Characteristics of the study group
The age of the study participants ranged from 18 to 76 years old (mean age 44.0 ± 13.5). The mean body weight and height in the study group was 87.8 ± 22.6 kg and 165.9 ± 6.9 cm, equally. BMI results were interpreted on the basis of the classification of index values suggested by WHO [35]: <18.5 kg/m2 - underweight; 18.5-24.9 kg/m2 - normal weight; 25.0-29.9 kg/m2 - overweight; 30.0 -34.9 kg/m2 – obesity class I; 35.0-39.9 kg/m2- obesity class II; >40.0kg/m2- obesity class III. The mean value of BMI among the participants was 32.0 ± 8.7 kg/m2. The 26.9% percentage of participants (n = 29) were of normal weight, 25.0% (n = 27) had obesity class I. An equal number of patients (17.6%; n = 19) were overweight or had obesity class III (17.6%; n = 19), and the lowest percentage of patients had obesity class II (13.0%; n = 14). The mean waist circumference in the study group was 96.1 ± 17.7 cm. The percentage of individuals whose waist circumference was greater than 80 cm but smaller than 88 cm was 13.9% (n = 15), while individuals whose waist circumference was greater than 88 cm represented the largest percentage of the subjects (64.8%; n = 70). Only 21.3% of the subjects (n = 23) had normal waist circumference. The mean value of WHR in the study group was 0.83 ± 0.1. The WHR value was equal to or greater than 0.85 in 38.9% of all study participants (n = 42).
Actual and predicted resting metabolic rate (RMR)
The mean aRMR was 1705.2 ± 320.7 kcal/day. The mean pRMR ranged from 1281.1 ± 104.7 kcal/day (measured by BIA) to 1906.3 ± 276.3 kcal/day (estimated by Müller et al. predictive equation). Pearson correlation analysis showed that all predictive equations estimating RMR significantly correlated with aRMR. All correlation coefficients between RMR measured with predictive equations and aRMR were very high except for the correlation between aRMR and RMR calculated with BIA, which was statistically insignificant and weak.
The detailed results of characterization and the results of correlation between aRMR and pRMR are described are presented in Table 2.
Table 2
The characteristics of RMR estimated with different methods (n=108)
Method
|
RMR [kcal/day]
|
Pearson correlation coefficient
|
Mean ± SD
|
Median
|
Min
|
Max
|
aRMR (kcal/kg/day)
|
20.0 ± 3.7
|
19.7
|
10.2
|
30.1
|
-
|
aRMR (kcal/day)
|
1705.2 ± 320.7
|
1687.5
|
1032.0
|
2775.0
|
-
|
Harris-Benedict [22]
|
1596.0 ± 202.2
|
1565.1
|
1275.2
|
2204.7
|
0.753*
|
Mifflin et al. [23]
|
1528.5 ± 220.2
|
1495.2
|
1131.8
|
2132.3
|
0.734*
|
Bernstein et al. [24]
|
1299.2 ± 156.9
|
1269.4
|
1064.8
|
1794.3
|
0.759*
|
Owen et al. [25]
|
1425.5 ± 162.4
|
1406.0
|
1155.4
|
1920.8
|
0.739*
|
FAO/WHO [26]
|
1584.1 ± 199.5
|
1562.7
|
1223.7
|
2189.5
|
0.748*
|
Cunningham [27]
|
1574.4 ± 465.5
|
1468.5
|
908.6
|
3421.8
|
0.754*
|
Müller et al. [28]
|
1906.3 ± 276.3
|
1867.7
|
1414.4
|
2709.0
|
0.703*
|
Korth et al. [29]
|
1641.4 ± 224.1
|
1612.9
|
1219.4
|
2225.2
|
0.723*
|
Lazzer et al. [30]
|
1676.5 ± 237.2
|
1648.0
|
1213.2
|
2304.8
|
0.730*
|
Huang et al. [31]
|
1532.3 ± 220.3
|
1499.9
|
1162.1
|
2172.5
|
0.750*
|
Henry’s [32]
|
1542.5 ± 214.8
|
1510.7
|
1211.9
|
2218.3
|
0.763*
|
IOM [33]
|
1551.5 ± 188.7
|
1518.5
|
1241.0
|
2093.9
|
0.749*
|
aRMR - actual resting metabolic rate; FAO - Food Agriculture Organization; WHO - the World Health Organization; IOM - the Institute of Medicine; BIA - bioelectrical impedance analysis; *p < 0.001.
