Ecological studyindependent cross-checkabstract checked★ key study I-LIFE-105 standard review

Less active jobs and weight gain

Trends over 5 decades in U.S. occupation-related physical activity and their associations with obesity.

Overview

Church TS et al.. PLoS One 2011 · PMID 21647427 · DOI 10.1371/journal.pone.0019657

US jobs became less active since 1960, and models suggest this could explain much of the weight gain.

Does the study support the specific claim? Partly · Methodological quality: low

Study explained simply

What did the researchers want to find out?: Link job activity to weight trends.
How was the study done?: Modelling with labour and survey data.
How many people, animals or samples were studied?: US population.
What was actually found?: >100 kcal/day decrease in job energy expenditure.
How large was the observed effect?: 142 kcal/day in men.
What do the results mean in everyday life?: Less physical work may contribute to weight gain.
What are the study's limitations?: Ecological model.
What does it say about Elawady's specific claim?: Partly supports the claim.
Do the results apply to Germany and Europe?: Applies; same physiology.
What can explicitly not be concluded from this study?: Individual causation.

Authors: Church TS et al.
Journal: PLoS One
Year: 2011
Identifier: PMID 21647427 DOI 10.1371/journal.pone.0019657
Verification: verified – PubMed efetch 2026-10-26; Crossref update-to/updated-by check
Retracted: no
Corrections: none
Extent checked: abstract only
Conflicts of interest and funding: not stated in abstract

How have occupational physical activity trends related to US weight gain since 1960?

Study design: Ecological study – Ecological modelling study (labour statistics + NHANES weights)
Population: US workforce
Country: USA
Period: 1960-2006
Sample size: Population data (US Bureau of Labor Statistics; NHANES)
Inclusion and exclusion criteria: not stated in abstract

Results: Jobs requiring at least moderate activity fell from almost half to <20%; daily occupation-related energy expenditure fell by >100 kcal; in men a 142 kcal decrease predicted weight rising from 76.9 kg to 89.7 kg, close to observed 91.8 kg.
Absolute risks: not reported
Authors' conclusion: Reduced occupational energy expenditure accounts for a significant portion of the increase in mean US body weights.

Model fit does not prove causation; contradicted by direct DLW data (I-LIFE-104).

Strongest supporting evidence for inactivity as a major cause of weight gain; weak design.

Universal biology; applies in Europe and Egypt.

Supporting but low quality; outweighed by direct energy expenditure measurements.

Multidimensional assessment
Multidimensional assessment
Authenticity of the source	verified
Methodological quality	low
Risk of bias	high
Precision of results	not applicable
Directness	indirect
Reproducibility	not replicated
Consistency with the overall evidence	inconsistent
Regional transferability	moderate
Adequacy of the interpretation (by the archive)	not applicable