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If a human body were somehow to be kept at a cold temperature (say 30C) for the entire life of the given individual. And somehow the brain could be fooled into thinking that this 30C feels nice and warm.

Would that given individual live longer as a consequence? What effect does a tempreature have on lifespan?

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    $\begingroup$ A core temperature of 30°C? That's right on the edge of severe hypothermia, I wouldn't expect it to be a survivable condition for too long. Especially for neonates if you wanted to maintain the temperature from birth. $\endgroup$
    – Rory M
    Dec 27, 2012 at 13:18
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    $\begingroup$ okey then, 32. Could even keep them a bit warmer in the beginning. $\endgroup$
    – john-jones
    Dec 27, 2012 at 13:41
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    $\begingroup$ As a flypushing biologist I know that if I want my flies to live longer I keep them at 18 degrees C, rather than the normal 25. Not sure if any work has been done to understand the mechanisms and whether or not these mechanisms would apply to larger organisms. $\endgroup$
    – rg255
    Dec 27, 2012 at 14:52
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    $\begingroup$ Epic, so u just put them in the fridge like food u want to last longer? How much longer do they live at 18c compared to 25c? $\endgroup$
    – john-jones
    Dec 27, 2012 at 14:55
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    $\begingroup$ And frogs are relatively advanced animals, there are those who can just freeze in the autumn and thaw back in the spring: youtube.com/watch?v=Fjr3A_kfspM $\endgroup$
    – john-jones
    Dec 28, 2012 at 10:10

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I am assuming that you are referring to a baseline human cooled to a core body temperature of 30C from birth. I am also assuming that you are ignoring the fact that the environmental temperature (and thus the temperature of the extremities) has to be much lower than 30C to cause a core temperature of 30C. Thus, I am ignoring hypothermia-based gangrene, necrosis, and extremity loss.

If you had a normal human with a 30C core temperature starting at birth, I have doubts that it would live any longer than a human at 36.8C. Unlike flies, which are ectotherms, humans need to have a more or less constant temperature to successfully complete most of their metabolic processes efficiently. Since humans are not built to withstand extremely low temperatures, it is likely that lowering the core body temperature to 30C will cause it to have organ impairment, causing organ failure, followed by death. Though you might be able to "fool" the brain on thinking that 30C is normal, it is unlikely that the organ functions can follow. It could be possible to breed successive generations of humans in ever-lower temperatures, but it is unlikely for a baseline human to withstand such a large temperature drop. Sensory neuron adaptation =/= bodily adaption. However, lowering the core human body temperature by 1-2 degrees (typical of sleep) may have a chance of altering a human's lifespan in a more meaningful way. Though cooling may prolong the lifespan of temperature-conformers and single-celled animals, it is unlikely that the same can be said for endotherms. Endotherms have had biological processes that run on a fixed temperature for a long time already. One more thing: @Hermann: Their core body temperature may not have been much lower than the baseline.

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    $\begingroup$ Nice (up-voting that answer!), I was thinking more about this on my run this morning, and I agree with you - flies do not regulate their temperature internally and are adapted to survival within normal temperature fluctuations. Humans on the other hand use homeostasis to maintain a core temp of 37(ish) degrees, and when that drops the body actively tries to warm it self up. I think this could actually decrease lifespan because it would increase metabolic stress (more calories are required to survive). $\endgroup$
    – rg255
    Jan 6, 2013 at 12:32
  • $\begingroup$ Another argument for cold-induced longevity is that I know a person who's been working at the ER for decades, and she says people who die in extreme circumstances, such as drowning in sub zero water, can be brought back after unbelievably long amounts of time with far less damage than when in normal temperatures. Indicating the temperature is slowing things down. $\endgroup$
    – john-jones
    Jan 8, 2013 at 13:28
  • $\begingroup$ I agree though that if the body is constantly trying to raise the temperature then that should increase metabolic processes and thus probably shorten lifespan. But if the brain could be fooled into thinking this lower temperature is the nice new norm.. $\endgroup$
    – john-jones
    Jan 8, 2013 at 13:47
  • $\begingroup$ "Since humans are not built to withstand extremely low temperatures, it is likely that lowering the core body temperature to 30C will cause it to have organ impairment, causing organ failure, followed by death." Are you sure about that? The Icelander who swam for 6 hours in the 5c ocean, surely had a core temperature below 30c, and he was fine. $\endgroup$
    – john-jones
    Jan 9, 2013 at 0:28
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    $\begingroup$ @ Hermann Ingjaldsson. Core body temperature is maintained at all cost. Including shutting down circulation to the skin, and limbs. The moment core temperature is affected, the brain slows down, heart beat diminishes, breathing slows, even stops. And organs start shutting down. $\endgroup$
    – JayCkat
    Dec 26, 2016 at 22:27
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In humans the optimal temperature for enzymatic action is 37 C. See the image below: enter image description here

Our body temperature is set at 37 C (~ 97 F) because all our metabolic processes are most efficient at this point. Any decrease in the core temperature will cause a drop in all the metabolic processes imitating hypothyroidism. Hypothyroidism is a very unpleasant condition to live with - extreme fatigue, inability to utilize the energy stores, very poor appetite with increasing fat stores are few of its symptoms.

For humans to efficiently operate at lower temperature the DNA has to be remade to code for enzymes that would not loose their efficacy at a lower temperature - maintaining a good reaction rate. This is impossible as of now where even a single gene modification or single nucleotide correction is extremely difficult and is under experimentation.

Source: https://sachabiochem0001.wordpress.com/2013/04/09/factors-affecting-enzyme-activity/

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Movement is life. If the human body where to undergo this kind of temperature that would be below the normal temperature for the human body, we would in fact either have to move more and or do more as in eat, exercise, communicate etc. If your body did not have this mental capacity basic survival skill you would be in the process of slowing the function of your body down leading to death.

Also the person who had swam in freezing water had a better tolerance to the cold than normal, but this does not mean that if a person had the capacity to tolerate cold temperatures that this kind of treatment of the body whould be good for you. Over a short period of time your body can undergo extream circumstamces so it was a basic survival skill that had kicked in from the metal material of that persons being telling their physicsal as in nervous system that if they were going to survive they would have to move in order to regulate their body temperature.

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