Comparison of time-matched aerobic, resistance or combined exercise training in women living with obesity: a protocol for a pilot randomised controlled trial—the EXOFFIT (Exercise for Obesity in Females to increase Fitness) study

INTRODUCTION: Obesity in women has more than doubled in the past thirty years. Increasing research suggests that increased cardiorespiratory fitness (CRF) can largely attenuate the negative health risks associated with obesity. Though previous literature suggests that combined training may be the most effective for improving CRF in adults with obesity, there is minimal research investigating the efficacy of combined and resistance programmes in women with obesity. This article outlines a protocol for a parallel pilot study which aims to evaluate the feasibility and efficacy of three exercise modalities in women with obesity for increasing CRF and strength and improving body composition and other health outcomes (i.e. quality of life). METHODS AND ANALYSIS: Sixty women (aged 18–50) with obesity (body mass index [BMI] ≥ 30 and/or waist circumference ≥ 88 cm) who are physically inactive, have no unstable health conditions and are safe to exercise will be recruited from September 2021 to December 2022. The main outcome will be feasibility and acceptability of the intervention and procedures. Trial feasibility outcomes will be evaluated to determine if a definitive trial should be undertaken. Trial acceptability will be explored through follow-up qualitative interviews with participants. Secondary outcomes will include CRF (predicted VO(2) max), anthropometrics (i.e. BMI), strength (5RM bench press, leg dynamometry, grip strength) and other health outcomes (i.e., pain). Participants will be block randomised into one of four trial arms (aerobic exercise, resistance training and combined training groups, non-active control group) and measurements will be completed pre- and post-intervention. The exercise groups will receive an individualised supervised exercise programme for 3× sessions/week for 12 weeks. The change in mean values before and after intervention will be calculated for primary and secondary outcomes. ANOVA and t-tests will be applied to evaluate within-group and between-group differences. If sufficient participants are recruited, the data will be analysed using ANCOVA with the age and BMI as covariates. DISCUSSION: This pilot will provide data on the feasibility and acceptability of trial procedures and of the programmes’ three progressive time-matched exercise interventions (aerobic, resistance and combined) for women living with obesity, which will help inform future research and the potential development of a full-scale randomised clinical trial. TRIAL REGISTRATION: ISRCTN, ISRCTN13517067. Registered 16 November 2021—retrospectively registered.