You've probably heard the adage that you can't outrun a bad diet. Does the same hold true for hiking? Thru-hiking burns up to 5000 calories per day, and hikers try to meet that demand with lightweight, calorie-dense, and non-perishable foods. Think candy bars, pop-tarts, and pastries. Most thru-hikers finish the trail very lean and ravenous. It can take several weeks for the 'hiker hunger' to settle down even once they get off the trail.
Since hikers make trail meals out of only what they can carry, they usually gorge on pizza, beer, and burgers during zero days in town. Though many would label the typical thru-hiker's diet as unhealthy, most trekkers lose weight and gain muscle during the hike. Thus, they give the appearance of being in better health than when they started. However, a new case study questions whether or not this assumption is valid(1).
An experienced 25-year-old healthy and fit male thru-hiker volunteered to record this physiologic data during his expedition on the Pacific Crest Trail (PCT). Researchers recorded his baseline measurements one week before his hike. The subject used his Garmin and GutHook app to record data on the trail. The researcher's primary interest was in the effects of prolonged exercise on his body measurements and his cardiovascular health. One would typically expect that his cardiovascular health and fitness would improve (although the subject was already quite fit and lean).
One week after his 33-day completion of the PCT, the subject again underwent measurements of his body composition, skeletal health, and cardiovascular function. The change in body weight and BMI were negligible, but researchers noted that body fat distribution changed, with less fat on the arms and legs but more in the trunk despite little change in absolute value. In addition, his arteries were stiffer, and the lining of his vessels was less healthy - both factors that can contribute to heart attack and stroke.
The hiker also experienced a small decrease in his bone mineral density. While his levels of bone density were still within normal, the researcher expressed concern that the areas of bone loss were the spine and pelvis. This area should have become stronger considering the hiker's pack weight and length of time his bones were under load. The researcher points to nutritional deficits as a possible reason for the bone loss.
By all appearances, this hiker finished the trail in as good of shape as he started it. However, the inside of his body experienced changes similar to aging - stiffening of arteries, accumulation of body fat in the trunk, and bone loss. Current research supports an active lifestyle and prolonged exercise to combat these aspects of aging. Therefore, this case study highlights the fact that exercise can only do so much. What you eat is just as important for maintaining optimum health. Older hikers already experiencing these issues may need to pay careful attention to their meal planning to avoid further declines.
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Reference
Physiological Reports. 2021;9:e14767.