Adaptations and Energy Requirements in Backcountry Hunting

[Becca]

Many of you know Larry Bartlett of Pristine Ventures in Fairbanks. He presented at the AK SCI last weekend on a study he helped conduct at the University of Alaska Fairbanks last summer regarding caloric expenditures and caloric intake on backcountry hunts. I was unable to attend in person, so I was thrilled to find it available to view online. I hope some of you enjoy it, as I did. Although a little heavy on the science (which I loved), I expect even non-science geeks will enjoy the videography and sense of humor we've all come to enjoy from Larry.

As someone who has spent a fair amount of time calculating calories to carry for backcountry hikes, floats and backpack hunts I found this study fascinating. I knew I probably burned more calories than I was taking in on backcountry trips, and that I come home feeling "healthier" but this is the first time I've seen someone objectively document the physiologic effects of backcountry activities on the body.

 

[Becca]

For anyone interested in the paper they published documenting the study and their findings, here it is:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6236107/

 

[Ryan Avery]

I was just about to post this. Larry is a stud!

 

[Becca]

I was just about to post this. Larry is a stud!

Yep, without question! Just watching him drag that sled around makes me tired.

 

[AKDoc]

Larry is the real deal for sure...I appreciate his contributions to the world of Alaska back country hunting, fishing, and pack-rafting...and his support of fellow veterans.

 

[JWP58]

Very interesting research project! I'm extremely surprised on the complete lack of muscle loss with prolonged caloric deficiency at the rate of 2500kcals a day. Cool stuff for folks that are into exercise physiology.

 

[Becca]

Very interesting research project! I'm extremely surprised on the complete lack of muscle loss with prolonged caloric deficiency at the rate of 2500kcals a day. Cool stuff for folks that are into exercise physiology.

Me too! In counting calories consumed, i've long known that Luke and I struggle to consume more than 2,600-3,000 calories per day on backcountry trips. Even when we carry more, we rarely eat it and so we've stopped carrying the excess weight. I found it fascinating that muscle mass was maintained even with the calorie deficit, almost like our bodies get more efficient with prolonged, sustained activity.

 

[S.Clancy]

Me too! In counting calories consumed, i've long known that Luke and I struggle to consume more than 2,600-3,000 calories per day on backcountry trips. Even when we carry more, we rarely eat it and so we've stopped carrying the excess weight. I found it fascinating that muscle mass was maintained even with the calorie deficit, almost like our bodies get more efficient with prolonged, sustained activity.

It's always amazing how many calories are actually burned. When I was 21 working trail crew out of Red Lodge, MT I tracked my calorie consumption over a couple weeks. I was consuming around 7000 calories a day and still slowly losing weight. Pretty unreal that I wasn't reaching maintenance with that intake.

 

[Becca]

It's always amazing how many calories are actually burned. When I was 21 working trail crew out of Red Lodge, MT I tracked my calorie consumption over a couple weeks. I was consuming around 7000 calories a day and still slowly losing weight. Pretty unreal that I wasn't reaching maintenance with that intake.

Yes, kind of makes you realize how sedentary most of us are compared to historically. Something I found fascinating about Larry and Dr Coker's project was that they were able to objectively measure energy expenditure after the fact by analyzing urine samples from the field. I've found some rough ways to measure calorie burn (HR, perceived rate of exertion, calculators etc) but it's super difficult to figure all the factors on a backcountry hunt (accounting for uphill terrain, thick brush, variable pack weights, etc).

 

[S.Clancy]

Yes, kind of makes you realize how sedentary most of us are compared to historically. Something I found fascinating about Larry and Dr Coker's project was that they were able to objectively measure energy expenditure after the fact by analyzing urine samples from the field. I've found some rough ways to measure calorie burn (HR, perceived rate of exertion, calculators etc) but it's super difficult to figure all the factors on a backcountry hunt (accounting for uphill terrain, thick brush, variable pack weights, etc).

Another thing to consider is ground cover. The difference between on trail and off trail is huge due to the stability introduced by the trail. The same goes for snow cover. Energy expenditure increases rapidly as stability decreases. Something to keep in mind.

 

[william schmaltz]

Thanks for sharing! I didn't get to town until Tyler did his talk and was mad I missed Larry's talk!

 

[AKDoc]

It's a very interesting study. I did a quick read through the paper on the nih website...I'll read it more carefully later and watch the video when I have time. In my quick read I didn't see a description of the total grams of protein in the TEI of the prepackaged meals that were consumed in the study. Did I miss that?

Like you guys, I struggle to meet daily caloric intake when I'm in the field. I always do two and a half to three weeks continuous in the field each September, living in a tent. I force myself to eat three meals, and I try to be mindful of daily protein intake. Despite my efforts, I always return home to see that I lost anywhere between 5-8 pounds. I'm 5'10" and 185, and I work out at the gym with weights three times a week as a baseline.

