Adipose tissue is almost wholly fat and water at 70% and 22%, respectively. These tissues' cells are only about 8% protein, and they make up an average 12% of the human body. Gaining a pound of this tissue requires roughly 3500 calories in excess of a 2200 median diet. Muscle tissue is mostly protein, around 22%, and the expected constant of 70% water, with a low 8% fat, and is about 38% of the human body. Calorie-devoid water is 70% of a human body's tissues overall. Blood and bone are volume-food, being mostly indigestible on the side of bone and mostly water for blood. That said, blood (due to a high sugar content and about a 7% protein volume) possesses about 450 calories per 500 mL, and the average human body contains about 5.5 liters of blood altogether. There's also glycogen, a compound stored in relatively small amounts (about 500 grams per human). That's your carbohydrates, and they don't tend to vary much with a person's weight.
Digestion takes approximately 1.5 hours under stable conditions within the human stomach, and up to 45.5 more hours to traverse the rest of the digestive system. The human stomach has a rough median capacity of about 0.94 liters, which facilitates the time of 1.5 hours for the stomach to churn its contents into chyme. The average human body, however, has a total volume of approximately 66.4 liters. Through linear extrapolation, we can assume that digestion of a human body within a distended human stomach might take roughly 4.4 days (106 hours). From there, we spend the next 4.5 hours in the 3 liter small intestine, a time of 4.1 days for a full human being (99 hours). The large intestine, or colon, usually tends to take the longest time out of all the "stops" in the digestive system, going up to 40 hours on average. Its volume is roughly 4.5 liters, and so its processing of a full human being would take about 24.5 days (590 hours).
You may note that the times here are a bit different, proportionally, than the normal human digestion of food. This isn't a miscalculation, it's a result of the food's volume versus the digestive system's components' volumes affecting time.
The average weight of humans the world over is roughly 136.7 lbs (62 kg), so we'll use this as our base androgynous meal for calculations.
50% of the human (81.9 lbs) is totally-digestible meaty tissue, 35% is skeletal tissues (20% of which is digestible trabecular bone and marrow, a fatty set of tissues), 4% brain (which is, in turn, 60% fat), and 11% blood solids, lymph, or other watery gush.
So!
Digesting a human being will take 33.1 days (795 hours), yield 139,725 calories (109,661 fat cal.; 23,461 protein; 2,000 carbs; 4,603 blood sugars), produce 40.5 lbs (18.4 kg) solid waste, and cause you to gain about 19.1 lbs (8.7 kg), assuming a semi-active lifestyle of doing anything more than just lazing around in front of a computer all day. A sedentary lifestyle will result in a gain of about 24.3 lbs (11 kg), You won't actually produce direct liquid waste from this alone, at least not in excess of the norm, and will still need water intake––the human body only holds a 24-day supply of water! Moreover, most of your supplemental hydration would be during the first 4.4 days––the colon and small intestine absorb far, far larger volumes of water than the stomach.
Also, it might be prudent to add this: as prey, you may want to regulate your breathing. If you remain calm, you're likely to go unconscious from asphyxiation in around 8.6 minutes. In a panic, however, you have 48 seconds. You die 15 minutes after passing out either way, so hey, maybe it doesn't matter at all.
Question Corner:
DethXev wrote:Ok, now I'm actually curious and too lazy to look it up...I can understand why bone is indigestible but brain, blood, and lymph is also unnutritious and/or indigestible as well? Why is that? If so, then what is the purpose of eating this "junk food" from animals (for those people who actually eat these parts I mean)?
It IS nutritious, but doesn't provide any statistically significant calories. You can get vitamins, minerals, etc. from it, but you won't get energy, and I did not calculate this to provide full human "Nutrition Facts."
[EDIT] To add to this, I want to point out that, yes, bone material is digestible and, no, it does not have a significantly high caloric content. It is almost totally indigestible when whole, and would not fully digest unless ground up. Bone marrow, however, is a significant source of calories that I had overlooked, and I will factor changes accordingly.
AndrewLondon wrote:I'm interested in how you allowed for the fact that as food gets larger then volume scales as the cube, but contact surface scales as the square. (Your paragraph four?) Not because I want to check your work, but because it's hot to think about the stomach being stretched glassy-smooth as it struggles to process the sheer scale of the meal.
Great post, enjoyed it a lot ^^
The reason I scaled solely for volume is that there's no real evidence to support that surface area contact regulates the speed of the process. While it is the most important fact of digestion, it does seem that the mass of a meal has a greater impact on its speed through the digestive tract than the extraction of nutrients from it. I realize that volume and mass are not equivocal, but I can only believe in this lack of actual experimental evidence that the volume matters most in the passage of the food.
That said, I also have to believe that the amount of time the food is kept inside the digestive tract in this thought experiment (the 33.1 days) would be enough for it to be properly sifted through and leached of nutritive value by the system. I'm not going to pretend it's an infallible assumption, but it does seem logical enough.
I'm glad you enjoyed reading, too~ <3
