A new resting metabolic rate equation for women with class III obesity.

OBJECTIVE

Resting metabolic rate (RMR) is an important parameter to guide the nutritional therapy of class III obese patients. The aims of the present study were to develop a predictive equation for RMR estimation in class III obese women using anthropometric indicators and to compare indirect calorimetry with other predictive equations.

METHODS

This was a cross-sectional study on women with class III obesity (body mass index >40 kg/m2). Weight, height, fat-free mass, fat mass, and RMR of all individuals were measured. Multiple linear regression was used to determine the new RMR equation and the Bland-Altman plot was used to analyze the agreement between indirect calorimetry and the results of predictive equations.

RESULTS

We evaluated 101 women with obesity class III and a mean age of 36.3 ± 10 y. The anthropometric and body composition variables used in the new equation had a coefficient of determination of 0.80, and a significant influence on RMR (P = 0.01). Harris-Benedict and World Health Organization equations showed similar bias and limits (181.6, +2 SD = 765.5, -2 SD = -402.2; 156.4, +2 SD = 799.4, -2 SD = -486.6, respectively). The Mifflin-St Jeor and Owen equations showed large clinical bias (mean, 239.2 and 463.9, respectively), and a tendency to overestimate RMR.

CONCLUSION

The prediction equations tested in the study had low accuracy in estimating RMR of women with class III obesity. However, our equation was developed specifically for this population, using variables known to influence their energy expenditure.