Measuring and Predicting Total Energy Expenditure Among Highly Active Humans in Natural Environments
Date of Award
Doctor of Philosophy (PhD)
Chair and Committee
The current model for predicting human total energy expenditure (TEE), the Factorial Method, significantly underestimates actual TEE, particularly among highly active populations. In this study, the Allocation Model is presented for predicting TEE. Unlike the Factorial Method, the Allocation Model includes metabolic cost terms for both thermoregulation and the thermic effect of food, as well as using more accurate basal metabolic rate and activity cost estimations. The Allocation Model was tested using doubly labeled water and flex-heart rate measured TEEs of healthy, highly active adults (N=56) participating in National Outdoor Leadership School semester long courses. Two of the semester-long courses took place in both hot and temperate climates and the other two in both temperate and cold climates.
The Allocation Model produces TEE predictions that are not significantly different from measured TEE values. Overall, the Allocation Model comes within 12% of measured TEE values. The Allocation Model also comes within 10% of measured TEEs greater than 3500 kCal day-1 compared to a 30.2% underestimation by the factorial method. This analysis demonstrates that the Allocation Model is more accurate at TEE prediction than the Factorial Method across a range of activity levels and in different climates. Furthermore, the Allocation Model succeeds where the Factorial Method has failed - at high levels of energy expenditure. The Allocation Model can also be used to better understand how energy is allocated under different climatic and activity level conditions. From this, it was found that in cold conditions, the heat produced from activity helps to mitigate potentially high costs of thermoregulation. I was also able to analyze the relationship between the surface area/mass ratio and energy expenditure in the different climates. This allowed me to determine whether an energetic advantage of Bergmann's and Allen's rules was present among the NOLS population. In this study it was found that a greater surface area/mass ratio provided an energetic advantage in hot climates. However, there is also evidence that a greater surface area/mass ratio is advantageous for heat dissipation in cold environments in individuals wearing heavily insulated clothing.
The results presented here suggest the Allocation Model is a powerful new tool that should be used in place of the Factorial Method for estimating human TEE, and can be used to analyze adaptations, life history strategies and differential energy allocation among highly active humans in natural environments.
Ocobock, Cara, "Measuring and Predicting Total Energy Expenditure Among Highly Active Humans in Natural Environments" (2014). All Theses and Dissertations (ETDs). 1257.
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Permanent URL: http://dx.doi.org/10.7936/K7MW2F4Q