Comparison of fat-free mass in super obesity (BMI ≥50 kg/m2) and morbid obesity (BMI <50 kg/m2) in response to different weight loss surgeries

Background: Differences in excess weight loss, body mass index (BMI) change, and body composition have been related to different types of bariatric procedures. Our objective was to explore these alterations related to body mass in superobese (SO) and morbidly obese (MO) patients in a university hospital setting. Methods: Patients provided written informed consent and had their body composition measured before and after surgery using bioimpedance (Tanita 310). The t test was used to compare MO and SO. Pearson's correlations were used to examine the BMI, excessive BMI loss, percentage of body fat (BF) change, and fat-free mass. Results: A total of 133 MO patients had a BMI of 43.3 kg/m(2) and 88 SO patients had a BMI of 59.4 kg/m(2). The percentage of BF was 46.7% and 51.9% (P < .0001). The differences in the follow-up period after surgery (21.5 and 20.6 months; P = .62) and patient age (43.4 and 42.5 yr) were not significant, but the gender distribution was significant (P = .003). After surgery, the MO patients had a BMI of 30.9 +/- 5.7 kg/m(2) and the SO patients had a BMI of 37.3 +/- 9.0 kg/m(2). The percentage of BF was not different between the 2 groups (MO, 33.1% +/- 9.6% and SO, 35.0% +/- 12.4%; P = .21). Gender differences in the percentage of BF were present before surgery; however, after surgery, these were absent for the men in the 2 groups (24.8% and 26.6%; P = .51). The change in the BMI and the change in the BF had a stronger correlation for the MO patients (r = .83 versus r = .53) than for the SO patients. The fat-free mass loss correlated with the change in BMI without regard to procedure. The percentage of excessive BMI loss was 65.1% for the MO and 63.4% for the SO patients (P = .64). Conclusions: The SC) patients achieved excessive BMI loss similar to that of the MO patients, with more SO men choosing biliopancreatic diversion/duodenal switch. At a BMI of 37.3 kg/m(2), the SO patients had a percentage of BF that was not different from that of the MO patients at 30.9 kg/m(2). The fat-free mass losses correlated with the change in BMI. (Surg Obes Relat Dis 2012;8:255-259.) (C) 2012 American Society for Metabolic and Bariatric Surgery. All rights reserved.