Does Endurance Training Alter Energy Balance?

An examination of the effects of a training program that maximizes caloric expenditure may help gain a better understanding of potential strategies that may be used in future exercise training programs targeting weight loss.

Purpose The purpose of this study was to explore whether endurance training alters energy balance via changes in resting metabolic rate (RMR), daily energy expenditure (EE) and energy intake (EI) in beginning marathon runners.

Methods Twenty-four individuals (17 females, 7 males; 21 + 0.3 years old) were assigned to one of two groups: 1) endurance (EN; n = 12), or 2) active control (AC; n = 12). The EN group completed 15 weeks of marathon training while the AC group maintained their usual exercise routine. Pre- and post-training primary outcome measures included: estimated VO2max (1.5 mile run/walk time), anthropometric indices, RMR (indirect calorimetry), EE (Actigraph Acceleromters), EI (3-day dietary intake). Additional measures of EE and EI were also obtained during a period of high running volume (Week 10) in both EN and AC groups.

Results At baseline, the EN group had significantly higher estimated VO2max values, and higher EE rates than the AC group. The EN group significantly increased EE during the tenth week of training (p = 0.009), while the AC group did not significantly change from baseline to Week 10. Analyses of post training measurements (Week 14) revealed that both the EN and AC groups significantly increased daily EE from baseline measures (p = 0.005) and both groups decreased time to complete 1.5 miles (p = 0.022). There were no changes in body weight, RMR, or EI (p > 0.05) during the course of the study.

Conclusions The results of this study suggest that beginning runners following a marathon training program may experience an increase in EE without a concomitant increase in EI. Although marathon training improves cardiorespiratory fitness, changes in RMR and body weight do not appear to be likewise affected.