We reported the smallest mean difference between pRMR and aRMR for Lazzer et al. equation (28.6 ± 219.3 kcal / day; p = 0.178), and the highest mean difference for BIA (424.0 ± 326.6 kcal / day; p <0.001). Most of predictive equations and BIA significantly underpredicted aRMR, except for the Müller et al. equation [28], which significantly overpredicted RMR. The most overpredicted RMR was obtained with Bernstein et al. [24] and Owen et al. equations [25] (Table 3).
Table 3
Differences between aRMR and pRMR (n=108)
Method
|
ΔRMR kcal/day
|
SD
|
ΔRMR kcal/day
% aRMR
|
Harris-Benedict [22]
|
109.1*
|
214.7
|
6.4
|
Mifflin et al. [23]
|
176.7*
|
218.3
|
10.4
|
Bernstein et al. [24]
|
406.0*
|
226.0
|
2.8
|
Owen et al. [25]
|
279.7*
|
228.7
|
16.4
|
FAO/WHO [26]
|
121.1*
|
216.6
|
7.1
|
Cunningham [27]
|
130.8*
|
307.5
|
7.7
|
Müller et al. [28]
|
-201.1*
|
233.8
|
-11.8
|
Korth et al. [29]
|
63.7*
|
221.7
|
3.7
|
Lazzer et al. [30]
|
28.6
|
219.3
|
1.7
|
Huang et al. [31]
|
172.9*
|
213.0
|
10.1
|
Henry’s [32]
|
162.7*
|
209.4
|
9.5
|
IOM [33]
|
153.6*
|
218.7
|
9.0
|
BIA
|
424.0*
|
326.6
|
24.9
|
FAO – the Food Agriculture Organization; WHO – the World Health Organization; IOM - the Institute of Medicine; BIA- bioelectrical impedance analysis; ΔRMR – mean difference between aRMR and pRMR; *p<0.01; p<0.05 - statistically significant values; df = 107.
Korth et al. predictive equation was the most accurate in comparison to aRMR due to its lowest individual variability. Values of Korth et al. [29], Harris-Benedict [22] and Lazzer et al. [30] equations were within 10% of the measured aRMR in more than 50% of the study participants: (Figure 1).
Based on the Blind-Altman analysis results, we observed a significant dispersion of individual scores for most equations, which means that they were weakly correlated with aRMR. The only exception was for the Müller et al. equation [28], which significantly overestimated the value of aRMR, but to a similar extent in the entire set of predictive equations, regardless of the individual aRMR results (Figure 2). The Pearson’s coefficients r for correlation between the averaged pRMR and aRMR values, and the difference between them are presented.
Anthropometric measurements vs aRMR and pRMR
The mean percentage of BF mass among our study participants was 37.5 ± 7.4%. BF was higher than or equal to 30.0% in 88 patients (81.5%). Most study participants (47.2%; n = 51) were morbidly obese, with BF higher than 40.0%. VFL ranged from 3 to 20 (mean 13.4 ± 5.1). Over 70.0% (71.3%; n = 77) of study participants had a high VFL, including 43.5% with very high VFL. Characteristics of anthropometric measurements is shown in Table 4.
Table 4
Characteristics of anthropometric measurements (n=108)
Measurement
|
Mean ± SD
|
Median
|
Min
|
Max
|
Lean body mass - LBM [%]
|
53.4 ± 9.0
|
51.9
|
37.0
|
84.7
|
Lean body mass - LBM [kg]
|
48.8 ± 21.2
|
44.0
|
18.6
|
132.8
|
Soft lean mass - SLM [kg]
|
48.5 ± 7.8
|
46.8
|
34.1
|
76.0
|
Soft muscle mass - SMM [kg]
|
29.1 ± 4.7
|
28.0
|
20.4
|
45.6
|
Total body water - TBW [%]
|
38.5 ± 6.5
|
37.3
|
26.6
|
61.0
|
Mass body fat - MBF [kg]
|
34.4 ± 14.3
|
33.6
|
11.6
|
72.1
|
Percentage body fat - PBF [%]
|
37.5 ±7.4
|
39.0
|
15.9
|
48.7
|
Visceral fat level - VFL
|
13.4 ± 5.1
|
14.0
|
3
|
20
|
Body Mass Index - BMI [kg/m2]
|
32.0 ± 8.7
|
31.6
|
18.8
|
62.4
|
All anthropometric measurements positively correlated with aRMR and pRMR. We reported a moderate correlation between VFL and aRMR; a strong correlation between BMI and aRMR; and almost full correlation between BMI and the pRMR. Table 5 presents detailed results of Pearson correlation analysis between anthropometric measurements and pRMR/aRMR.
