The Effects of High Protein Intakes During Energy Restriction on Body Composition, Energy Metabolism and Physical Performance in Athletes
Creators: name: Kanaan, Mikael
Publisher: name: Université d'Ottawa / University of Ottawa
Year: 2023
Subjects: Metabolism
Protein
Skeletal Muscle
Resistance Exercise
Energy Restriction
Athletes

description: Introduction Weight loss practices are commonly used by athletes who perceive lower levels of body fat and higher fat-free mass (FFM) as advantageous for physical performance. High protein diets have been associated with greater fat loss and greater retention of lean mass during periods of energy restriction (ER) in individuals with obesity. However, less is known about the effects of high protein diets in trained individuals during ER. It has been proposed that leaner individuals are more at risk of losing FFM during ER than individuals with overweight. The current ACSM recommendation for protein intake in active individuals is 1.2-1.7g/kg. However, it is unclear whether higher intakes are necessary to maximize FFM retention and maximize physical performance in athletes undergoing periods of ER. Objective Our primary objective was to determine whether high protein intakes could maximize FFM retention in trained individuals during periods of ER. We also aimed to determine whether higher protein intakes are superior at maintaining physical performance. Lastly, we aimed to determine whether high protein intakes could mitigate adaptive thermogenesis (AT) in response to ER. Methods Twelve college aged athletes (6 women and 6 men) from various sports were analyzed in this study. They underwent a 6-week 25% reduction in energy intake along side a 3-day full body resistance training program. Participants were randomly assigned to a low (~1.2g/kg), moderate (~1.6g/kg) or high (~2.2g/kg) protein group. Baseline and post-intervention measures were obtained via Dual X-ray absorptiometry (DXA), isotopic water dilution, indirect calorimetry, dietary records and strength based physical testing. Results Our results indicate a main effect of the intervention on fat mass reductions (19.66 ± 9.05 kg vs 18.02 ± 8.07 kg) (p = 0.016) despite non-significant reductions in body weight (p = 0.059). No significant changes in FFM were observed (p = 0.307). Significant increases in chest press 5RM strength (43.18 ± 14.95 kg vs 48.86 ± 17.46 kg) and chin-up maximal repetition (4.75 ± 5.64 vs 6.08 ± 6.56) were observed across all groups from baseline to post-intervention (p &lt; 0.05). No significant increases in strength were noted on lower body movements. Resting energy expenditure (REE) was significantly reduced after the 6-week intervention (1743.52 ± 295.74 kcal vs 1655.18 ± 263.23 kcal) (p = 0.006). What is more, post-intervention measured and predicted REE were also significantly different (1655.18 ± 263.23 kcal vs 1747.92 ± 263.20) (p = 0.012). No significant effects of protein were noted on any of the outcomes. Conclusion Our preliminary results indicate that the ACSM recommendation of 1.2-1.7g/kg is sufficient for most athletes even during periods of ER to maintain FFM and physical performance. We also found the possibility of early AT in that population independently of protein intake. In fact, REE was reduced by ~100 kcal/day more than predicted despite minimal weight loss and relative preservation of FFM.