Calories and weight

So 3600 calories = 1 lbs of fat.
I eat 1 lbs of ideal cooked meat (no fat/carbs/minerals/etc. Assume it came from a spherical cow). After it is cooked it is 40% protein/60% water. According to my calculations that is 3600 x 2/5 x 4/9 or 640 calories which translates as less than 0.18 lbs gained.

If I weigh myself after eating I weigh 1 pound heavier due to the food in my gut. How much will I weigh after the food is digested. Assuming it is less than 1 pound, how did I lose the weight through digestion?

First of all, remember that you need to eat calories in excess of your energy usage to gain weight. If your basal metabolic rate is 1800 calories, and you sit around all day playing Flappy Bird, then you would gain (roughly) one pound by eating 1800 + 3500 = 5300 calories in a day.

So that leaves the question of what happens if you eat exactly 1800 calories, neither gaining or losing weight over the long term. The primary byproducts of your metabolism are water and carbon dioxide, excreted via your urination and respiration, respectively. That means that losing weight contributes to global warming. So, really, we fatties are doing the world a favor.

But also note that if you play flabby bird, then you will save a few pounds as your brain shrinks and your IQ drops :smiley:

Due to the process hinted at above, your weight in the short term is not directly beholden to the 3500 calories = 1 lb rule.

To see this in a very simple example, consider water. If you drink 16oz of water, you will in the short term gain 1 lb. Water has no calories so how is this possible? Simply because the weight of the water is added to you (the same as holding the water in a bottle), but as soon as you eliminate this water, you will of course weigh less.

The 3500 calories comes into your how your body processes food intake. As mentioned in the first reply, it is if you consume 3500 calories more than you require to survive, you will gain a lb or if you use 3500 more than you take in you will lose a lb. That is just a general number to help you see how much you have to cut to lose 1 lb of weight.

In reality, depending on the diet plan used, you could lose a lot of excess water. Or you could lose muscle, or you could lose fat, or you will likely lose some of all of them.

In the longer term, it mostly balances out. But still your intake vs your output can vary greatly.

The aforementioned steak will likely take a while to digest and will be eliminated over a period of time accordingly.

That’s not the right equation.

I pound equals 454 grams. If 40% of it is protein then 181.6 grams of it are protein. (272.4 grams are water.) Each gram of protein provides 4 calories of energy. So 454*.4*4 = 726.4 calories.

Calories are a unit of energy, not weight. To burn 1 pound of human fat tissue it takes approximately 3600 calories. The reasoning is given here.

You put a set amount of weight into your mouth. Some portion of it is used as energy to power your body, a second portion of it is excreted through perspiration, respiration, and digestion, a third portion of it is converted into body mass. The three portions must equal the weight entered. Note that the third portion can be zero, but this can only be the net result over time.

Very apposite.

OK this isn’t a weight loss/diet question.

Assuming my diet exactly matched weight loss due to metabolism so that every day I neither gain or lose any weight …

If I eat a pound of steak in addition to my perfect diet over the long term (24 hours to complete digestion) will I add 0.18 lbs? 1 lbs? somewhere in the middle? If less than 1 pound, how is that accounted for since I ate 1 lb of meat?

You did not eat 1 pound of meat nor did you eat 0.18 pound. You ate 6.4 ounces of protein and 9.6 ounces of water (i.e 40% protein and 60% water).

There is absolutely no way to predict in advance whether you gain weight or how much weight you would gain if you did. We don’t know your original state nor your metabolism. We don’t know your weight, your nutritional stance, or your fat levels. We don’t know if you are eating anything else. We don’t know how active you are being. Converting food is a unique process, with every meal you eat during your life contributing to your unique needs over the next day.

Is there anything at all to say on this? All we know for sure is that you ingested 726.4 calories. Other than that, you can talk about averages, which say very little. The average adult burns 1200 calories in a day doing nothing at all. Normal activity can double that. Heavy work can triple or quadruple that. So if you are taking in only 726.4 calories of energy, you will actually lose some weight because your body will have to burn some of its stored flesh (fat first, then muscle) just to stay alive. (I’m assuming that the water will go through you and be balanced by output.) This has nothing to do with the weight of the food you took in. If you added a pound of water, you would lose more than if you took in a pound of fat. The only thing that matters is the difference between the calorie content of your intake and the calorie expenditure of your output.

1 pound of steak (New York strip) is 128 grams of protein, and 32 grams of fat. The rest is water mostly.

That’s 512 calories of protein and 288 calories of fat. About.

Roughly 25ish percent of protein calories is used to digest and metabolize it (thethermic effect of food) and roughly 10% of fat calories. (With a decent range but roughly.) So that’s a net 384 from the protein and 259 from the fat, total of 684 excess calories.

1 pound of fat tissue is equal to roughly 3500 (or 3600 deoending on what source) calories and 1 pound of muscle is equal to 600 calories. If you gained all fat then you would gain about 0.19 pound; all muscle about 0.64 pound. Odds are it would be more fat but not all unless you were also doing a fair amount of resistance training. So likely about 0.25 to 0.4 pounds as a WAG.

For sure less than a pound. Breaking it into pieces and rebuilding it … well to use an apt turn of phrase, there is no free lunch. That takes energy and more for protein than most other food sources. And the storage is like to be in a more compact form.

Yet again :smack:
Assume all the other food I eat that day perfectly balances with the calories I burn so not counting the meat it is a net zero weight gain/loss.

How much weight will that pound of meat add after digestion?

Of course assuming that the intake does not impact the perfect balance you are otherwise in. Maybe the big steak makes you sleepy so you move less, or the higher protein gets you moving more … in either case the calculations change.

Yet again. :smack:

If you take in 6.4 ounces of perfectly digestible solid food, and all your other metabolic needs are perfectly balanced, you will weigh 6.4 ounces more after eating. (Assuming, once again, that you are not retaining water for some reason.) This has nothing to do with calories; all that matters is weight.

Food is either used by the body and excreted in various forms or not used by the body and retained in various forms. (For the nitpickers, a tiny amount of calcium or iron or other elements may be needed for long term use, but since we’re supposed to assume balance then we can assume they are merely replacements for normal loss.) Your assumption is that all the solid food intake is not used by the body and not excreted either. Therefore, it must all stay within the body. All the numbers and sources and forms can be discarded; your question is simply about inputting weight. You could add it in the form of lead sinkers and come up with the same answer.

Just not correct and here is a law of thermodynamics. No perfect machines.