Organisms with high metabolic rates often have inefficient energy production due to unsaturated fats in their membranes.

“these organisms that have the high metabolic rate they don't have a really efficient metabolic rate they have a very inefficient capacity for energy production this is because they have more unsaturated membranes they have more polysaturated fats in the membranes of their mitochondria of the plasma membranes and so they waste so much energy dealing with this dealing with you know restoring the sodium pottassium gradient and trying to produce ATP when there's you know they can't do it as efficiently”

“but then I also mentioned permeability to other ions like sodium and potassium and the sodium and potassium gradient is also incredibly important to be maintained between the intracellular and extracellular space and so when we're leaking the sodium and potassium through we then have to waste a bunch of ATP pumping that back and maintaining that gradient and these two things together account for a massive shift in the efficiency of energy production when we have more polyunsaturated fats versus less polyunsaturated fats”