Author(s): CORREIA, J.M., PEZARAT-CORREIA, P., MINDERICO, C., MENDONÇA, G., Institution: FACULDADE DE MOTRICIDADE HUMANA, Country: PORTUGAL, Abstract-ID: 353

INTRODUCTION:
Improving body composition by increasing muscle mass and decreasing fat mass is a common approach for eliciting positive health outcomes and augmenting athletic performance. Many people aiming at modifying body composition combine dietary strategies with regular exercise. We sought to explore the effects of four weeks of time-restricted eating (TRE) vs. regular diet, combined with endurance or resistance training, on body composition of trained young males.
METHODS:
The order of dieting was randomized and counterbalanced, and participants served as their own controls. As in one previous study, a two-week washout period (no specific diet or exercise) separated both conditions. The experimental design consisted of two dietary interventions: (1) four weeks of TRE, in which 100% of energy intake was restricted to a time window of 8-h each day, and (2) four weeks of regular diet (non-TRE), in which 100% of energy intake were freely distributed throughout the 24-h day. Height and body mass were used to calculate body mass index (BMI). Each participant was scanned with dual-energy X-ray absorptiometry at baseline and post-intervention. The participants followed structured training routines during each dietary intervention, with a frequency of 3 times/wk (endurance group: 10 km of continuous heavy-outdoor running + 1 severe running bout of 1000 m; resistance group: 4 sets of maximum repetitions at 85% one-repetition maximum - five multi-joint dynamic full body exercise routine). One-way repeated measures ANOVA was used to determine baseline differences between conditions on body composition variables. ANCOVAs were computed for the change in each variable over time, using baseline measures as covariates.
RESULTS:
There were no significant differences between groups or conditions at baseline. The results from ANCOVA indicate that, in both groups, TRE elicited a greater magnitude of decrease in BMI than the non-TRE condition (F=4.2, p=0.048; ES=0.128). Moreover, we found a significant group main effect on fat-free mass (FFM) (p=0.024) indicating that, regardless of diet, the resistance training group exhibited greater magnitude of change in FFM at post-intervention time point. No other variable (i.e. fat-free mass, absolute or relative fat mass) was affected by either intervention over time.
CONCLUSION:
In conclusion, four weeks of TRE can be used with endurance running or resistance training to elicit BMI reductions in trained young males. However, when compared to that seen with a regular diet, TRE does not offer any additional benefit for potentiating meaningful changes in body composition during the course of 4 weeks of endurance or resistance training.