Category: Research

Very proud to share this new article written by the newly minted Dr. Alexandra Niclou (my now former PhD student).

This work looked at brown adipose tissue activation between summer and winter among folks in Albany, New York. We compared changes in metabolic rate, respiratory quotient, & supraclavicular heat dissipation between room and mild cold temperatures in summer & winter. The participant pool was largely the same between the two seasons.

During cold exposure – when brown fat is activated – supraclavicular temperatures were greater in winter compared to summer while metabolic rate did not change. RQ – an index for substrate utilization – significantly increased in winter compared to summer, suggesting increase in preference for carbohydrates as fuel in winter.

This demonstrates that inferred brown fat activity is greater, more efficient, & increases glucose use in winter. Brown adipose tissue may play a role in seasonal cold acclimatization and glucose disposal in humans.

First paper of 2022 came out today in the International Journal of Circumpolar Health! For this paper we looked at potential associations between body mass index and body adiposity with cholesterol and glucose levels among a small sample of reindeer herders in sub-Arctic Finland.

Despite over 70% of the herders being classified as having obesity or being overweight, blood biomarkers were largely normal. Though total cholesterol was high, this appears to be largely driven by high HDL cholesterol levels. Furthermore, glucose levels were also relatively normal.

Though the sample size is small, there does not appear to be a strong correlation between BMI, body adiposity and some indicators of cardiometabolic health, which has been seen among other populations.

This adds further evidence that using BMI and its health correlates as a diagnostic tool is not particularly helpful especially as the individual level.

Furthermore, as the reindeer herders are highly physically active and have a variety of cold climate adaptations, we could be seeing a demonstration of the fat and fit (and cold) hypothesis playing out.

I am excited to share our new publication about Reindeer Herder total energy expenditure (TEE, kcal/day)! This work is the result of a collaboration with Dr. Päivi Soppela, Dr. Minna Turunen, Ville Stenbäck, Dr. Karl-Heinz Herzig, Dr. Rebecca Rimbach, and Dr. Herman Pontzer. We measured how many calories the reindeer herders in sub-Arctic Finland expend and consumed during an exceptionally busy time of year…the autumn herd roundup. We also included some pilot data from a much less busy time in the spring.

The herd round up consists of collecting reindeer from their summer pastures either on foot or with the aid of all-terrain vehicles, motorbikes, snowmobiles, or helicopters. During this time, herders count the number of reindeer, separate the animals to be left alive from those to be slaughtered, mark calves with the owner’s earmarks, and return any wayward reindeer to their proper owners.

Here are some of the key findings:

Herders are very active during the annual herd roundup!

We measured TEE using two methods: the gold standard doubly labeled water technique and the flex-heart rate method. During the herd roundup, herders expended a mean of 4183 ± 949 kcal/day with female TEE ranging from 2898-3887 kcal/day and male TEE ranging from 3463-5853 kcal/day. There was no significant difference between the two methods.

Herders eat way fewer calories than they burn during the roundup, and their diet is relatively high in fat.

Females consumed 883-2195 kcal/day and males consumed from 854-3638 kcal/day, which is well under the number of calories they were burning each day. Diet information was collected via diet diaries, and this can be a rather inaccurate estimate of calories consumed. However, even if herders underreported calories by as much as 20%, they still would have expended ~1000 kcal more than they were consuming each day during the herd roundup. The herders’ diet consisted of a greater proportion of protein and fat than is recommended by the World Health Organization (WHO).

Herders expend a similar number of calories to farming economy populations like the Aymara speaking peoples and Shuar…at least during the herd roundup.

We compared the herder total energy expenditure to that of hunter-gatherers, farming economy populations, and market economy populations. Herder TEE was significantly higher than hunter gatherer and market economy populations, but very similar to that of the farming populations. However, herder TEE was much lower during the spring pilot study, though May is a particularly less busy time of the herder year.

Given exposure to extreme cold in addition to high physical activity levels, one might expect herder TEE to be significantly higher than, rather than equivalent to, equatorial farming economy populations with similar activity levels but a potentially reduced thermoregulatory burden. There are several potential explanations for the similar energy expenditure among the herders and the farming economy populations, all of which highlight how local ecologies and biologies likely play an important role in shaping energy expenditure.

1. Herders are very good and very experienced at mitigating cold stress – using technology, alternating tasks, and eating warming foods, for example.
2. The herders’ high levels of physical activity may help reduce the cost of trying to stay warm in their cold climate.
3. The farming economy populations are also known to carry a high parasitic burden (though cold climate populations have their fair share of such burdens, too, though not to the degree of equatorial populations). This high parasitic burden can raise energy expenditure in the way that the need to keep warm may raise energy expenditure among the herders.

What’s Next?

Well, we are applying for funding in hopes of expanding TEE measurements across seasons to get a better, more detailed view of energy expenditure across the herder work year. We would also like to expand the number of participants, and begin to look at the impact of climate change on reindeer herder TEE and other physiological measures.

Real Clear Science did a nice write up of our new Neanderthal biocultural cold adaptation review paper!

I really love this piece, and it delights me to see it get a tiny but of traction.

My review paper on Neanderthal biocultural adaptation to cold (email me for a copy), written with the amazing Dr. Sarah Lacy and Alexandra Niclou, came out today!

This paper was born out of a poster (link to file below) I and Alex made for a special American Association of Physical Anthropology poster session held to celebrate Dr. Erik Trinkaus‘ career. It was a wonderful session that gathered together all of his students.

For this poster, we wanted to talk about the different mechanisms that may have been utilized by Neanderthals to survive and thrive in cold climates. While making this poster, we realized that there was no paper that brought together the anatomical, physiological, and cultural evidence of Neanderthal cold climate adaptations. So, we decided to write one! We brought my friend, colleague Sarah Lacy in on this as Neanderthals are her area of expertise, and we got to work!

This paper puts in one place the variety of different cold climate adaptations Neanderthals may have had. Furthermore, we identify ten different areas we think should be the focus of future research.

I adore this paper for many reasons:
1. This paper provided the opportunity to collaborate and write with two brilliant women who I adore. Writing with them was a joy, and we worked incredibly well together.
2. The the image of Neanderthals and Anatomically Modern Humans depicts females…such a rare thing. This figure was also drawn by an undergraduate student of mine, Morgan Zepf.
3. It has an awesome reference list! The original draft had 275 references, but had to cut that down to 100 to fit the journal guidelines.
4. This will be a great paper to use in undergraduate classes!
5. We hope this paper will guide and inspire future dissertations.
6. I started writing this review on my Spring Break 2020 where I went to a cabin in the middle of no where and just wrote. When I emerged from this writing retreat, the entire world had gone on lock down due to the COVID-19 pandemic. This paper will always hold an odd place in my memory because of that.