Changes in Fat Mass Index and Fat-Free Mass Index Vary Significantly by Age and Sex of the Patient, and by Type of Bariatric Surgery Publisher Pubmed



Hassan Zadeh M¹ ; Fatemi SF¹ ; Rezvani R¹ ; Mohammadi Farsani G^{2, 3} ; Pazouki A^{3, 4} ; Zamaninour N³ Show Affiliations
Source: Obesity Surgery Published:2024

Abstract

Background: The loss of fat-free mass after rapid weight loss following bariatric surgery shows BMI is inadequate for reporting weight loss, emphasizing the need for a more accurate body composition metric. This study assessed changes in fat mass index (FMI), fat-free mass index (FFMI), and dietary intake over 6 months after one-anastomosis gastric bypass (OAGB), Roux-en-Y gastric bypass (RYGB), and sleeve gastrectomy (SG) across age and sex groups. Materials and Methods: This prospective observational study included 151 bariatric surgery candidates. Data on demographics, anthropometric, body composition, and food intake data were collected before and 6 months after surgery. SPSS version 22 was used for analysis, employing ANOVA and t-tests to assess group differences. Results: Younger patients (≤ 35 years) had higher percent total and excess weight loss (%TWL and %EWL) across all bariatric surgeries, and those undergoing SG experienced more favorable changes in fat-free mass (FFM) and visceral fat compared to other procedures (P = 0.002). Males had higher percent change in fat mass index (%∆ FMI) and visceral fat than females with OAGB and RYGB (P < 0.05). Women undergoing SG and RYGB had a more significant decrease in energy intake compared to OAGB (P < 0.001), and the ≤ 35 and 35–44 age groups demonstrated lower reductions in energy intake following OAGB. Conclusion: Age, sex, and surgery type significantly affect bariatric surgery outcomes. Younger patients achieved greater weight-related improvements, while men undergoing RYGB experienced more substantial fat mass changes than women. Graphical Abstract: (Figure presented.) © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.