Exploring the Evolutionary Disparities: A Case Study on the Psychophysiological Response to Recreating the Hunter–Gatherer Lifestyle through Physical Activity and Caloric Restriction

Round 1

Reviewer 1 Report

The manuscript of Belinchón-deMiguel et al. is a well-written manuscript, with clear scopes and well-structured results.

However, I have some points that need further changes/discussion.

Delete two .. in lne 27

You have to explain how was the sample chosen? It seems convenient, was it biased?

Consider adding information about the exact calories of the two participants, as well as some details about the meals. It might be something that other researchers would like to try.

Thank you.

Author Response

The manuscript of Belinchón-deMiguel et al. is a well-written manuscript, with clear scopes and well-structured results.

Thank you for your words

However, I have some points that need further changes/discussion.

Delete two .. in lne 27

corrected

You have to explain how was the sample chosen? It seems convenient, was it biased?

it was explained "Due to the inherent challenges associated with sourcing participants for extreme events, a convenience sampling method was employed for this study. Only two participants were selected based on their availability, willingness, and capability to partake in the high-intensity activities required by the research. This non-random selection was deemed necessary because of the distinct nature of the events under investigation and the difficulties encountered in recruiting suitable participants with the specific expertise and resilience needed for such intense scenarios. It is important to note that while convenience sampling offers certain advantages in terms of feasibility for unique studies like this, the results may not be generalizable to the broader population due to the potential biases associated with this sampling technique. However, the insights garnered from these two participants provide a valuable starting point and can guide more extensive, future research endeavors in this niche area."

Consider adding information about the exact calories of the two participants, as well as some details about the meals. It might be something that other researchers would like to try.

These data were included in participants sections and table 3

Thank you.

Reviewer 2 Report

In this study, the authors tend to identify the physiological changes due to hunter-gatherer lifestyle with two participants (1. Starved and 2. Control) and their role in health. The studied psychophysiological parameters include body mass, cortical arousal, hand-grip strength, lower limb strength, heart rate variability, reaction time, hydration status, blood glucose, and lactate levels, urine markers, sleep quality, pain perception, stress levels, perceived exertion However, the manuscript needs major revision before publication.

Comments

 In the Abstract, do not use acronyms instead use abbreviated words. CK full form was missing.

The following sentence is not scientific “Some authors have argued that humans are the only animals that consume energy 51 without prior expenditure, thereby breaking biological laws (5)”. You could say “Taylor et al., 2016 indicated that humans are the only animals consuming energy without prior expenditure, violating the biological laws (5).”

Could the author explain ‘why one participant was starved while the other was not’ in the discussion?

Also, I believe you could have also monitored a normal individual who does the regular lifestyle or at least discussed the comparison between a regular individual and a test group.

I could see that both participants' weight were reduced compared to the initial weight, Is it due to increased physical activity? Authors suggested that the Hunter-Gatherer lifestyle may help to maintain health but a decrease in body weight might also be due to various factors.

Why select Male participants only?

I think the initial study with the animal model would increase the scientific soundness or discuss more with previous animal model studies.

Don’t authors think of inclusion and exclusion criteria for the participant section?

A minor grammar check is required. For example, punctuation misuse, additional spaces or no spaces between words, unclear sentences, etc...

Author Response

In this study, the authors tend to identify the physiological changes due to hunter-gatherer lifestyle with two participants (1. Starved and 2. Control) and their role in health. The studied psychophysiological parameters include body mass, cortical arousal, hand-grip strength, lower limb strength, heart rate variability, reaction time, hydration status, blood glucose, and lactate levels, urine markers, sleep quality, pain perception, stress levels, perceived exertion However, the manuscript needs major revision before publication.

Comments

 In the Abstract, do not use acronyms instead use abbreviated words. CK full form was missing.

It was corrected

The following sentence is not scientific “Some authors have argued that humans are the only animals that consume energy 51 without prior expenditure, thereby breaking biological laws (5)”. You could say “Taylor et al., 2016 indicated that humans are the only animals consuming energy without prior expenditure, violating the biological laws (5).”

Corrected

Could the author explain ‘why one participant was starved while the other was not’ in the discussion?

The decision to have one participant undergo fasting while the other did not was intentional and designed to simulate the inherent variability and unpredictability of the hunter-gatherer lifestyle. It was common for hunter-gatherers to face days of feast and famine depending on the success of their hunting or gathering activities. By having one participant fast while the other did not, we aimed to explore a broader spectrum of the evolutionary lifestyle - from periods of relative abundance to those of scarcity. This approach was chosen to provide a more holistic understanding of how such disparate conditions within the same overarching lifestyle could differentially impact psychophysiological responses.

In future research, we plan to expand the number of participants and possibly include varied caloric restrictions to further delve into the nuances of these evolutionary disparities.

We appreciate your insightful query and hope this explanation provides clarity. We will ensure that this rationale is explicitly outlined in the discussion section to ensure comprehensive understanding for all readers.

Also, I believe you could have also monitored a normal individual who does the regular lifestyle or at least discussed the comparison between a regular individual and a test group.

We acknowledge that incorporating a participant representing a regular modern lifestyle could have added another layer of depth to our comparative analysis. Such an inclusion would allow for a clearer juxtaposition between the hunter-gatherer recreation and contemporary sedentary behaviors, elucidating the distinct psychophysiological disparities between them. The difficulty in recruiting participants in this extreme event precluded a large sample. In retrospect, we agree that this would have been beneficial, and your feedback has provided us with a constructive avenue for future studies. We will ensure to discuss the potential outcomes and implications of such a comparison in the discussion section of the paper. This will help highlight the potential differences and provide a contextual framework for readers unfamiliar with typical modern-day psychophysiological parameters.

I could see that both participants' weight were reduced compared to the initial weight, Is it due to increased physical activity? Authors suggested that the Hunter-Gatherer lifestyle may help to maintain health but a decrease in body weight might also be due to various factors.

You're absolutely right; the decrease in body weight can arise from multiple factors, and it's essential to discern the specific contributions to such a change. While the increased physical activity during the study is one significant factor, other elements, such as caloric restriction (especially for the fasting participant), dehydration, and potential loss of lean body mass, could also contribute to the observed weight loss.

In the context of the Hunter-Gatherer lifestyle we aimed to recreate, such weight fluctuations might be representative of the natural ebb and flow experienced by our ancestors, where periods of caloric abundance alternated with times of scarcity.

To provide more clarity on this, we will delve deeper into the contributing factors behind the weight reduction in the discussion section, considering not only the increased physical activity but also exploring other parameters like hydration status, muscle mass retention, and energy expenditure.

Your feedback helps us improve the depth and precision of our analysis. We genuinely appreciate it and will refine our manuscript accordingly.

Why select Male participants only?

we explain participant selection in participants section and included this fact as a limitation and future research

I think the initial study with the animal model would increase the scientific soundness or discuss more with previous animal model studies.

While we recognize and appreciate the value that such studies can bring in understanding physiological mechanisms in a controlled environment, our current research facility does not have the infrastructure or resources related to animal laboratories. This limitation precluded us from initiating preliminary investigations using animal models. However, in light of your feedback, we will expand our discussion to integrate and contrast our findings with existing literature on animal model studies, providing a contextual backdrop and drawing parallels where applicable.

Don’t authors think of inclusion and exclusion criteria for the participant section?

They were included

Round 2

Reviewer 2 Report

Authors have addressed all the suggested queries and updated the manuscript. I recommend the manuscript for publication.