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Randomized Controlled Trial
. 2025 May 30;23(1):317.
doi: 10.1186/s12916-025-04143-6.

Increased weight-load improves body composition by reducing fat mass and waist circumference, and by increasing lean mass in participants with obesity: a single-centre randomised controlled trial

Jakob Bellman  1 , Klaas Westerterp  2 , Loek Wouters  2 , Marit Johannesson  3 , Niklas Lundqvist  3 , Joel Kullberg  4   5 , Christel Larsson  6 , Mikael Gustafsson  6 , Stefan Pettersson  6 , Jonatan Fridolfsson  6 , Daniel Arvidsson  6 , Mats Börjesson  6   7 , Dan Curiac  8 , John-Olov Jansson  9 , Per-Anders Jansson  8   10 , Claes Ohlsson  11   12
Affiliations
Randomized Controlled Trial

Increased weight-load improves body composition by reducing fat mass and waist circumference, and by increasing lean mass in participants with obesity: a single-centre randomised controlled trial

Jakob Bellman et al. BMC Med. .

Abstract

Background: To investigate the effects of increased weight-loading on body weight, body composition, fat mass distribution, physical activity and energy balance in individuals with obesity.

Methods: This single-centre non-blinded randomised controlled trial was conducted from August 1, 2021, through February 28, 2022. Adults with obesity class 1 (body mass index, BMI 30-35 kg/m2) were assigned to wear either a heavy (high load; 11% of body weight, n = 28) or light (low load; 1% of body weight, n = 30) weight vest for 8 h per day over 5 weeks.

Results: High-load treatment reduced fat mass (mean difference - 2.60%; 95% CI - 3.79, - 1.41) and increased lean mass (mean difference 1.40%; 95% CI 0.37, 2.42), with no significant effect on body weight. Fat mass reductions were primarily observed in weight-loaded regions but not in the non-weight-bearing regions such as the arms. Waist circumference decreased (mean difference - 2.26%; 95% CI - 3.81, - 0.71) in the high-load group compared to the low-load group. Despite these beneficial changes, sedentary time was higher in the high-load group (mean difference 4.69%; 95% CI 0.98, 8.39) compared to the low-load group, while energy expenditure and energy intake remained unchanged.

Conclusions: Increased weight-loading reduced fat mass and increased lean mass, resulting in a healthier body composition. These effects were achieved despite no increase in physical activity. The fat mass-reducing effect was primarily seen in weight-loaded regions, implying local adaptation to the increased loading.

Trial registration: Registered at ClinicalTrials.gov (NCT04697238) in 2021.

Keywords: Body composition; Energy balance; Fat mass distribution; Obesity; Standing position; Weight-bearing; Weight-loading.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: The trial was approved by the Swedish Ethical Review Authority (registration number 2021–00095) and was conducted in accordance with the Declaration of Helsinki and the International Conference on Harmonization Guidelines (ICH) for Good Clinical Practice (GCP). All participants provided written informed consent before undertaking any study procedures. Competing interests: The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
CONSORT Diagram describing enrolment and study flow. The participants with screening failure did not meet all the inclusion criteria and/or did meet at least one of the exclusion criteria. SAE, severe adverse event
Fig. 2
Fig. 2
Schematic timeline showing key moments of the trial. Screening performed on day -21. Baseline measurements obtained between day -21 and day 0 (Measurement 1). Measurement 1 included 14-day DLW measurement (day -14), 7-day accelerometer measurement (day -13), DXA and CT scans along with SDQ on day 0. Randomisation on day 0 and treatment with either low load or high load between day 0 and day 35. Second measurement period (Measurement 2) performed between day 14 and day 35. Measurement 2 included 14-day DLW measurement (day 14), 7-day accelerometer measurement (day 15), SDQ (day 28) along with DXA and CT scans on day 35. Follow-up visit on day 49, 2 weeks after the end of treatment. Figure created in BioRender; Bellman, J. (2025) https://BioRender.com/y79d008. CT, computed tomography; DLW, doubly labelled water; DXA, dual-energy X-ray absorptiometry; SDQ, Short Dietary Questionnaire
Fig. 3
Fig. 3
Change in body weight (BW), fat mass, lean mass and bone mineral content (BMC) at 5 weeks vs. baseline for all participants who completed the trial according to protocol. Participants treated with light weight vest (low load; n = 26) or heavy weight vest (high load, n = 25). Body composition and BMC measured with dual-energy X-ray absorptiometry (DXA). Results are presented as estimated marginal means with error bars showing 95% confidence intervals. The between-group P-values (high load vs low load) are calculated using analysis of covariance (ANCOVA) adjusted for age, sex, baseline body mass index (BMI), vest exposure (h) and standing % with vest. *P < 0.05, ***P < 0.001
Fig. 4
Fig. 4
Percentage change in different regions fat mass at 5 weeks vs. baseline for all participants who completed the trial according to protocol. Participants treated with light weight vest (low load; n = 26) or heavy weight vest (high load, n = 25). Body composition measured with dual-energy X-ray absorptiometry (DXA). Results are presented as estimated marginal means with error bars showing 95% confidence intervals. The between-group P-values (high load vs low load) are calculated using analysis of covariance (ANCOVA) adjusted for age, sex, baseline body mass index (BMI), vest exposure (h) and standing % with vest. *P < 0.05, **P < 0.01, ***P < 0.001
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