BACKGROUND: The American College of Sports Medicine recommends 300 minutes of moderate or 150 minutes of vigorous physical activity (MVPA) per week, in combination with proper nutrition, to obtain substantial health benefits and weight loss. Fasting dietary strategies, such as time-restricted eating (TRE), combined with resistance exercise have been shown to reduce fat mass and maintain or increase lean mass. Concurrent exercise, the inclusion of aerobic and resistance exercise, and TRE may be a valid method for preserving lean mass during weight loss while simultaneously reducing disease risk and improving functional performance. OBJECTIVE: The purpose of this investigation was to determine whether average time spent in MVPA, an indicator of concurrent exercise training volume, was a predictor of fat mass loss in physically inactive overweight and obese females following an eight-week dietary and concurrent exercise intervention, regardless of dietary group allocation. We hypothesized that MVPA will predict decreases in fat mass observed during the intervention. METHODS: Stepwise linear regression determined the relationship between MVPA and fat mass loss. A total of 18 females (mean ± SD; age 43.7 ± 7.3 years; BMI 29.7 ± 2.3 kgm2 ) were included in the analysis. Body and fat mass were assessed pre- and post-exercise and dietary intervention using dual-energy x-ray absorptiometry. Dietary intakes were estimated using three-day dietary logs and ESHA software at weeks one, four, and seven. Dietary group allocation was recorded as "1" for TRE and "0" for normal eating. Dietary group, age (years), height (cm), pre-intervention body and fat mass (kg), average time spent in MVPA (min/week), average energy intake (kcal/day), and average carbohydrate, fat, and protein intake (g/day) were included in the analysis. Age was self-reported and MVPA was assessed at weeks two, five, and eight using accelerometry. RESULTS: Our model explained 55.7% of the variance in fat mass changes (F2, 15 = 9.424; p = 0.002). Stepwise analysis indicated that reductions in fat mass were predicted first by participation in TRE (β ± SE; -1.739 ± 0.451; p = 0.002) and then by time spent in MVPA (β ± SE; -0.004 ± 0.002; p = 0.044). CONCLUSION: Time spent in MVPA and TRE were predictors of fat mass loss following eight weeks of dietary and concurrent exercise intervention. The significance of MVPA to the model indicates that concurrent exercise contributes to fat loss regardless of dietary pattern. © FASEB.