Table 5
Results of Pearson correlation analysis between anthropometric measurements and pRMR/aRMR (n=108)
Method
|
Anthropometric measurements and BMI
|
LBM [%]
|
LBM [kg]
|
SLM [kg]
|
SMM [kg]
|
TBW [%]
|
MBF [kg]
|
PBF [%]
|
VFL
|
BMI [kg/m2]
|
LBM [%]
|
Harris-Benedict [22]
|
.9613*
|
.9561*
|
.9560*
|
.9564*
|
.9612*
|
.8948*
|
.6948**
|
.6250**
|
.8373*
|
.9613*
|
Mifflin et al. [23]
|
.9569*
|
.9292*
|
.9557*
|
.9560*
|
.9568*
|
.8447*
|
.6295**
|
.5603**
|
.7680*
|
.9569*
|
Bernstein et al. [24]
|
.9613*
|
.9747*
|
.9522*
|
.9526*
|
.9612*
|
.9369*
|
.7553*
|
.6885**
|
.8946*
|
.9613*
|
Owen et al. [25]
|
.9552*
|
.9851*
|
.9417*
|
.9420*
|
.9551*
|
.9824*
|
.8362*
|
.7832*
|
.9515*
|
.9552*
|
FAO/WHO [26]
|
.9591*
|
.9699*
|
.9498*
|
.9500*
|
.9590*
|
.9403*
|
.7716*
|
.7055**
|
.8982*
|
.9591*
|
Cunningham [27]
|
.9776*
|
1.0000**
|
.9694*
|
.9696*
|
.9777*
|
.9447*
|
.7419*
|
.6816**
|
.9263*
|
.9776*
|
Müller et al. [28]
|
.9204*
|
.9624*
|
.9040*
|
.9043*
|
.9203*
|
.9851*
|
.8685*
|
.8262*
|
.9645*
|
.9204*
|
Korth et al. [29]
|
.9535*
|
.9165*
|
.9540*
|
.9542*
|
.9534*
|
.8242*
|
.6051**
|
.5373**
|
.7395*
|
.9535*
|
Lazzer et al. [30]
|
.9804*
|
.9666*
|
.9748*
|
.9750*
|
.9803*
|
.9164*
|
.7332*
|
.6782**
|
.8466*
|
.9804*
|
Huang et al. [31]
|
.9791*
|
.9758*
|
.9724*
|
.9727*
|
.9790*
|
.9272*
|
.7398*
|
.6778**
|
.8682*
|
.9791*
|
Henry’s [32]
|
.9604*
|
.9767*
|
.9506*
|
.9509*
|
.9602*
|
.9454*
|
.7717*
|
.7049**
|
.9066*
|
.9604*
|
IOM [33]
|
.9766*
|
.9667*
|
.9714*
|
.9717*
|
.9765*
|
.9080*
|
.7123**
|
.6480**
|
.8441*
|
.9766*
|
RMR
|
.7340*
|
.7536*
|
.7273*
|
.7278*
|
.7328*
|
.7077**
|
.5421**
|
.4763**
|
.6854**
|
.7340*
|
FAO - Food Agriculture Organization; WHO - the World Health Organization; IOM - the Institute of Medicine; BIA - bioelectrical impedance analysis. p<0.05 - statistically significant values, *p < 0.01; **p < 0.001; p<0.05 - statistically significant values.
To further evaluate the correlation between anthropometric measurements and aRMR, we performed PCA. It enabled to define the two principal components, PC1 and PC2, which represent the sets of strongly intercorrelated variables (Table 6). They can be interpreted as fat free mass components and fat mass components with BMI, respectively. PC1 and PC2 groups significantly correlated with aRMR (r = 0.66 and r = 0.34, respectively; p < 0.001). However, PC1 group (fat-free mass components) more significantly correlated with aRMR than PC2 group (fat mass components with BMI). Figure 3 presents the relationship between aRMR and PC1 (fat-free mass components) and PC2 (fat mass components with BMI).
Table 6
Results of PCA of the anthropometric measurements (n=108)
Anthropometric measurements
|
PC1
Fat-free mass components
|
PC2
Fat mass components and BMI
|
LBM [%]
|
0.93
|
0.36
|
LBM [kg]
|
0.87
|
0.49
|
SLM [kg]
|
0.94
|
0.33
|
SMM [kg]
|
0.94
|
0.33
|
TBW [%]
|
0.93
|
0.36
|
MBF [kg]
|
0.67
|
0.74
|
PBF [%]
|
0.34
|
0.93
|
VFL
|
0.26
|
0.95
|
BMI [kg/m2]
|
0.64
|
0.72
|
Part [%]
|
0.589
|
0.395
|
LBM - lean body mass; SLM - soft tissue mass; SMM - muscle tissue mass; TBW - total body water; MBF - mass body fat; PBF - percentage body fat; VFL - visceral fat level; BMI - body mass index