Intermittent normobaric hypoxia alters substrate partitioning and muscle oxygenation in individuals with obesity: implications for fat burning

Abstract

This single-blind, crossover study aimed to measure and evaluate the short-term metabolic responses to continuous and intermittent hypoxic patterns in individuals with obesity. Indirect calorimetry was used to quantify changes in resting metabolic rate (RMR), carbohydrate (CHOox, %CHO) and fat oxidation (FATox, %FAT) in nine individuals with obesity pre- and post-: (i) breathing normoxic air [normoxic sham control (NS-control)]; (ii) breathing continuous hypoxia (CH); or (iii) breathing intermittent hypoxia (IH). A mean peripheral oxygen saturation (SpO2) of 80-85% was achieved over a total of 45 minutes of hypoxia. Throughout each intervention pulmonary gas exchanges - oxygen consumption ( ), carbon dioxide production ( - and deoxyhaemoglobin concentration ( [HHb]) in the vastus lateralis were measured. Both RMR and CHOox measured pre- and post-interventions were unchanged following each treatment: NS-control; CH; or IH (all p > 0.05). Conversely, a significant increase in FATox was evident between pre- and post-IH (+44%, p = 0.048). While the mean [HHb] values significantly increased during both IH and CH ( p<0.05), the greatest zenith of [HHb] was achieved in IH compared to CH ( p = 0.002). Furthermore, there was a positive correlation between ∆[HHb] and the shift in FATox measured pre- and post-intervention. It is suggested that during IH the increased bouts of muscle hypoxia, revealed by elevated ∆[HHb], coupled with cyclic periods of excess post-hypoxia oxygen consumption (EPHOC, inherent to the intermittent pattern) played a significant role in driving the increase in FATox post-IH.