Background: This study aimed to evaluate changes in body tissue composition with obesity surgery regarding visceral fat, subcutaneous fat, and skeletal muscle.
Design: Prospective non-randomized single-center cohort study METHODS: Whole-body magnetic resonance imaging (MRI) measured volumes of subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), and skeletal muscle (SM) in 31 patients with laparoscopic sleeve gastrectomy (LSG, 20) or Roux-en-Y gastric bypass (RYGB, 11) preoperatively, at three- and 12-months follow-up.
Results: Body mass index (BMI) went down from 45.2 ± 6.5 preoperatively to 37.2 ± 5.6 (p < 0.001) at three months and 32.2 ± 5.3 kg/m2 (p < 0.001) at 12 months. SAT went down from 55.0 ± 14.0 L (liter) to 42.2 ± 13.3 L (p < 0.001) at three months and 31.7 ± 10.5 L (p < 0.001) at 12 months (- 42.3%). VAT went down from 6.5 ± 2.3 to 4.5 ± 1.7 (p < 0.001) at three months and 3.1 ± 1.7 L (p < 0.001) at 12 months (- 52.3%). SM went down from 22.7 ± 4.8 to 20.4 ± 3.6 (p = 0.008) at three months and remained 20.2 ± 4.6 L at 12 months (p = 0.17 relative three-month; p = 0.04 relative preop, - 11.1%). Relative loss was higher for VAT than that for SAT (52.3 ± 18.2% vs. 42.3 ± 13.8%; p = 0.03). At 12 months, there was no difference between LSG and RYGB for relative changes in BMI or body tissue composition.
Conclusion: Postoperatively, there was higher net loss of SAT but higher relative loss of VAT with weight loss. SM was lost only during the first three months. MRI provides accurate evaluation of surgeries' effect on individual patients' tissue composition. This can benefit risk assessment for related cardiovascular and metabolic health but cost-related factors will likely reserve the used methods for research.
Keywords: Adipose tissue; Fat volume; Image processing; Laparoscopic sleeve gastrectomy; MRI; Muscle volume; Obesity surgery; Roux-en-Y gastric bypass; Segmentation; Weight loss.