Sum of Skinfold-Corrected Girths Correlates with Resting Energy Expenditure: Development of the NRGCO Equation

Our study aimed to validate existing equations and develop the new NRG_CO equation to estimate resting energy expenditure (REE) in the Colombian population with moderate-to-high physical activity levels. Upon satisfying the inclusion criteria, a total of 86 (43F, 43M) healthy adults (mean [SD]: 27.5 [7.7] years; 67.0 [13.8] kg) were evaluated for anthropometric variables and REE by indirect calorimetry using wearable gas analyzers (COSMED K4 and K5). Significant positive correlations with REE were found for body mass (<i>r</i> = 0.65), body mass-to-waist (<i>r</i> = 0.58), arm flexed and tensed girth (<i>r</i> = 0.66), corrected thigh girth (<i>r</i> = 0.56), corrected calf girth (<i>r</i> = 0.61), and sum of breadths (∑3D, <i>r</i> = 0.59). As a novelty, this is the first time a significant correlation between REE and the sum of corrected girths (∑3CG, <i>r</i> = 0.63) is reported. Although existing equations such as Harris-Benedict (<i>r</i> = 0.63), Mifflin-St. Jeor (<i>r</i> = 0.67), and WHO (<i>r</i> = 0.64) showed moderate-to-high correlations with REE, the Bland-Altman analysis revealed significant bias (<i>p</i> < 0.05), indicating that these equations may not be valid for the Colombian population. Thus, participants were randomly distributed into either the equation development group (EDG, <i>n</i> = 71) or the validation group (VG, <i>n</i> = 15). A new model was created using body mass, sum of skinfolds (∑8S), corrected thigh, corrected calf, and age as predictors (<i>r</i> = 0.755, R² = 0.570, RMSE = 268.41 kcal). The new NRG_CO equation to estimate REE (kcal) is: 386.256 + (24.309 × BM) - (2.402 × ∑8S) - (21.346 × Corrected Thigh) + (38.629 × Corrected Calf) - (7.417 × Age). Additionally, a simpler model was identified through Bayesian analysis, including only body mass and ∑8S (<i>r</i> = 0.724, R² = 0.525, RMSE = 282.16 kcal). Although external validation is needed, our validation resulted in a moderate correlation and concordance (bias = 91.5 kcal) between measured and estimated REE values using the new NRG_CO equation.