 

[5MilesBack]

Very interesting research project! I'm extremely surprised on the complete lack of muscle loss with prolonged caloric deficiency at the rate of 2500kcals a day. Cool stuff for folks that are into exercise physiology.

In a 30 day archery elk season I'll hunt about 22 days most years all above 10k feet, and according to my GPS I'll average about 10-11 miles a day. With the combination of the altitude and perhaps just the task at hand, I lose my appetite. I don't eat breakfast (just coffee) and will eat lunch and dinner and maybe a snack in the afternoon. I'm lucky to get 2k calories a day. I'll lose 20lbs over that time and I normally start at around 215-220 at 6'6". By the end of the season, I feel stronger and more ready to go than when I started the season.

 

[JWP58]

In a 30 day archery elk season I'll hunt about 22 days most years all above 10k feet, and according to my GPS I'll average about 10-11 miles a day. With the combination of the altitude and perhaps just the task at hand, I lose my appetite. I don't eat breakfast (just coffee) and will eat lunch and dinner and maybe a snack in the afternoon. I'm lucky to get 2k calories a day. I'll lose 20lbs over that time and I normally start at around 215-220 at 6'6". By the end of the season, I feel stronger and more ready to go than when I started the season.

Well you're the perfect case study! Now you just need to find a motivated researcher at CU or CSU.

 

[Becca]

It's a very interesting study. I did a quick read through the paper on the nih website...I'll read it more carefully later and watch the video when I have time. In my quick read I didn't see a description of the total grams of protein in the TEI of the prepackaged meals that were consumed in the study. Did I miss that?
.

I may be wrong, but I didn't get the impression that they kept the amount of protein consumed consistent. I know it definitely varies from dehydrated meal to meal. I believe they just had the participants track their calories consumed, although they may have been recording protein and or fat content as well.

I think you already said it above, but I am still astounded that they managed to maintain their lean muscle mass while working with a calorie deficit and losing body fat. I wonder if that would remain true over a longer period of time, say months instead of weeks? For most of us, even the busiest hunters don't maintain that level of activity with that kind of a calorie deficit for longer than a few weeks a season at most. Even most guides I know have breaks built into their yearly schedules.

 

[Jimbob]

I am no expert but I am not surprised at all that they maintained muscle mass. Our bodies will use up our fat reserves before starting to break down protein for energy. I just don't see 12 days as being anywhere close to enough time to start breaking down our muscles when we are still eating a good diet.

Interesting study and cool that it involves hunting but I am unsure what questions it is answering.

It would be cool to see what the bodies response to a sustained calorie deficit would be. For instance how long can we maintain minimal muscle mass loss when eating a good diet but burning more calories than consumed? Or what is the threshold of calorie deficit before we start losing significant muscle mass?

For any of these questions to be answered you would need to do a study with way more test subjects (as the paper suggests) and even still it would only be a guide line. Ultimately, you need to figure out for yourself what works.


Having said all that I find the conclusion of the paper pretty funny. "These data further emphasize that obesity in our modern society may simply be an adaptive response to excess nutrient availability relative to modest physical exertion."

Scientist just love to sound smart or complicate things ha ha. I have a degree in Wildlife Biology and I am a science teacher so I have spent a little bit of time in the science world.

 

[AKDoc]

...I find the conclusion of the paper pretty funny. "These data further emphasize that obesity in our modern society may simply be an adaptive response to excess nutrient availability relative to modest physical exertion."

I think the scientific jury has already rendered a verdict on that count...!.

 

[5MilesBack]

My wife goes to the gym and runs and lifts probably 4 days a week. So 2-3 months ago she started the Keto diet. And she's all into it, using some app that tells her what she needs to eat, etc. So after the 2-3 months she says "I haven't lost any weight". Well duh.......that's because you're still eating the same amount of food, just more fat and protein than carbs. 3k calories is still 3k calories........and fat has twice the calories as carbs.

But here's something interesting I've noticed over the years. Outside of extreme exertion for days on end like backcountry hunting in the mountains, my metabolism has always adjusted to how much I'm eating. The less I eat, the slower it goes. The more I eat, the faster it goes. When I was in my early 30's I tried a 7k+ calories a day diet for 6 months. I gained exactly 0 pounds, so went back to my normal (back then) 3-4k a day, and lost 0 pounds.

 

[NW307]

Very cool, real world scientific data and research instead of fad diet and workouts.

 

[AKDoc]

I finally got a chance to read through the article more carefully and watch the video. This study is a meaningful contribution to the field, and I appreciate Becca posting it for our review.

Having a small sample N of 5 is just fine for it's purpose...it's not a study attempting to make an statistically inferential reference to a general population, which would require a minimum N of 30, representative participants.

The liver lipid reduction, post-hunt, across all five participants was a bonus finding. Again, I really appreciate Larry's contributions to our wonderful world of hunting and outdoor pursuits.