Increased Consumption Due to High ST
 

This is just a little something I've been playing around with as part of a new DF setting I've been working on, and wanted to see if the hivemind would like to weigh in. I'm wanting to have consumption scale with ST, which as I understand it would be realistic, but am not certain exactly how it should scale - and also, how this interacts with SM.

It seems like the ST bit should scale linearly with BL, but since you're not constantly using your muscles at near-full capacity, perhaps BL/2 would be more appropriate. It doesn't seem like a larger or smaller creature should expend any more or less energy than an SM+0 one to lift a certain weight, however, so I'm thinking this would be a constant +n kcal/day per +1 BL (which, using humans as a model and assuming 3000 kcal/day - what GURPS roughly does - works out to +75 kcal/day per +1 BL). Does that seem appropriate?

For accounting for SM, I'm just using the relationship established in Biotech (consumption is the square of scale) to establish a base consumption for a given scale, then adjusting that for ST at +75 kcal/day per +1 BL. Does this sound ballpark accurate, or am I completely off?

Yes, my version of pixies (who are ST 5, when by size they should be around ST 1.5) are going to be absolutely voracious eaters. There's a reason they are known for having done extensive research into extradimensional storage bags and the like.

Re: Increased Consumption Due to High ST
 

In my current campaign, which has humanoid races with expected ST ranging from 5 to 14, I use the simplified model that daily food intake varies with Basic Lift. A ST 10 human needs 3 meals a day; a ST 7 nixie needs the equivalent of 1.5 meals; a ST 14 troll needs the equivalent of 6 meals. However, because their stomach volumes scale with weight, not BL, a nixie needs more small meals and a troll needs fewer big meals.

Re: Increased Consumption Due to High ST
 

The units of Basic Lift x Move Rate come out in energy, and it looks fairly reasonable. Food consumption should be linear in energy. Yeah OK for warm blooded things there is a size dependent term in there too, but big warm blooded things are generally going to be strong, fast or both, so probably close enough.

Re: Increased Consumption Due to High ST
 

It's mostly a problem with small warm blooded things, not big; the rate for being warm blooded scales with temperature difference * surface area / thickness of insulation, and thus at constant proportions scales with the 1/3 power of mass, which is much slower than general metabolic scaling (which at constant proportions scales with the 2/3 power of mass). In practice, large animals need extra heat dissipation so the warm-blooded factor pretty much drops to zero when active, but there's a reason the smallest known mammal is about 30mm while the smallest known vertebrate is 8mm and the smallest insect is 0.14mm.

Re: Increased Consumption Due to High ST
 

Be aware of Kleiber's Law. Mammals' base metabolic rate scales with the 3/4 power of mass.

(There is a very interesting phenomenon in newborns in which it takes quite some time after birth for their metabolic rate to rise from that expected of a part of their mother's body to that of an independent mammal their smaller size.)

Re: Increased Consumption Due to High ST
 

That’s useful, if a bit frustrating (the article notes the reason for the law is unknown).

If we presume there is a creature who has strength well out of proportion to its mass, Because Magic, but that must still fuel that strength through mundane food consumption, do you feel it would be more appropriate to use the caloric needs of a larger creature with comparable strength, or some sort of average of this and what the magically-enhanced creature’s mass tells us? Note here we are assuming a rather active Pixie (as active as a human who needs 3000 kcal/day), so that enhanced strength is going to be seeing recular use.

Re: Increased Consumption Due to High ST
 

Depends on the details of the magic and on how it's used. Real muscle will require food energy equal to (total work done) / (efficiency) + (resting energy consumption), but there's room for considerable variance in total work done, efficiency, and resting energy consumption.

Re: Increased Consumption Due to High ST
 

I would recommend using Basic Lift x Basic Move. Enhanced Move isn't relevant, as it won't be sustained for long periods. But yes, the dimensions do come out to power, or energy/time: force x (distance/time) = (force x distance)/time = energy/time = power.

Re: Increased Consumption Due to High ST
 

If it's getting the power from oxidizing food molecules, it's going to have waste heat, which has to be gotten rid of. That's going to raise its body temperature, unless you give it expanded surface area. Maybe those wings are there for more than flying.

Re: Increased Consumption Due to High ST
 

You also need to consider waste products. A 10 lb pixie that consumes as much as a 150 lb human is going to be using the toilet 15x as frequently due to having insufficient capacity for waste products within their body. If we assume that the average human spends fifteen minutes a day using the toilet, a pixie would require proportionally longer times (nearly four hours a day). They will also need to spend proportionately more time eating and drinking, so they would end up needing 36 hours every 24 hours just for toilet, meals, and sleep (meaning that something has to give).

