Examining changes in respiratory exchange ratio within an 8‐week weight loss intervention
Beatty and Melanson JHND Early View
Maintaining weight loss is difficult, partly as a result of accompanying reductions in fat oxidation. The present study examined fat oxidation [reflected by respiratory exchange ratio (RER)] within an 8‐week, self‐led weight loss intervention. Changes in RER, body fat (BF%) and estimated energy expenditure (EE) were examined.
Twenty‐two adults [13 females, nine males; mean (SD) age 34.6 (16.5) years; body mass index 32.0 (4.3) kg m−2] received a self‐directed workbook; twelve were also randomised to receive a self‐monitoring wrist‐worn device. At weeks 0 and 8, RER (indirect calorimetry), BF% (BodPod) and estimated EE [7‐day physical activity recall (PAR‐EE) were collected. Participants were pooled and paired t‐tests were used to examine changes over time. Correlations explored associations among variables. Participants were then dichotomised into weight loss group (WL) or weight stable/gainers group (WSG) and eating behaviours [Intuitive Eating Scale (IES‐2)] were examined by 2 × 2 repeated measures multivariate analysis of covariance.
There were no significant changes in RER, body fat percentage and PAR‐EE. A significant negative association was found between week 8 PAR‐EE and week 8 RER, as well as between BF% change and RER change. There was a significant time by WL versus WSG group effect of IES‐2 scores, with the WL group self‐reporting significantly increased scores in Eating for Physical Reasons rather than Emotional Reasons (EPR) subscale.
Increased physical activity after an 8‐week weight loss intervention was associated with a higher fasting fat oxidation. Participants who increased EPR scores were more successful in weight loss than those without a change in this subscale.