Energy expenditure and activity among Hadza hunter-gatherers.
Level 4 - case-series / case-control
Cross-sectional observational study without a concurrent control group
PubMed 25824106 · doi:10.1002/ajhb.22711
What was done
Researchers measured physical activity and energy expenditure among 41 adult Hadza hunter-gatherers across two camps in northern Tanzania during normal daily life. Wearable GPS units tracked daily walking distance and walking speed. In a subset of 30 adults, doubly labeled water was used to measure total energy expenditure (TEE), alongside workload indices (foraging return rate, maternal status, number of dependent children) and urinary biomarkers of metabolic activity and stress (8-hydroxydeoxyguanosine, cortisol, and testosterone).
What was found
Fat-free mass was the single strongest predictor of TEE (r² = 0.66, P < 0.001). Men had greater daily walking distances and faster walking speeds than women, but neither sex nor any metric of physical activity or workload correlated with TEE after controlling for fat-free mass. Hadza adults had TEE comparable to developed, industrial populations, alongside elevated 8-hydroxydeoxyguanosine levels. Specific numerical values for walking metrics, total calories, and biomarker concentrations were not reported in the abstract.
Why it matters
These findings suggest that total daily energy expenditure does not scale directly with physical activity in highly active populations, supporting models where humans adapt to high activity by reducing energy allocation to other physiological processes.
Limits
The sample size is small (n = 41 total, n = 30 for doubly labeled water) and drawn from a single traditional population. The cross-sectional observational design cannot establish causality, and absolute values for physical activity, energy expenditure, and biomarkers were not provided in the abstract.
Cited by
- supports Hunter-gatherer populations typically walked approximately 7 to 10 miles (about 14,000 steps) per day.