Introduction: The body mass index (BMI) is the most practical method to measure and compare obesity between individuals. The Percentage of Excess BMI Loss (PEBMIL) is used to present results in operated patients and is based on the premise that a BMI-25 is the final aim, on being the upper limit in normal subjects. It is possible to achieve a BMI-25 in morbid obese (MO) patients with initial low BMIs (<50) but it is rare in overweight (OW) patients with a BMI>50. Expected BMI (EBMI) would be that which should be reached by all subjects depending on their initial BMI.
Objective: The objective of this study is to search for, using statistical methods, a formula based on clinical evidence that can identify the EBMI depending on the initial BMI.
Patients and method: We analysed the initial and final BMI in a group of 135 MO patients, operated on using the duodenal switch procedure and with a follow up of over 3 years. A linear regression method has been used to obtain a formula that could calculate the EBMI of each patient operated on.
Results: We obtained an algorithm in which EBMI=Initial BMIx0.33+14. If we apply the individualised EBMI instead of the BMI-25, the median PEBMIL was 99.48 (range: 76.75-110.46).
Conclusion: This result suggests that the application of an individual EBMI is a more reliable estimate of the success or failure of bariatric operations.