A look at how thru hiking (ketogenically) impacts your size, shape, weight, and composition… or “What Am I Made Of?”
If you’re familiar with thru hiking, you’re familiar with the infamous before and after photos: a hiker stands at the southernmost terminus of the Pacific Crest Trail, or at Springer Mountain on the Appalachian Trail, looking clean and eager and energetic for the adventure they know begins with their next step. To the left, that same (often barely recognizable) hiker stands at a Northern Terminus looking… less clean… and often tired… and like they’ve gone through a number of extensive physical changes.
We marvel at the “clean-shaven to lumberjack-beard” transition (of men), and the “twigs to calves-of-steel” transition (for everyone). These photos inspire thousands of next year’s thru-hiking class with their incredible transformations, not just physically but also, the on-looker imagines, mentally as well.
(via The Trek)
What we, the viewer, also notice is how thru-hiking can RAVAGE some bodies. Hiking 20-30 miles per day for months at a time draws down on one’s fat stores at a rate that can be impossible to balance with normal nutrition. Hikers can finish lean and “Greek god-like”, or they can fly home emaciated and underweight. The strategies for squeezing more and more calories into one’s hiker menu vary from packing olive oil in to-go containers to eating jars of peanut butter or consuming four pints of Ben & Jerry’s in every town (Johnny, I hope your arteries recovered from that particular dietary coping mechanism).
As I prepared for my 2017 thru-hike, I wanted to document not only the process of a ketogenic backpacking adventure, but also how keto, and thru-hiking in general, impacted my body’s composition. Not satisfied with just before and after photos, I scheduled a full DEXA scan a few days before my trail date, and another a few days after I returned.
What is a DEXA scan?
DEXA means “dual-energy x-ray absorptiometry”. I had to google that. All you need to know: it’s a ~10 minute head to toe scan using a very weak X-ray to determine the composition of every square inch of your body. You make an appointment (costs between $40-$50), lay on a fancy-looking table for a few minutes, and the machine spits out your total body composition, including total body fat percentage and a complete visualization and analysis of your lean tissue and bone density. In other words, it shows you what you’re literally made of.
I’d heard the horror stories of bodies wasting away on trail, and the DEXA scan seemed like a fantastic way to quantify my misery. How much fat was too much fat to lose? Was I losing bone density? Would my arm muscles wither away? Did my ketogenic diet have a negative impact on my body composition?
Time to find out.
Before & After Ketogenic Thru Hiking
Body Fat %
Guess what, I got lean. I went from the 40th-60th percentile of women to the 0-20th percentile, which feels about right with how I felt before and after: “average” to “extremely fit”.
Surprisingly, despite all the stories about how much weight people lost on trail, I only lost 11.7 lbs. Some of my hiker friends dropped as much as 100 lbs, though to be fair they had more to lose than I did to begin with. Still, I felt sure that I’d walk off the trail down at least 20 lbs from the sheer caloric burn of it all (not to mention the ketogenic factor of using my body’s fat supplies as its primary fuel). In reality, my body made very efficient use of the fat stores at its disposal and I put on enough muscle to balance out the decrease in body fat so that the scale didn’t budge significantly. For context: at 5'7", I am not a short lady, but my beginning weight certainly put me in the "fluffy" category.
Fat Tissue (lbs) and Lean Tissue (lbs)
The total weight of the fat tissue in my body decreased from 53.5 to 36.3 and my lean (muscle) tissue increased from 113.8 to 119.6. Ah, so here we start seeing a bit more of the transition/trade-off of fat to muscle: during the trek I lost 17.2 lbs of fat and gained 5.8 lbs of muscle.
Just the numbers please.
Tired of reading those recipe sites that describe how soft the light was when the original chef decided to cut the basil from their own backyard and [scroll] [scroll] [scroll] and "oh look, here's the recipe." Well, here's the before and after, just by the numbers. Enjoy. (TL;DR: I lost a ton of fat in my boobs and butt. Le sigh.)
So, should you keto thru-hike?
Thru hiking did not destroy my body. I completed the trek well within the healthy norms for my height and weight and felt great after I returned home. Thru hiking will absolutely get you into the best shape of your life: I remember moments where I would be in the middle of the day, on ordinary terrain in an unnotable location, and I could feel my leg muscles move powerfully through each step, and my ankles navigate rocks and branches without rolling, and my calves… well, they were always that massive (le sigh). I had a tiny moment of surprise and awe: surprise in how strong I had become, and awe that my body was capable of it this entire time.
Once I returned home and the hiking stopped, it was a struggle to hold onto that level of physical fitness. It took a few weeks for my hiker hunger to subside, and without being balanced out by burning 5000+ calories each day, hikers inevitably put on a few pounds. My body has since settled into a happy middle ground between the “fluffiness” before and the lean athlete after, though I’m looking forward to my next thru hike to reach that level of fitness again and be reminded of the capabilities of my own body.
I am not a doctor. All I can do is speak to what happened to my body, and report on what the scans told me. The data provided in this post is for informational purposes only and is not meant to be used for any type of medical diagnosis. Should you have any concerns about DXA scans or the metrics they provide, please consult your physician.