Re: Increased Consumption Due to High ST
 

Well, it probably has increased body temperature anyway to raise reaction rates, though that is well over linear scaling.

Re: Increased Consumption Due to High ST
 

There's a lot of speculation it has to do with the way resources are delivered by scalable networks. There are apparently some analogs in pipe wear rates or electrical line losses.

Which suggests it might not hold for very small organisms that don't have such a thing, or those that are nearly two dimensional, or arranged as thin layers around thick tubes, but I don't know that anybody has proved that yet.

Re: Increased Consumption Due to High ST
 

A bit of necromancy, but I've recently been thinking about this and think I have an acceptable solution, at least for my purposes. Going off of GURPS standard of a meal being 1000-1200 kcal (thus 3000-3600 kcal/day) and assuming an average GURPS character to be a 25-year-old male who is 5'8" and 145 lb (the dead center of Average Build for ST 10), I'm getting a Resting Metabolic Rate of roughly 50% of consumption. The GURPS standard appears to be roughly based on active military (a full day's worth of MRE's provides around 3600 kcal), who from what I understand are typically at around Medium Encumbrance. The dead center of Medium Encumbrance for ST 10 is 50 lb, and an average character has Move 5 (which gets adjusted down to 3, but as we're going to be having everything adjusted equally, that doesn't matter here). This is important because the majority of the energy above RMR a character would expend is likely going to be spent simply moving around. So, 50% of energy is spent on RMR, while the remaining 50% is used on moving around 200 lb at Move 5, for a value of 1000.

For our pixie, said creature is around 0.15 scale (around 1 ft tall), which - going off of Kleiber's Law - implies an RMR of around 1/4 of a human. As weight follows the cube of scale, our average pixie would be around 0.5 lb. With ST 5, the dead center of its Medium Encumbrance* is 12.5 lb, for a total weight of 13 lb. Pixies have a Flight Move of 10**, for a value of 130. So, the pixie's RMR (which makes up half of consumption) is equal to 25% of a human's, while a pixie's activities (making up the other half) burn energy equal to 13% of a human's. This works out to a total consumption of around 19% of a human's, which I'm comfortable rounding up to 20%.

Now, I'm probably not going to require humans with ST above 10 (and Move above 5) to consume more, so pixies with high ST or Flight Move wouldn't either. If I were to do so, it wouldn't be terribly difficult to implement - keeping in mind the 25/13 split (or rounding this to a 25/15 split), a pixie with ST 15 (the maximum allowed for them) and Flight Move 15 would be shifting 113 lb (assuming the pixie still weighs around 0.5 lb), for a value of 1695; that boosts the "13" part of the split to "169.5," for 97.25% of human consumption (they'd eat pretty much exactly the same amount as a human). A comparable human, meanwhile, would be around ST 20 and Move 8, shifting around 350 lb (assuming still around 150 lb), for a value of 2800. This changes the human ratio from 100/100 to 100/280, for around 190% of normal human consumption.

*Using Medium Encumbrance may not be entirely appropriate here. While their food supplies would be expected to be proportionally heavier, and I envision my pixies using weaponry that is proportionally larger than what humans use, this doesn't seem like it would be enough to go from hauling around 1/3rd body weight in gear (a human with 50 lbs of stuff) to around 25x body weight in gear (a pixie with 12.5 lbs of stuff).

**Realistically, flying is likely less efficient than walking/running, but as GURPS doesn't treat flyers as requiring more food, neither will we.

NecroEDIT: Was thinking on and opted to revisit this recently. It occurs to me that, given roughly equal levels of activity, the "doing stuff" part of necessary food expenditure simply scales linearly with BL, and thus with the square of ST. Given ST scales linearly with height, this makes things easier - if the character's ST is equal to 5x(height in yards), they require 3*(ST^2)/100 standard (~1000 kcal) meals per day. If the character's ST differs from the above, necessary consumption is the average of 3*(ST^2)/100 and 3*((5*height)^2)/100. For an ST 5, 0.3 yard tall pixie, that's an average of 0.41 standard meals, or around 410 kcal, per day. For an ST 15, 0.3 yard tall pixie, it's instead around 3.41 standard meals, or 3410 kcal, per day. For an ST 20, 2 yard tall human, that's an average of 7.5 standard meals, or 7500 kcal, per day.