Sex- and menopausal status-specific patterns of fat free mass loss and cardiorespiratory fitness after metabolic bariatric surgery: the Stratification of Obesity Phenotypes to Optimize Future Obesity Therapy (SOPHIA) longitudinal cohort
In brief
Premenopausal women lost 24.7% of weight as fat-free mass after surgery
In a 1,022-person cohort, fat-free mass accounted for 24.7% of weight lost at 24 months in premenopausal women, versus 27.1% in men and 28.7% in postmenopausal women. Fitness improved in all groups despite these losses, and changes in fat-free mass were not independently linked to fitness. The findings show weight-loss composition varies, but the clinical impact of that variation remains uncertain.
- Journal
- The American journal of clinical nutrition (Q1)
- Published
- 4 September 2026
- Study design
- Cohort / observational study
- Evidence level
- Level 3, Low (CEBM 3b)
- Authors
- Rieneke van der Meer, Valerie M Monpellier, Ronald S L Liem, Ignace M C Janssen, Eric J Hazebroek, Mireille J Serlie
- PMID
- 42833817
- DOI
- 10.1016/j.ajcnut.2026.101441
Why clinicians should know about it
- Picked for Bariatric and Metabolic Surgery (paper of the day, 8 October 2026): High-quality evidence in a top journal
Abstract
BACKGROUND: Fat-free mass (FFM) loss after metabolic bariatric surgery (MBS) may influence physical function, metabolic health, and quality of life. Whether FFM loss differs by sex and menopausal status and whether it relates to cardiorespiratory fitness (CRF) remain unclear. OBJECTIVES: This study aimed to investigate patterns of FFM loss in males, premenopausal females, and postmenopausal females after MBS and to assess relationships between FFM and CRF before and after surgery. METHODS: In this longitudinal cohort study, individuals undergoing primary MBS with ≥18 mo of follow-up were included. Body weight and FFM were measured preoperatively and at intervals ≤72 mo. CRF was assessed using the Åstrand submaximal bicycle test. Changes in total weight loss (%TWL), FFM, and CRF were analyzed using linear mixed models. Associations between FFM and CRF were analyzed using Kendall's τ and linear mixed models. RESULTS: The study included 1022 individuals: 221 males, 614 premenopausal females, and 187 postmenopausal females. Males exhibited the greatest absolute FFM loss, whereas premenopausal females lost the lowest proportion relative to TWL (%FFM/WL). At 24 mo, %FFM/WL was 24.7% in premenopausal females compared with 27.1% in males and 28.7% in postmenopausal females. Despite substantial FFM reductions, maximal oxygen consumption improved significantly in all groups. FFM correlated positively with CRF at baseline and until 24 mo in males and premenopausal females; however, postoperative FFM changes were not independently associated with CRF (β: -0.004; 95% confidence interval: -0.008, 0.001). CONCLUSIONS: FFM loss after MBS differs by sex and menopausal status: males and postmenopausal females lose a greater proportion of FFM relative to TWL than premenopausal females. Nevertheless, CRF improves across all groups, showing postoperative gains in CRF can occur despite FFM reductions. These findings highlight substantial interindividual variability in the composition of weight loss after MBS, which is not fully explained by biological sex, menopausal status, or baseline adiposity. This trial was registered at Centrale Commissie Mensgebonden Onderzoek (CCMO) as NL751466.018.20 (https://onderzoekmetmensen.nl/en/node/27224/pdf).
Abstract as published, via PubMed.
For healthcare professionals. The summary is generated by AI from the published abstract, and the evidence level is assigned automatically from the study design on the Oxford CEBM hierarchy. Neither is medical advice. Read the full paper before changing practice.