The effects of exercise session timing on weight loss and components of energy balance: midwest exercise trial 2

International Journal of Obesity https://doi.org/10.1038/s41366-019-0409-x ARTICLE Behavior, Psychology and Sociology The effects of exercise session timing on weight loss and components of energy balance: midwest exercise trial 2 Erik A. Willis1,2 Seth A. Creasy ● 3 ● Jeffery J. Honas4 Edward L. Melanson3,5,6 Joseph E. Donnelly4 ● ● 1234567890();,: 1234567890();,: Received: 17 October 2018 / Revised: 17 April 2019 / Accepted: 1 May 2019 © This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply 2019. This article is published with open access Abstract Background/objectives Circadian physiology has been linked to body weight regulation and obesity. To date, few studies have assessed the association between exercise timing and weight related outcomes. The aim of this secondary analysis was to explore the impact of exercise timing (i.e., 24 h clock time of exercise session) on weight loss and components of energy balance. Subjects/methods Overweight/obese (BMI 25.0–39.9 kg/m2), physically inactive, young adults (~51% female) completed a 10-month supervised exercise program (400 or 600 kcal/session for 5 days/week) or served as non-exercise controls (CON). Participants were categorized based on the time of day in which they completed exercise sessions (Early-Ex: >50% of sessions completed between 7:00 and 11:59 am; (n = 21), Late-Ex: >50% of sessions completed between 3:00 and 7:00 pm; (n = 25), Sporadic-Ex: <50% of sessions completed in any time category; (n = 24), and CON; (n = 18)). Body weight, energy intake (EI; digital photography), and non-exercise physical activity (NEPA; accelerometer) were assessed at baseline, 3.5, 7, and 10 months. Total daily energy expenditure (TDEE; doubly labeled water), was assessed at baseline and 10 months. Results At month 10, weight loss was significantly greater in both Early-EX (−7.2 ± 1.2%; p < 0.001) and Sporadic-EX (− 5.5 ± 1.2%; p = 0.01) vs CON (+0.5 ± 1.0%), and Early-EX vs Late-EX (−2.1 ± 1.0%; p < 0.001). There were no between group differences for change in TDEE, EI, and non-exercise energy expenditure (P > 0.05). A significant group × time interaction (p = 0.02) was observed for NEPA (counts/min), however, after adjusting for multiple comparisons, group effects were no longer significant. Conclusions Despite minimal differences in components of energy balance, Early-EX lost significantly more weight compared with Late-Ex. Although the mechanisms are unclear, the timing of exercise may be important for body weight regulation. Introduction Supplementary information The online version of this article (https:// doi.org/10.1038/s41366-019-0409-x) contains supplementary material, which is available to authorized users. High volumes of exercise are associated with weight loss and the prevention of weight gain [1]. In fact, studies utilizing supervised exercise, to confirm the completion of the * Erik A. Willis 4 Department of Internal Medicine, The University of Kansas Medical Center, Kansas City, KS, USA 1 Center for Health Promotion and Disease Prevention, University of North Carolina-Chapel Hill, Chapel Hill, NC, USA 5 2 Division of Epidemiology and Genetics, Metabolic Epidemiology Branch, National Cancer Institute, Bethesda, MD, USA Division of Geriatric Medicine, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, USA 6 Eastern Colorado VA Geriatric Research, Education, and Clinical Center, Denver, CO, USA 3 Division of Endocrinology, Metabolism, and Diabetes, Anschutz Medical Campus, University of Colorado Aurora, Aurora, CO, USA E. A. Willis et al. recommended dose of exercise, have found that engaging in >250 min of exercise per week elicits clinically significant weight loss (>5%) [2–5]. However, there are large interindividual differences in weight loss despite participants engaging in similar amounts of exercise [6–11]. It has been postulated that these differences in weight loss are owing to biological (e.g., reductions in resting metabolic rate (RMR) and total daily energy expenditure (TDEE)) and behavioral (e.g., changes in non-exercise physical activity (NEPA) or energy intake (EI)) compensation, resulting in less weight loss than theoretically predicted by the amount of energy expended from exercise [12–14]. However, the literature regarding biological or behavioral changes in response to exercise is inconclusive and conflicting [15–19]. More recently, evidence has suggested that the timing of exercise may play a critical role in body weight regulation [20–22]. However, the contribution of timing of exercise, within the 24 h day, to exercise induced weight loss is unclear. Circadian physiology has been linked to body weight regulation and obesity [23]. The circadian system has been shown to play an important role in regulating daily rhythms of metabolism, sleep/wake cycle, feeding behavior, and hormonal secretions [24]. Most evidence for the role of circadian rhythms and body weight regulation is related to the timing of EI [25–29] and sleep/wake cycle [21, 23, 30–32]. To date, the few studies that have assessed the association between exercise timing and weight related outcomes have been limited by study design and the lack of objective assessment methods [20–22]. Owing to the high levels of variability in exercise induced weight loss, further understanding the role of exercise timing could be important to maximize weight loss efforts. In this secondary analysis, data from the recently completed Midwest Exercise Trial 2 (MET-2) afforded an opportunity to assess whether timing of exercise had differential effects on changes in weight, EI, RMR, non-exercise energy expenditure (NExEE), NEPA, and sedentary time in men and women in response to a 10month supervised exercise training program with verified levels of exercise energy expenditure (ExEE). Methods Participants were recruited into MET-2 (Registration Clinical Trial number: NCT01186523, www.clinicaltrials.gov) and provided written informed consent before engaging in any aspect of the trial and were compensated for participation. The approval for this study was obtained from the human subjects committee of the University of KansasLawrence. Briefly, MET-2 was a 10-month randomized efficacy trial, 5 day/week supervised exercise intervention at two levels of ExEE (400 or 600 kcal/session) or nonexercise control that was designed to evaluate the effect of aerobic exercise, without energy restriction, on weight loss in sedentary overweight and obese men and women. Blinding of participants to group assignment was not possible. Investigators and research assistants were blinded at the level of outcome assessments and data entry [16, 33]. A detailed description of the design and methods for MET-2 [33], results for the primary outcome [6], changes in NExEE and NEPA [16], and differences between intervention responders and non-responders have been published [34 (...truncated)