Does Aging Affect Diet-Induced Thermogenesis? Revisiting the Evidence from Human Studies.
Level 5 - mechanism / opinion, no new human data
Narrative review of comparative human studies
PubMed 42371245 · doi:10.1007/s13679-026-00730-7
What was done
The authors conducted a narrative review of 14 human studies comparing diet-induced thermogenesis (DIT) between younger and older adults, evaluating methodological factors (such as postprandial measurement duration) and physiological factors (such as fat-free mass, sympathetic nervous system activity, gastric emptying, and meal macronutrient composition) across the literature.
What was found
Of the 14 included studies, 6 reported significantly lower DIT in older adults and 8 reported no significant age-related differences. Studies reporting lower DIT in older adults measured postprandial energy expenditure over shorter durations (≤ 240 min), whereas studies with longer measurement protocols found no differences. Lower fat-free mass in older cohorts did not consistently explain discrepancies, and mechanistic factors (sympathetic activity, gastric emptying, meal composition) showed no consistent mediating effects.
Why it matters
Age-related declines in energy expenditure are often assumed to include decreased diet-induced thermogenesis. This synthesis indicates that observed age differences may be artifacts of short postprandial measurement durations rather than true biological impairments in thermogenic capacity.
Limits
The paper is a narrative review without pooled meta-analytic effect sizes or systematic search criteria detailed in the abstract. Total participant sample size is not reported in the abstract. Differences in body composition matching, meal composition, and protocol durations across primary studies leave the independent effect of aging on DIT unresolved.