Discussion
obese, FM, weight reduction, overweight, T2DM, weight loss
OBESE
To the best of our knowledge, this is the first experimental investigation that examined how estimated NEAT and NEPA are affected by a 1-year exercise intervention performed at different intensities in T2DM. Our results showed no compensatory decreases in NEPA and estimated NEAT on the non-exercise days following 1-year of exercise training, regardless of training protocol (HIIT/MICT). Moreover, whether an individual attained exercise-derived clinically meaningful reductions in BW or FM did not influence changes in NEPA and NEAT after 1-year of intervention.Although it can be speculated that higher exercise intensities would promote more noticeable behavioral and physiological changes toward reducing NEAT and NEPA, the available evidence regarding this issue is still scarce, with none of the literature addressing the effect of exercise intensity on these compensatory mechanisms in the T2DM population. Indeed, the intensity issue has been previously reviewed by Washburn et al. in a population of healthy/overweight/obese adults, where no evidence was found for the intensity of the exercise influencing NEPA and NEAT following short to medium-term exercise interventions [Another possible explanation for the absence of compensatory mechanisms in estimated NEAT and NEPA may be partially related with the inclusion of both aerobic and resistance training in our protocol. Research has suggested that the compensatory reduction in NEPA is lower after resistance training compared to aerobic exercise [During exercise programs, the achieved weight loss often does not match the expected weight reduction due to potential compensatory mechanisms toward energy saving, such as reductions in NEAT and NEPA that attenuate the overall impact of the EE derived from the exercise sessions. Indeed, these compensations may contribute to the inter-individual variability in weight loss achieved from an exercise intervention, where those having clinically meaningful weight losses (i.e., high responders), potentially having higher changes in NEAT and NEPA when compared to low responders in weight loss. A recent systematic review reported that the participants who lost the most weight were also the ones who compensated the most with decreases in NEAT [In our exercise-based intervention, we observed no compensatory reductions in NEPA and estimated NEAT, after 1-year of intervention, when categorizing participants with T2DM as low or high responders for FM or BW, when compared to non-exercising controls. Conversely, Herrmann et al., using a long-term exercise intervention in overweight and obese adults reported that men who were categorized as low weight loss responders (< 5% weight loss) decreased their NEPA and NEAT levels as well as increased their energy intake to a greater extent when compared with the high responder group (≥ 5%) [This investigation is not without limitations. Since this investigation aimed to assess NEPA and NEAT in free-living conditions, and given the known limitations of gold standard methods, such as indirect calorimetry or doubly labeled water to assess these constructs in the field, we opted to use motion sensors, while acknowledging some validation issues for estimating EE [As a major strength, it is important to highlight that this is the first investigation to explore the impact of different exercise regimes and the inter-individual variability in body composition changes resulting from a 1-year exercise intervention on NEPA and estimated NEAT levels in individuals with T2DM on non-exercise days. This is relevant considering that most studies have reported the combined changes on both exercise and non-exercise days, making it impossible to understand what is happening with NEPA and estimated NEAT on the non-training days following exercise interventions. This issue is even more relevant when longer-term interventions are planned, where exercise attendance rates tend to decrease over time.