Key result
Novel metabolic coefficient K_FFM neutralizes adiposity bias and detects metabolic shifts over traditional REE/FFM.
Why the study?
In patients with obesity, conventional resting energy expenditure normalization using the resting energy expenditure to fat-free mass ratio is confounded by the metabolic contribution of adipose tissue, introducing an anthropometric bias across varying adiposity levels.
Does a new corrected metabolic coefficient (KFFM) neutralize anthropometric bias and show longitudinal responsiveness in obese patients undergoing an 8-week rehabilitation program?
Observational (n=167)
Does a new corrected metabolic coefficient (KFFM) neutralize anthropometric bias and show longitudinal responsiveness in obese patients undergoing an 8-week rehabilitation program?
KFFM provides a bias-reduced, robust metric for resting energy expenditure normalization in obesity, outperforming traditional ratio-based methods.
Background and Aims 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. Method and Results 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 (5,000 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) Conclusions 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.
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Mazzola et al. (2026) conducted an observational in Class I-III obesity (n=167). Corrected metabolic coefficient (K FFM) vs. Traditional REE/FFM ratio was evaluated on Bias neutralization (correlation with adiposity). The corrected metabolic coefficient (K FFM) neutralized adiposity bias (r=0.098, p=0.21) unlike the traditional REE/FFM ratio (r=0.25, p=0.001), and detected significant metabolic shifts.
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