Re: Semi-realistic Regeneration and corresponding Increased Consumption
 

Well, I am, a bit, but that's something of a . . . necessary analogy, because the original TL10 Regular Regeneration biomod comes from nano. I'm actually trying to get something more plausible-sounding and less cliché. A borderline organic construct that is halfway between blood cells and nanites is approximately what I'm hoping for. Things are meant to be weird-sciencey, with mild TL^, but not something as drastic as ignoring conservation of energy. It's meant to be based on rare and weird divergent strain of humanoids of the setting (who tend to have both detrimental and beneficial mutations). Great Old Entities are involved by proxy, but the overall style of the setting/campaign is meant to be soft sci-fi//science-fantasy, not pure fantasy/horror. I'm not sure how many of these details are relevant/interesting/useful for this discussion.

Stuff that says that recipients really should get Resistant to Metabolic Hazards too if they want to use it is actually appropriate for this invention.

Re: Semi-realistic Regeneration and corresponding Increased Consumption
 

Most likely the biggest reason why most animals store most energy as fat is more due to how it's possible to store it in pure form. Sugars are so water hungry that you end up storing far fewer calories per gram than fat when you include the dead weight.
I imagine concentrated ethanol has its own problems.
Then again, making your very tissues toxic to most other organisms even if it costs you something in return isn't inherently a bad design.

Re: Semi-realistic Regeneration and corresponding Increased Consumption
 

Using loads of protein for calories blows out organs from all the excess nitrogenous waste.
There really are good reasons why carbs are the go to foods for most omnivores. We diabetics not included. ;)
But even I feel the pinch as it seems to take more effort to bring my reserves to bear than it did before the -betus. Possibly unrelated and anecdotal of course.
For hummingbird level metabolic activity that super regen. would require though, boat tons of sugar seem about the most plausible fuel.

Re: Semi-realistic Regeneration and corresponding Increased Consumption
 

Ethanol doesn't seem particularly energy-dense. The idea of recharging by consumption of large amounts of ethanol is amusing, though. And yeah, tissues being toxic (by our standards, that is) is quite par for the course for many lifeforms of the afflicted area. But many of those solutions would not be suitable for biomods installed into more human-like humanoids, since they would require replacing all cells with more robust ones. Now, dumping toxings into blood as byproducts and having them immediately handled by the boosted filtration systems - that's about perfect from the conceptual PoV.

Re: Semi-realistic Regeneration and corresponding Increased Consumption
 

A pound of fat optimally has around 3600 Calories. How much energy is your character needing that that density of storage won't keep him going between meals?
I think men can go down to around 5% body fat safely, and no one's calling one with 15% unhealthy. That gives a full 10% to play with. For Gurps 150 lb, that's a full 15 times 3600 or 54000 Calories storage. Multiplied by 4.184 means over a quarter of a million kilojoules.
Assuming I did my basic math correctly.

Re: Semi-realistic Regeneration and corresponding Increased Consumption
 

Well, only our stomachs can handle such a low pH, so it might be possible to create a very insulated organ for ethanol storage. But risky as heck, I agree.

If you want something that's going to cause major total body effects, it seems difficult to implausible not to have to screw around with all tissues in some ways.

Re: Semi-realistic Regeneration and corresponding Increased Consumption
 

How much energy (and materials) is needed is a hard question, which some people above attempted to answer. Anthony's approximate calculations seem to yield a requirement of extra 15 meals per nychthemeron of regeneration (about 24-25 HP).

Carrying 15 meals worth of energy and nutrients seems like it'll be no less than (¼ lbs × 15) = 3¾ lbs per day of supply. Which seems . . . very noticeably more than the typical day-to-day mass change (most of which is water anyway), but about plausible for a boosted organism.

There is however one interesting side effect of such an ability:
if the organism can store and 'pull out' this much stuff from storage on a short notice for regeneration, it stands to reason that it can also be used by the organism to mitigate FP loss from starvation equivalent to those same 15 meals. Which is actually a lot, essentially comparable to 5 days of Doesn't Eat that can be 'recharged'.

Re: Semi-realistic Regeneration and corresponding Increased Consumption
 

Ethanol is only 26MJ/kg, compared to fat's 37. So it's no good for storage, only for quick delivery. As I said, getting some extra energy by rapidly consuming ethanol, and having the the boosted inhuman-garbage-collector blood cells quickly clean up all the byproducts (and sending them on their way out) would be an amusing detail, but that's probably about it.

Also, there's a difference between stuff that permeates all tissues and stuff that only accumulates in large amounts in specialized cells. E.g. the concentration of oxygen in erythrocytes would probably be unhealthy for some other tissues, even while smaller concentrations of it are quite necessary for all or nearly all cells.

Re: Semi-realistic Regeneration and corresponding Increased Consumption
 

Some fruitbats can more-or-less properly digest alcohol (I understand it's not so much that they don't produce the toxic byproducts, and more that they tolerate the toxic byproducts). They aren't inedible either, at least as far as I know.

I assume many fruit-colonizing insects can tolerate at least some of their diet being alcohol too, at least for the phase of their lifecycle where they live in the fruit. Otherwise they'd be pretty screwed.

Your regeneration doesn't necessarily need to be powered by booze, if the organism simply uses alcohol as one nutrition source of many to build back up and/or maintain its fat reserves for the next bout of regeneration.

Fat is more calorie dense than sugars or alcohols, but digesting lots of fat takes specialized anatomy. Polar bears take a huge portion of their diet in fat, and may be the world leader in terrifying bile production. Polar bears will even kill seals just to eat their fat, leaving everything else, because of the huge amount of fat intake they require. Polar bears, of course, are using all that fat to not freeze to death; females even bigger reserves when pregnant and nursing, because they den up and don't eat during that period.

So as a side effect, they have freaky bile sacks producing really potent bile. Bile, of course, is a detergent that breaks up the fat and makes it water soluble, making it biologically available. If you don't have enough bile for the fat you're eating, the leftover fat will just go out of your body (which is nasty). So there's another modified organ that you don't need but will probably want to support this.

Re: Semi-realistic Regeneration and corresponding Increased Consumption
 

You can do better than fats by having something that's closer to the finished product and thus requires less energy to finish the job. If we've got some form of material that can rejoin damaged tissues more effectively than existing mammalian biochemistry (coagulin et al), your least weight option is probably to store deeper reserves of that material, and package it with just enough surplus energy to power its normal transformation.

Mechanically speaking this would be closer to limited uses than costs fatigue, though limited uses is highly inefficient on hourly regeneration.