The effect of bariatric surgery on gravitational loading and its impact on bone mass

Florêncio Diniz-Sousa; Lucas Veras; Giorjines Boppre; Vítor Devezas; Hugo Santos-Sousa; John Preto; Leandro Machado; João Paulo Vilas-Boas; José Oliveira; Hélder Fonseca

doi:10.1016/j.bone.2021.116153

The effect of bariatric surgery on gravitational loading and its impact on bone mass

Bone. 2021 Dec:153:116153. doi: 10.1016/j.bone.2021.116153. Epub 2021 Aug 18.

Affiliations

¹ Research Centre in Physical Activity, Health and Leisure (CIAFEL), Faculty of Sport, University of Porto, Porto, Portugal; Laboratory for Integrative and Translational Research in Population Health (ITR), Porto, Portugal. Electronic address: joseflorenciosousa@gmail.com.
² Research Centre in Physical Activity, Health and Leisure (CIAFEL), Faculty of Sport, University of Porto, Porto, Portugal; Laboratory for Integrative and Translational Research in Population Health (ITR), Porto, Portugal.
³ General Surgery Department, São João Medical Center, Porto, Portugal.
⁴ Centre of Research, Education, Innovation and Intervention in Sport (CIFI2D), Faculty of Sport, University of Porto, Porto, Portugal; Biomechanics Laboratory (LABIOMEP-UP), University of Porto, Porto, Portugal.

PMID: 34416407
DOI: 10.1016/j.bone.2021.116153

Abstract

Introduction: Mechanical unloading associated with weight loss might be one of the main causes for bariatric surgery (BS) induced bone loss. However, no study has tested this hypothesis through objectively measured accelerometry-derived gravitational loading. We aimed to assess how gravitational loading changes following BS and how this correlates with bone mass losses.

Methods: Twenty-one patients submitted to gastric bypass were assessed before, 1, 6 and 12 months after BS for areal bone mineral density (BMD), calciotropic hormones, sclerostin, body composition and daily physical activity. Gravitational loading was determined as the sum of ground reaction forces assessed by accelerometer which considered the interaction between weight and daily ambulation.

Results: Mechanical stimuli promoted through the significant increase in steps number counterbalanced the gravitational loading decreases derived from the significant weight loss after BS. Gravitational loading volume decreased between pre-BS and 1 month post-BS (-2215 kN·d^-1; p = .023), but remained stable between 6 and 12 months post-BS, despite decreases on hip (-7.0%; p < .001), femoral neck (-8.8%; p < .001) and lumbar spine (-5.2%; p < .001) BMD. Serum sclerostin increased from pre-BS to 1 month post-BS (+0.118 ng·mL^-1; p = .021), returning to pre-BS levels 6 months after surgery. Neither vitamin D nor parathyroid hormone were affected by BS. Weight variation was a predictor of BMD decreases at total hip (R² = 0.06; p = .026) and femoral neck (R² = 0.12; p = .022), whereas daily gravitational loading volume was not. Fat and lean mass changes were also predictors of BMD decrease at total hip (R² = 0.05; p = .031) and femoral neck (R² = 0.14; p = .010), respectively.

Conclusion: Our findings suggest that gravitational loading only decreased during the first month after surgery remaining stable thereafter, and these changes do not seem to explain BS-induced bone loss. The association between weight and bone loss seems to result from other physiological aspects, fat and lean mass loss, rather than from gravitational loading decrease.

Keywords: Bone mineral density; Mechanical loading; Physical exercise; Weight loss surgery.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Bariatric Surgery*
Bone Density
Femur Neck
Gastric Bypass*
Humans
Weight Loss