How efficient is the human digestive system? What affects how many calories one absorbs?
Assuming you are a man and normal in that you aren’t incredibly active, you aren’t going to absorb much more than about 400-450 calories at any one sitting. Most of the rest of this is going to get stored as fat, unless you are pretty active. Your best bet is to eat about 5 meals a day at about 400 per meal if you aren’t active, and you need to make adjustments for more calories the more active you are.
If you are living an ‘active’ lifestyle, then you should of course eat more per sitting.
Your body is a marvel of many complex machines, and very efficient at a lot of things.
How can you store calories as fat, unless they are first absorbed?
So you’re saying that if you eat one 800 calorie meal a day, you will get fat? :dubious:
Does the body always store excess calories as fat, or does it expel some? If the later, under what circumstances?
That’s not what I am saying. Actually your body won’t absorb all 800 calories in that sitting, but throughout the rest of the day the rest of what you ate will be used up. (hell a man my height–6 foot four and weight burns about 900 calories sleeping for eight hours!)
I’m telling you that if you eat one large meal a day (say all 2000 calories) you aren’t going to lose weight, like you would if you broke it up into 5 separate meals. Your metabolism isn’t going to benefit from one large meal a day. In fact, you’d gain weight, unless you were fairly active.
My post assumes a fairly sedentary lifestyle.
I think you’re missing the question. The question isn’t about how the calories are stored, it’s about how efficient the human body is at extracting the calories in the first place.
To be more gross about it, how many calories are in human waste? That’s the real question. If I eat 1000 calories, how many stay in my body, and how many pass through?
I very well may have. And I would like to know how much of it (if any) ends up as waste.
It depends on various factors.
For example, consumption of calcium will actually reduce the number of fat calories absorbed by the body. It will actually pass in your waste and can be measured. It takes a fair amount of calcium to cause a decent amount of fat to pass unabsorbed, but it is very ‘do-able’.
However, all that aside, the human body is incredibly efficient at absorbing calories. Very little is wasted. In various studies not at my fingertips, one thing is consistent: Dang, it’s really hard to get the body to pass food/waste without it extracting all the calories.
In the short term, it might matter how you ingest your calories, but it doesn’t matter how you span the calories out over the long term. If you eat five 300 calories meals or two 750 calorie meals or one 1500 meal a day, over time the two approaches result in the same weight loss.
Taken to extremes, you could gorge on 5000 calories and see many go unabsorbed if you have created a situation so upsetting to your digestive system that you get sick and your body works to push things along. You might experience runny stools and vomitting, which are – of course – obvious signs that your body has chosen to skip the absorption and make room.
How much is a fair amount? Does it matter what type of calcium it is?
Does anyone know the answer to this question? Ok, ok, the body is effecient, and almost all calories are taken, etc, etc, but, how many calories on average ARE in poop?
Typically about 4-5 servings of non-fat dairy.
You might shed an extra 2 pounds every 45 days above/versus a diet that did not include non-fat dairy. Of course the dairy servings are going to have calories, so they must come out of the 2000 calorie balance you eat daily. Therefore, replace some foods with non-fat dairy options, such as cheese made from skim milk, non-fat yogurt and other things I can’t think of right now. Do that about 4-5 times a day and the calcium with actually prevent some fat from being absorbed.
I wonder why some moon-bat hasn’t come up with a diet based on this? “Eat chalk and watch the fat melt away…”
Depends on the food. To get even more gross than Sam Stone, ever notice some identifiable bits in your poop? You didn’t get any of those calories. 
But a soft drink probably gets mostly absorbed since it’s basically sugar water.
I hate to reference Oprah here, but Dr OZ did cover a study that had good controls and had two women literally digging through and analyzing the stool samples of a number of people over a period of time.
Here’s a link:
Also, keep in mind that many supplements do do quite what they do when they actually come from the food you eat. So, taking calcium supplements might not do the trick. You might have to actually eat the calcium in it’s original state. I know there are different calcium supplements and different data on just how effective they are.
Isn’t a calorie just the amount of energy released when stuff is burned? Poop is extremely burnable, so I assume there’s a bit of caloric value to it.
Well, by E=mc[sup]2[/sup] a 100g turd would have 2,151,051,624,000 calories according to my calculations.
Depends on the poop, no? Poop from a cow is more burnable than poop from a wolf-- right? That would be because the cow’s poop has a lot of plant fiber in it.
Burning turds does not convert matter into energy.