Longitudinal validation of an original bias-reduced fat-free mass metabolic coefficient in inpatients with obesity.

Authors

Giuseppe Mazzola, Simone Perna, Clelia Russo, Valentina Nerbi, Veronica Piccinni, Sara Carovelli, Carlo Cattaneo, Michela Seniga, Luca Matteo Schiavi, Eleonora Patta, Mariangela Rondanelli

Published in

Nutrition, metabolism, and cardiovascular diseases : NMCD. Pages 105000. Sep 12, 2026. Epub Sep 12, 2026.

Abstract

In obese patients subjects, conventional resting energy expenditure (REE) normalization using the REE/fat-free mass (FFM) ratio is confounded by the metabolic contribution of adipose tissue, introducing an anthropometric bias across varying levels of adiposity. This study validates a new corrected metabolic coefficient (K_FFM) designed to neutralize this bias and evaluates its longitudinal responsiveness and clinical reliability during a 8-week multidisciplinary rehabilitation intervention.
Longitudinal study of 167 patients subjects with Class I-III obesity undergoing an 8-week residential program. REE and body composition were assessed by indirect calorimetry and DXA. KFFM was calculated by adjusting REE for fat mass. Bias was evaluated by Pearson correlation; longitudinal changes by Linear Mixed Models; metabolic convergence by Brown-Forsythe test and bootstrapping (5000 iterations). MDC was set at 2.30 kJ/kg/day. Allometric modeling confirmed a non-linear REE-FFM relationship with an exponent of β = 0.82 (p = 0.0007). The K_FFM achieved complete bias neutralization (r = 0.098,p = 0.21), whereas the traditional REE/FFM ratio remained significantly correlated with adiposity (r = 0.25,p = 0.001). Longitudinal analysis revealed a significant overall metabolic shift (p = 0.0009), with a highly significant reduction in K_FFM specifically for Class III obesity (from 118.11 to 109.95 kJ/kg FFM/day; p = 0.0004). Furthermore, 91.02% of patients subjects exhibited changes exceeding the minimum detectable change (MDC = 2.30 kJ/kg/day), confirming true physiological signals. Bootstrap analysis confirmed the stability of inter-individual variance (95% CI: -14.74 to 7.08).
K_FFM could be a bias-reduced, robust metric for REE normalization in obesity, showing stable inter-individual variability and sensitivity to clinically meaningful bioenergetic changes beyond traditional ratio-based methods.

PMID:
42760236
Bibliographic data and abstract were imported from PubMed on 19 Sep 2026.

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