Can RMR be accurately measured in the obese population & is it a predictor of postop weight loss in patients undergoing laparoscopic VSG?

Andrew R Brownlee, MD, Erica N Bromberg, BA, Deodate Davis, BA, Mitchel Roslin, MD, FACS. Lenox Hill Hospital

Introduction

Weight loss and gain are due to an imbalance of energy consumption and utilization. The impact of RMR on weight loss following VSG is unknown. As a result we wanted to answer whether a morbidly obese cohort has higher or lower RMR, if VSG increases resting energy expenditure thus reducing the predicted reduction in RMR with weight loss and if those with a faster preoperative metabolic rate will loose more weight postoperatively.

Methods

Fifty patients who underwent a VSG had their RMR measured preoperatively and at intervals of 1,3 and 6 months post-op using an indirect calorimeter. Hey were made NPO for five hours prior the study. Predicted RMRs were determined using the Harris-Benedict equation.

Results

There were 37 females and 13 males with a mean preoperative BMI of 42.8 . The ratio of actual to predicted RMR preoperatively was 0.96. There was no statistically significant difference in the actual and predicted RMR at any time point. The quartile of patients with the highest RMR was on average 19% above predicted. These patients lost 18% of their total body weight(TBW) at the longest point of follow-up while the patients with the lowest quartile RMR were, on average 27% below predicted and lost 20% of their TBW.

Conclusion

Measured RMR is not significantly different than predicted in this cohort. Decline in RMR following VSG occurs as would be predicted, indicating that VSG does not increase resting energy expenditure. Individuals with higher than predicted metabolic rates do not loose more weight post-VSG suggesting that other post-operative factors are responsible for weight loss rather than intrinsic metabolic rate.

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