Energy expenditure and obesity across the economic spectrum.
Level 4 - case-series / case-control
Cross-sectional comparative observational study across populations (graded by design analogy).
PubMed 40658837 · doi:10.1073/pnas.2420902122
What was done
Researchers analyzed energy expenditure (total, basal, and activity) alongside body fat percentage and body mass index (BMI) in 4,213 adults from 34 populations across six continents. The cohort encompassed lifestyles ranging from hunter-gatherer, pastoralist, and farming communities to industrialized economies. The authors evaluated the relative contributions of body size-adjusted energy expenditure, estimated caloric intake, and dietary ultraprocessed food content (available for 25 populations) to obesity metrics across the economic spectrum.
What was found
Economic development was positively associated with higher body mass, BMI, body fat, and absolute total, basal, and activity energy expenditure. When adjusted for body size, total and basal energy expenditures decreased by approximately 6% to 11% with increasing economic development, but displayed high population variability and did not track closely with lifestyle categories. Size-adjusted total energy expenditure accounted for only roughly one-tenth (~10%) of the higher body fat percentage and BMI linked to economic development. Estimated energy intake was higher in developed populations, and in 25 populations with dietary data, the proportion of ultraprocessed foods correlated positively with body fat percentage.
Why it matters
These findings challenge the common assumption that declining energy expenditure from sedentary lifestyles is the primary cause of rising obesity in developing and developed economies. Instead, the data indicate that increased caloric consumption and dietary composition (specifically ultraprocessed foods) drive the vast majority of global obesity increases.
Limits
The study is cross-sectional, preventing causal inference. Dietary ultraprocessed food data were available for only 25 of the 34 populations, and energy intake was estimated rather than directly observed over time. Unmeasured confounders across diverse geographical and cultural groups may also influence body composition.
Cited by
- supports An analysis of 34 countries led by Duke researchers showed that 90% of the obesity epidemic can be explained by diet alone rather than lack of physical activity.