In a universe where humans can take elective surgery to render themselves ruminents, what would be the effect of that surgery in regards to weight?

To keep things simple:

  1. The surgery involves the addition of the four stomachs
  2. The weight gain does not include the weight of the additional stomachs as a result of the surgery, but rather natural post-surgical gain

What would happen if

  • A) The human subject kept to his previous diet (i.e, burgers and soda), merely adjusting the amounts he'd need in order to sate his hunger

  • B) The human switched to a ruminant diet (i.e., grass)

In each of those situations, would the human gain or lose weight had he not had the surgery?

  • 1
    $\begingroup$ 1. the persons teeth would rot away in no time, stomach acid is hard on human teeth 2. you have to double the size of his torso to have room for all the additional organ space. $\endgroup$ – John Jun 21 '18 at 20:24
  • $\begingroup$ Do recall that ruminants stomachs are for breaking down cellulose in plant fibre, which is rather lacking in burgers and soda $\endgroup$ – nzaman Jun 22 '18 at 6:39

Note: I'm not a biologist

The key problem with this is predicting what the human's hunger would be like after the surgery. We can't talk to cows or other ruminents, [citation needed] so we can't predict what effect multiple stomachs would have on human hunger. On top of that, since this surgery doesn't exist in the real world, I have to wonder if the other 3 stomachs are artificial or transplanted. Is the human even capable of feeling them, or is his appetite entirely based on his natural stomach? Basically, you're going to have to make up the impact on his hunger. Once that's done, you'll want to figure out the potential for fermentation of the food he's eating and what that fermentation will do to the calorie density of the food. It seems that human hunger is mostly governed by the volume of what we eat, rather than the calorie intake. [citation: I have a human stomach] The ruminent process may change the caloric value of his diet, causing him to gain or lose weight. That depends on his diet and his hunger, and even if I had complete details on both, I'm not familiar enough with biology to know how to calculate it, so I'll have to leave the calculations to you.

Another problem with your second question on switching diets is how many calories a human needs vs how many he gets if he replaces his diet with ruminent-digested grass.

None of this takes into question taste. Unless there's some tongue-surgery going on, too, it's going to be tough to make a ruminent diet palatable - whether that's grass or just partially digested food all mixed together.

One more over-all concern: I would argue that any weight loss he experienced would be a sign that he is getting full without getting enough calories, and he will need to force himself to overeat the same way that most dieters force themselves to under-eat. Granted, most of us would prefer that outcome, but given the taste issue and the drastic surgery, this sounds more to me like a human centipede situation than a weight-loss solution.


My opinion is that it could not work at all.

first of all, surgery would also need a radical redesign of the mouth. Mastication here becomes vital to break down the grass' fibers, that's why cows seem so slow in their eating. If we tried to do that with out own teeth, they'd get corroded, cracked and finally would break.

Second, the real problem here is that we are not made to be ruminants. Even changing the digestive apparatus, our body wouldn't be getting any more proteins and nutrients we need to stay healthy. We'd die of nutritional deprivations.

But, on a comic side, since the four stomach serve to keep breaking down that tough grass (remember, it must come back as cud to be remasticated, yuck!) during digestion we'd have to expel all that fermentation gas. Elevetaros will need complimentary gas masks or a strong ventilation! And zippos would be forbidden in restaurants!

  • $\begingroup$ "We'd die of nutritional deprivations." So you'd get skinnier. That answers my question. +1 $\endgroup$ – TheAsh says Reinstate Monica Jun 24 '18 at 10:08

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