The evidence for constrained total energy expenditure in humans and other animals.
Level 5 - mechanism / opinion, no new human data
Narrative review and quantitative modeling framework synthesizing published human and animal data without a formal systematic review protocol
PubMed 41653928 · doi:10.1016/j.cub.2026.01.025
What was done
The authors developed quantitative frameworks to model additive versus constrained total energy expenditure (TEE) and compared model predictions against data synthesized from experimental physical activity interventions and ecological studies in free-living human and animal populations.
What was found
In human aerobic exercise interventions, total daily energy expenditure increased by only ~30% of the amount predicted by additive models. Compensation appeared reduced with resistance training and amplified when aerobic exercise was paired with dietary restriction. In animal experiments, which often involve dietary restriction, compensation was generally ~100%. Reductions in basal metabolic rate and sleeping metabolic rate contributed to compensation (notably in animal studies and longer-duration human studies) but did not fully account for the total daily energy expenditure compensation observed.
Why it matters
This paper challenges traditional additive models of energy balance in humans and animals, demonstrating that energy expenditure is constrained through compensation in non-exercise metabolic components.
Limits
The abstract describes a synthesis and quantitative modeling without reporting systematic review methodology, exact search criteria, or total sample size (n). The precise non-basal physiological mechanisms mediating energy compensation remain incompletely identified.