Abstract: The multiplicity of resting metabolic rate (RMR) prediction equations indicates that many variables affect RMR, making it difficult to adopt a single equation for all individuals who wish to lose, gain or maintain weight. PURPOSE: To improve the accuracy of RMR prediction equations for obese individuals and to construct a new formula to evaluate RMR after weight loss (WL). METHODS: This study examined the RMR gap in 21 men (M) and 18 women (W), 25-60 yrs, with 27< BMI< 40 kg/m2 and 10-20% WL after at least three months in a structured weight reduction program with a customized diet and professionally tailored exercise prescription. At entry and at follow-up visits participants’ RMR, weight, height, fat-free mass (FFM), fat mass (FM),were measured with reliable instruments to ascertain the RMR change relative to FFM and FM. Pre and post RMR measurements were compared to calculated RMR using existing Harris and Benedict (HB), Ravussin and Bogradus (RB) and Johannsen et al. (J). T-test, ANOVA and χ2 test comparisons were analyzed using SPSS 19.0, significance level P>0.05. To improve accuracy new prediction equations were constructed through stepwise linear regression based on before (RMRb) and after (RMRa) RMR measurements: M: RMRb=132.82+28.37(W)-250.595(H)+9.464(FFM)-2.871(A)-25.932(FM) M: RMRa=1862.68-7.779(W)+1716.697(H)+18.091(FFM)+1.964(A)+14.972(FM) W: RMRb=553.971+16.601(W)+1033.839(H)-13.734(FFM)-10.930(A)-19.668(FM) W: RMRa=552.850+7.288(W)+340.730(H)+8.932(FFM)-5.064(A)-5.015(FM). RESULTS: In M and W there was a significant difference in WL (M: 104±13 vs. 87±11; W: 88±10 vs.75±8, P≤0.01), BMI (M: 33±3 vs. 28±3; W: 32±4 vs. 27±3, P≤0.01) and FM in kg (M: 37±7 vs. 26±9; W: 40±9 vs.27±8, P≤0.01); M only in FFM (65±9 vs.63±9, P=0.02 );W only in RMR (1802±176 vs.1684±176, P=0.04). Calculated RMR before and after WL using the J equation was closest to measured RMR in M and W before and in W after WL (M: -337±223; W: -57±256, vs. -69±128); but only accurate was W before WL (P=0.351). RMR calculations with the new equations were more accurate and closest to measured RMR before and after WL in M(-0.05±154 vs. 0.03±197) but only after WL in W (-30±116). CONCLUSION: The study illuminates the need to adopt different equations for assessment of individuals’ RMR before and after weight loss.
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