The authors rescaled dataset from Ruf and Geiser (2015) in new way – instead of using minimum metabolic rate at hibernation they used daily energy expenditure of hibernation as more meaningful for energy saving hypothesis of hibernation . It is interesting that daily energy expenditure of hibernation scales isometrically with body mass and showed that the theoretical mass at which the savings by hibernation become zero is 75.2 kg

The work concerns an important subject, especially from the point of view of physiological ecologists.
However, in our opinion the manuscript has some deficiencies that can be amended.
1) The text lacks several important information in methods, such as, several technical aspects of the statistical analyses. It is not clear what statistical program and methods were used.
2) Even though the authors correctly underlie in Introduction the strength of their approach, maybe it would be helpful to mention the costs of awakening from the hibernation already in introduction? Reheating and restarting all the processes surely cannot be neutral?
3) In our opinion the text is not clear in many places and requires many small amendments.
4) All in all, the topic of potential human hibernation which is recurring throughout the work, albeit inspiring and eye-catching, is more suitable for a popular science article than a scientific manuscript, unless the aim of the work presented is explicitly to find a way to allow humans to hibernate. The title is already eye-catching and we think that the part of potential human hibernation can be omitted.
5) The part of discussion “Q10, isometric scaling and hibernation” is not really introduce – we suggest to move it to methods part as it is not the question of the paper.

Specific comments

Lines 33-35 - I think this sentence is not phrased correctly. As it is now, it appears to state that a cell of a bat consumes energy at the same rate as an entire bear.

Line 56 - "reduced to 98% of normal levels" means that the energy savings are only 2% of the original value. I think what the authors meant to say was "reduction by 98% of normal levels" or "98% reduction".

Line 59 - one sentence refers to the same unit of measure twice, but the "day" is abbreviated to "d" only in one of these references. Unless it is a deliberate strategy of introducing the unit to the reader, I would suggest settling on a consistent unit referral.

Line 67 - again, "by as much"

Line 112 - this is the third notation of the same measurement unit (kJ / day, kJ / d, kJ d-1). Other units have different notation as well.

Line 112 - although it is quite easy to figure out the meaning of the abbreviation "MB", it would be helpful to spell it out in the text nonetheless. In particular, it should be stated if the value represents the mass before hibernation, after awakening, or maybe average of the two?

Line 120 - what does "fat consumption" stand for? The amount of fat the animal loses during the hibernation? Stated like this, it suggests a measure of the amount of fat in the food the animal consumes when it is not hibernating.

line 133 - missing space before "p=0.002"

line 150-151 - this sentence is missing a verb.

line 236-237 - The example of a polar bear is not the best, as it is quite widely known that in this species does not routinely hibernate. Perhaps it would be better to stick to the two bear species represented in the calculations and on fig. S3. I would also argue with the statement from line 237 referring to bears as "large carnivores" - whereas this can be true for polar bears, in lower latitudes the bears are predominantly omnivorous.

line 236-237 - Missing word, perhaps "hibernation of these large carnivores" or "hibernation in these large carnivores".

line 239 - incorrect grammar, "do" is missing from the question

line 296 - I would suggest replacing "whose slope" with "the slope of which"

line 300 - unnecessary comma

line 307 - The subchapter names are inconsistent - sometimes they take form of a sentence ("Why do bears hibernate?"), sometimes a form more fitting a bullet point list ("Minimum cell metabolism"). I am not sure to which category would "Human hibernation?" qualify.

Fig s2. In description it is written “The datapoint at MB=80 kg corresponds to a black bear”. It would be better to mark it on the graph.

Data in repository
The data available in repository contains only raw data, but not the code used for statistical data analysis and full outputs of results from the analysis, which would be also valuable.