OBJECTIVES : To assess the adoption of changes and trends in bio-impedance measures for assessment of body-composition pre- and post-intervention as health outcome after bariatric surgery of obese individuals.

METHODS : 12-year Cohort study with Interrupted time-series analysis (ITSA) and post-intervention linear regression trends using Bio-impedance measurements for assessment of body composition in comparison with weight and BMI measures, using data from 87 obese individuals followed by 12-year with 36 months post bariatric surgery follow up, categorized into two follow-up periods: first day of intervention to 6 months after bariatric surgery and 6 to 36 months after bariatric surgery.

RESULTS : Body-composition assessed using bio-impedance measures showed higher decrease in fat mass (-27,9kg≈-22,7% and -29,7kg≈-23,3%) after bariatric surgery and increase in total body-water (-5,24kg≈+36,27% and -6,6kg≈+23,4%)), muscle mass (-4,7kg≈+19,9% and -5,7kg≈+20,7%) and fat-free mass (-6,9kg≈+23,4% and -8,7kg≈+24,0%)) at 6 months and 36 months, respectively. Post-intervention linear trends showed decrease in costs immediately after bariatric surgery (-0.89; CI95% -1.16 – 0.61; p<0.001), but increase in cost after 36 months of bariatric surgery (0.004; CI95% -0.0002 – 0.0098; p=0.06). ITSA post-intervention linear trends showed continuous decrease in bio-impedance measures with decrease of muscle mass (-0.0249; CI95% -0.0922 – 0.0424 and -0.043; CI95% -0.1109 – 0.0249), total body-water (-0.0322; CI95% -0.1151 – 0.0507 and -0.0515; CI95% -0.1334 – 0.0304), fat-free mass (0.0006; CI95% -0.0901 – 0.0914 and 0.006; CI95% -0.1202 – 0.1321), and increase in fat mass (0.0006; CI95% -0.0901 – 0.0914 and 0.006; CI95% -0.1202 – 0.1321) at 6 months and 36 months after bariatric surgery, respectively.

CONCLUSIONS : Bio-impedance measures presented higher precision to evaluate trends in health outcomes changes after bariatric surgery in comparison with only weight and BMI measures. ITSA modelling methodology was accurate and precise tool to assess changes, future effects, and effectiveness of health outcomes in pre-post intervention cohort studies.