I have friends who have started diets using the 3500 calories = 1 pound formula.
They’re always surprised during the first 1-3 weeks of the diet to lose much more than 1 pound per calculated calories. This is because their new diet is not only regulating the number of calories they intake but, as a consequence, also tends to be more healthy - less fat content, less sugar, and (more importantly to the immediate weight loss) less salt.
When someone who has been eating a fairly fatty and salty diet suddenly switches to a normal intake, their water retention generally drops very quickly. At my work, I’ve had a lot of people talk to me as they go on diets (I’ve been on the Safety Committee for a few years), and many can lose 3 or 5 or more pounds in their first week. They then say, “Wow, losing weight is easy!” I tell them not to let those numbers fool them, and in a few weeks, it’s challenging to keep up the 1-2 pounds per week numbers.
The graphs on p. 1525 show near 100% absorption by the end of the intestines.
This is one of those things that everybody knows but is surprisingly difficult to pin down, probably because it’s taken for granted.
Here’s an old thread with a nice long post from gabriela on the workings of the colon. There is also a reference to feces composition, but it comes from a student’s course notes, and I think it’s somewhat oversimplied.
No one except you is talking about the number of calories found in feces. What I am talking about is the impossibility of your claim, right up there, that eating a pound of fat would result in a weight gain of 1-1/7 pounds. There is such a thing as the conservation of mass. While excercising your google skills you might want to look up the thermal effect.
Well, actually, jormundgondir asked exactly that, which is why I answered it. And that answer also shows that digestion extracts virtually every calorie, which had also been questioned.
As I said before you’re confusing two different effects.
Food does not turn directly into weight. Fats, carbohydrates, and proteins are broken down by the body into their basic components, fatty acids, glucose, and amino acids. Those building blocks are then taken, mixed together, recombined, or oxidized. This involves additional chemicals outside of those included in the ingested food. Therefore food is not a closed system and you can’t apply the law of thermodynamics to weight gain.
In addition, calories are not a measure of weight but a measure of energy. It’s true that those are loosely equivalent, but loosely is the operative word. (It’s also true that fats do not equal 9.0000000000 calories per gram. It’s an approximation.) That’s why I said earlier not to let the pounds to calories ratio fool you. When you take in 4086 calories from any source, you body can use that energy to produce that much energy or convert the substances the calories come from to about 1 1/7 pounds of tissue. It doesn’t matter what the calories come from. The important thing to remember is that the starting weight and the ending weight are from two different sources.
That’s also why it’s so hard for people to eat 500 fewer calories a day and lose a pound a week. The conversion involves practically everything your body does. Michael Phelps can eat 12,000 calories a day and not gain weight because he burns off so much of it as energy. Even a totally sedentary person burns energy as long as life lasts. When your food intake changes, your body’s metabolism changes to accommodate that.
The simple reduction over the long term, though, is exactly what I said originally. If you eat an additional 3500 calories over what you are burning off you will gain about a pound. Therefore if you eat more than an additional 3500 calories over what you are burning off you will gain more than a pound. That is in fact simple chemistry and simple physics.
That is untrue. If you eat a pound of fat, which you claimed has 4086 calories, will not gain more than a pound. You can not gain more than a pound. What you said is that I can stand on a scale and weigh X pounds, then stand on the same scale with a pound of butter in my hand and weigh X+1 pounds, then eat the butter and weigh X+1-1/7 pounds. Mass has to be conserved, it doesn’t appear out of the lumineferous ether.
No, it appears out of air. Specifically, most body tissues contain a blend of significantly oxidized substances, while fat is not significantly oxidized (that’s why fat has such a high energy density – compared to carbohydrates and protein, it’s almost all carbon).The extra weight is mostly oxygen.
As I said earlier and Nametag confirmed, the extra weight comes from a different source.
Maybe it would help to think of it this way. In the real world, separate from thought experiments, food is a mixture of carbohydrates, fats, and proteins. Carbohydrates and proteins are only 4 calories per gram, so your body requires two pounds of them to extract 3600 calories. If you take in 5 pounds of food - 2 carbs, 2 proteins, 1 fat - over what you burn off you’ll end up with 3 1/7 pounds of weight.
Mass is always conserved, but the system we’re considering is the food taken in plus the entire body’s stores plus the energy made available by respiration. You can’t abstract a piece of the whole system. That’s guaranteed to give the wrong answers that are confusing you.
Thanks, I had come across references to the semi-starvation study before, but never anything concrete.
So it does seem like BMR does actually slow down when you limit calories, most significantly in non-obese persons.
My interest in the topic comes from personal experience with limiting my caloric intake, I have personally continued losing weight as long as I have been at a deficit, even now when I’m not obese anymore.
It appears out of air? Even though the respiration process converts one mole of inhaled oxygen with an atomic mass of 31.9988 to one mole of exhaled carbon dioxide with an atomic mass of 40.0088? Well, you learn new things every day.
You’ve probably already realized, but when these people go on diets, they’re probably going from around 500 calories over their basic needs (basic metabolic rate plus energy ‘spent’ on movement and the like) to 500 under their BMR.
I found this was likely to be the case for me anyway, as I lost 7 pounds in the first 3 weeks of my diet. I used to eat far more than the 2000-2200 calories I need, probably around at least 3500 calories a day, as I was eating massive portion sizes, and was (albeit slowly) putting weight on.
This might have already been said, but I’ve been away from the thread and I’ve only read as far as your post so far
Perhaps I’m just being a bit dense, but I’m still a little confused - if you eat an amount of food worth 3500 calories, and that amount of food weighs less than a pound, would you still gain a pound of weight?
Thank you for this cite. 50 years ago it was probably a little easier to line up a dozen “volunteers” (medical students and workers, no doubt) who were willing to have anal and oral tubes passed for the sake of science.
It should be noted that a 500 cc liquid meal containing pure sugar, powdered milk and pure corn oil, delivered as a single event into healthy volunteers in a fasting state is not even a first approximation of a normal diet or the ordinary efficiency of caloric extraction, so I do not agree that one can extrapolate from this study that most people extract nearly all of the energy out of most of what they eat–particularly if they are over-eating. It would appear that this study was done more with a design to find out what gets absorbed where, and not as an effort to find out how efficiently a typical diet is converted into energy available for metabolism and storage.
I nevertheless appreciate the link and enjoyed learning from it. Thank you.
If you consume nothing but fat, you will die in a matter of days. If you consume nothing but fat and water, you will gain weight from both, even though the water has no calories. If you’re eating such that you’re maintaining a constant weight, and eat an extra pound of fat (keeping exercise etc. constant), you’ll also either consume more water, or pass less, and gain more than a pound of weight.
Quite so. Lab rats of the human variety and real world variation can be deceiving.
I’m not sure why you think “over-eating” would be a problem, though. Perhaps food competition over-eating would overload the intestines but I know of no reason why even large quantities of an ordinary diet would result in any less nutrients being digested. Just the contrary. If extraction wasn’t just as efficient for over-eaters we wouldn’t have the obesity problem. The extra calories would be excreted. Problem solved. In the real world, larger portions or more calories-dense foods result in slower transit through the intestines, giving them more time to extract all the possible calories and those go into storage in the body as fat.
Appreciated back. I didn’t mean to get testy with you earlier, but there is so much ignorance about the way the digestive system functions that I wanted to keep the arguments as focused as possible.