world disrupted, they would rather keep on stereotyping, stigmatizing, shaming, and blaming fat people than think that they’ve been bigoted chucklefucks their whole lives.

    • July 30, 2012 11:34 am

      I see what you’re saying, but I also see what Bronwen is saying. But first, what is “overeating”? If each body has a unique metabolic rate, as well as caloric requirement for that metabolic rate, then a person with a slow metabolism has a different caloric “requirement” than someone with a fast metabolism. Establishing the actual metabolic rate of a person (as opposed to using equations to estimate that metabolic rate) is expensive and difficult, so it’s not likely that most people will be able to establish a baseline “eating” level to which overeating can be compared. Also, weight gain itself can be a symptom of something other than overeating, and overeating can be the result of the body going into energy storage mode. People tend to eat more during times of chronic stress, as the body is storing energy to deal with whatever the crisis at hand is. This may lead to weight gain (as we know chronic stress does), but it isn’t the overeating itself that is causing the weight gain, it is the release of cortisol, which triggers hunger and the craving for calories. So, the relationship between overeating and weight gain is muddy, to say the least.

      But the thing is, most people have a remarkable stability of weight, regardless of fluctuations in caloric intake. So, let’s say that I typically eat 2,500 calories, but completely splurge for a week and have 3,000 calories. That additional 3,500 calories in one week will not necessarily result in an extra pound of weight (as the equation 3,500 calories per pound states), nor will one day’s 500 calorie excess lead to 1/5th of a pound after one day.

      So, I feel like there are two issues which you raise: one is that chronic overeating leads to weight gain, and while I would tend to agree with the general premise that it does more often than not work that way, I would argue that weight stability, even with a sustained caloric increase, is a more likely outcome in cases that aren’t influenced by some unmentioned variable, such as stress or hormone changes or medical issues. The other issue is the day-to-day influence of caloric fluctuation. Bronwen’s friend seems to believe (and got confirmation from an incomplete reading of the article) that if she ate an additional 1,750 calories in one day, she would automatically gain a half pound. That simply isn’t the case, and that weight changes aren’t nearly as neat as the mathematical equations we’ve been led to believe are the “laws of physics.”

      Over the course of a year, our caloric intake can vary widely, yet most people remain weight stable throughout that year because of the homeostatic mechanisms in place. Dr. Jeffrey Friedman gives an excellent overview of this phenomenon in this video:

      I don’t think it’s outrage so much as frustration that an extremely complicated biological process gets diluted into a simple equation that people attempt to use in an effort to “control” their bodies. Bronwen seems to be commenting on the tendency toward confirmation bias which prevents our culture from acknowledging the complexity of the issues, and I completely agree with her.


      • bronwenofhindscroft permalink
        July 30, 2012 11:48 am

        Shannon has the right of it. I am not outraged, as this is the way the world is.

        I was commenting on the fact that, in the end, the article says that we don’t know how long* from the moment one “eats” it takes to become “fat” on the body. From the way the article is written (keeping that bit of “we don’t know” to the very end), the average person sees “12 hours” at the beginning, and thinks it takes 12 hours to get fat.

        Never mind that it truly is a much more complex and complicated issue, and that the real answer, that it is such a complex and complicated issue nobody can tell, is stated in the article at the end, if they would just read that far.

        *Notice also that the question wasn’t “IF I gain weight.” The question in itself contributes to the “it’s all your fault” mentality. “How long after I eat is weight added to my body?” is engaging in the faulty premise that calories in = calories out, and if one over eats, one will always gain weight. Which is, of course, not the case.

  3. July 30, 2012 5:17 pm

    The role that confirmation bias has played in the oppression I have been the subject of from almost every area of my life ( social, career, from medical providers ) when it comes to weight related issues like this one is outrageous. I think we ratchet ourselves down to simple annoyance as a survival tactic because the massive injustice that I live with simply because of the size of my body is so omnipresent and oppressive and is often (perhaps mostly) based on misreading of the science as illustrated in this post.

    Now imagine that you were the victim of this kind of injustice five or six times an hour for your entire life and when you push back there are more and more waves of attack for simply challenging the erroneous conclusions with facts.

    I for one am beaten. I have maybe 1/1000 of an ounce of fight left in me. The good fight that folks like the bloggers of FFF encourage me but I have been beaten down so far that I just have disengaged from almost all public life because I just can’t deal with the oppression and hatred and the obstinate refusal of the perpetrators to consider the facts that invalidate the basis of their hatred and bias.

    I will always just be a weak willed disgusting, lazy, slothful waste of humanity to most of the world. Try living your entire life with those messages coming at you five of six times and hour from every part of the society you are just trying to live your life in.

    Sorry to rant and whine, I am just so tired of all the bullshit.

    BTW… two separate wight loss/ lose weight at our gym commercials on the TV playing in the background while tying this.

    • July 31, 2012 10:41 am

      Ivan….though I’m sure others have experienced what you have (the daily oppression/disapproval/attacks) but you are the first one to actually state it, at least so far as I have seen. I feel your pain and I’m also tired of it. I’m also tired of being made to feel that I need to keep quiet about it, even within my own family. It’s like people just don’t get it and don’t want to. Our society has so eradicated empathy and understanding that we are constantly bombarded with “well meaning” bullies! That’s exactly how I see it. And it’s not just about weight. I’m going through something personal due to a death in my family and the fact that it has left me without income. I have one friend who truly empathizes, doesn’t judge me for my mood swings and never ever makes me feel that I’m not allowed to feel what I”m feeling. I try not to take out my frustration and anger on others, but I’m human and sometimes their comments and encouragement is misplaced and thus I am left apologize to those who just don’t get it, either due to the fact that they don’t know everything and don’t bother to ask why I might post “The universe hates me”….they just say…”Love the universe and it will love you”….seriously? Sorry, but when you pray and hope and send out good vibes and wait for them to come back to you and you get nothing…then you start to doubt there is anything to have faith in. But I digress. I’m empathize with your plight and I agree that this happens every day. I also feel your lack of fight…I too am starting to fail in that regard. I think the “global” community is a failure and we are more selfish, self centered and self involved than in any other era.

  4. July 30, 2012 7:45 pm

    The first thing I thought is that I’ll never pay much mind to anything that talks to David Katz. That fatphobic, patronizing, concern-trolling fuckhead can kiss my fat ass.

  5. July 31, 2012 7:24 am


    I was actually interested in a different physical (reverse?) situation too, which isn’t really addressed. I wonder if there is another study out there that talks about how long it takes to “see results” after someone has exercised. I think that would be equally or more difficult to determine since there are so many variables with exercise–gaining/losing water is a big one, changes in muscle mass vs. fat, metabolism working harder AFTER you’ve exercised–stuff like that. Not to mention, to actually “see” results I suppose you’d have to exercise out many thousands of calories, which just isn’t practical. Oh well!

    Not that I really care about that sort of thing, it was just another question that popped into my head after reading the topic in this post. It has never occurred to me to ever wonder about something like this before.

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