Measurement of Fecal Energy Loss Using Bomb Calorimetry in Adult Patient Populations: A Systematic Review and Meta-Analysis.

Background/Objectives: Accurate assessment of nutritional adequacy requires insight not only into energy intake but also into the proportion of nutrients absorbed. Stool bomb calorimetry quantifies fecal energy content and estimates intestinal energy absorption, but its application and reporting vary. We aimed to evaluate its application in adult patient populations and to quantify intestinal energy absorption and its variability. Methods: PubMed, Embase, ClinicalTrials.gov, BASE and NDLTD were searched without date restriction (PROSPERO CRD420261389214). Two reviewers screened independently, and risk of bias was assessed using design-appropriate JBI checklists. Studies reporting percentage absorption with recoverable variance were pooled using a random-effects model; a post hoc subgroup analysis by patient population was performed. Results: Twenty-eight studies (1981-2026) were included; seventeen contributed to the meta-analysis (439 participants). Absorption ranged from 50.0% to 91.9%. The pooled estimate was 74.2% (95% CI 67.9-80.5), with substantial heterogeneity (I2 = 96.3%) and a 95% prediction interval of 48.8-99.6%. Patient population explained most of the between-study variance (pseudo-R2 = 82%): 62.9% (95% CI 57.4-68.5) in short bowel syndrome and intestinal failure versus 85.1% (95% CI 81.2-88.9) in other populations (p < 0.001). Calibration and replicate determinations were each reported in one of 28 studies. Conclusions: Intestinal energy absorption varies widely across adult patients, but the variation is largely structured by population. Patients with short bowel syndrome or intestinal failure absorb approximately 63% of ingested energy, more than 20 percentage points less than other adult populations. Prescribed energy intake should not be assumed to equal absorbed energy. Standardized reporting of measurement procedures is needed before clinical use can be evaluated.