Reindeer herders from subarctic Finland exhibit high total energy expenditure and low energy intake during the autumn herd roundup

Objective: High levels of total energy expenditure (TEE, kcal/day) have been documented among numerous human populations such as tropical climate horticulturalists and high-altitude agriculturalists. However, less work has been conducted among highly physically active cold climate populations. Methods: In October 2018, TEE was measured using the doubly labeled water (TEEDLW, N = 10) and flex-heart rate methods (TEEHR, N = 24) for 6–14 days among reindeer herders (20–62 years) in northern Finland during an especially physically demanding, but not seasonally representative, period of the year for herders—the annual reindeer herd roundup. Self-reported dietary intake was also collected during TEE measurement periods. TEE was then compared to that of hunter gatherer, farming, and market economies. Results: During the herd roundup, herders expended a mean of 4183 ± 949 kcal/day as measured by the DLW method, which was not significantly different from TEEHR. Mean caloric intake was 1718 ± 709 kcal/day, and was significantly lower than TEEDLW and TEEHR (p <.001). Herder TEEDLW was significantly higher than that of hunter gatherer (p =.0014) and market (p <.0014) economy populations; however, herder TEEDLW was not different from that of farming populations (p =.91). Conclusion: High TEE and low caloric intake among herders reflect the extreme demands placed on herders during the annual herd round up. Although TEEDLW was similar between cold climate herders and hot climate farming populations, there are likely differences in how that TEE is comprised, reflecting the local ecologies of these populations.