Body composition change after bariatric surgery

Narong Boonyagard, MD, Pondech Vichajarn, Rapheephat Tanomphetsanga, Jakrapan Wittayapairoch, Krit Kitisin, Suppa-ut Pungpapong, Chadin Tharavej, Patpong Navicharern, Suthep Udomsawaengsup. Chulalongkorn Hospital


Bariatric surgery is one of treatment choices for morbid obesity patients because of its effective weight loss. To improve positive effects on metabolic risks, this weight loss should be primary from body fat mass (BFM). The aim of this study is to analyze the body composition for determining FFM, BFM, and basal metabolic rate (BMR) before and after bariatric surgery


Patients performed bariatric surgery in King Chulalongkorn Memorial Hospital University between September 2014 and March 2015 were prospectively collected. Patients’ weights and body compositions were recorded by using bioelectrical impedance analysis (BIA). Weight, BFM, FFM, and BMR were measured before and 1, 3 and 6 months after bariatric surgery. The changes in body composition were analyzed


A total of 18 patients were included with at least 6 months follow up, 13 for LRYGB and 5 for LSG. There were 8 females and 10 males with an average age of 36.33 years old. The average BMI before surgery was 52.02 kg/m2 and 6 months after surgery was 37.84 kg/m2. The average %EWL was 53.37%. The average of BFM before surgery and 6 month after surgery were 76.24±22.86 and 46.16±17.21 kg (P<.001) respectively. The average of FFM before surgery and 6 month after surgery were 74.86±19.08 and 63.32±15.00 kg (P<.001) respectively.

In 6 months after surgery, patient had lost 41.62 of body weight (30.08 kg of BFM and 11.54 kg of FFM). We mainly found a decrease in BFM (39.49±12.58%) whereas FFM was slightly reduced (14.76±6.87%). 

The significant decrease in BMR (1933.73±401.03 vs 1772.83±356.71 Kcal P<.001) was observed only from before surgery to 1 month after surgery. Thereafter, there was no significant change in BMR at 3 and 6 months (1765.73 ±374.78, 1737.23 ±324.05). Between these two operations, LRYGB seems to preserve overall FFM comparable to LSG.


The weight loss after bariatric surgery is mainly due to a reduction in BFM with less impact on the FFM (39.49% vs 14.76%). BMR

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