Effects of Nutrient Timing on Protein Synthesis, Markers of Health and Fitness in Free Living Overweight Post Menopausal Women in a Resistance Interval Program Training (RIPT) and Weight Loss Intervention

Abstract

This study examined whether immediate (I) vs. delayed (D) protein intake following exercise influenced fractional synthesis rate (FSR) and other health/fitness markers during a Resistance Interval Program (RIPT) exercise & weight management intervention. 21 sedentary women (59.8±5 yrs, 43.7±3% body fat, 31.0±3 kg/m²) participated in a 12 week Curves Complete® program [followed an energy-reduced diet (1,500 kcal/d; 30% C, 45% P, and 25% F) while participating in circuit resistance exercise (RE) (30min; 3d/wk) and walking (10k steps, 4/d wk)]. Each ingested 15 g of protein immediately post (I) or 2 hours post (D) RE. Body composition, body mass, resting energy expenditure (REE) and FSR [determined using a deuterium oxide (²H₂O or D₂O) ingestion and muscle biopsy protocol] were examined. Data were analyzed by repeated measures MANOVA and/or ANOVA, and are presented as changes from baseline after 4, 8, and 12 wks [body composition, body mass, resting energy expenditure (REE)]; 0 and 12 weeks (FSR) for the I and D groups, respectively. Significant time effects were observed (body mass, fat mass, and body fat) yet no significant group x time effects resulted. The D group generally experienced more favorable body mass (I -2.0±1.0, -2.7±1.6, -3.6±2.2; D -2.2±2.5, -3.6±3.6, - 4.2±4.2, kg, p=0.59), fat mass (I -1.7±1.0, -2.4±1.5, -3.5±1.5; D -2.8±1.7, -3.4±2.6, - 4.8±3.3, kg, p=0.32), FFM (I -0.3±2.0, -0.1±2.0, -0.0±1.7; D 0.92±1.4, 0.4±1.7, 1.1±1.3, kg, p=0.24), and % body fat (I -1.2±2.1, -1.8±2.1, -2.8±1.9; D -2.6±1.9, -2.8±2.6, - 4.4±3.1 %, p=0.25) changes. No REE differences were seen among groups (I -18±146, - 101±163, -82±126; D -46±137, -17±173, -90±142 kcal/d, p=0.34). No significant nutrient timing x training interactions (mean±SEM) were observed in muscle FSR expressed as percent/day of the alanine pool (I-Pre 13.6±4.3, I-Post 21.1±4.3; D-Pre 15.6±4.0, D-Post 23.8±4.0 %/d, p=0.93). However, FSR was upregulated (p<0.05) in response to a pre-training bout of RE (14.6±2.9 %/d), and trended 54% higher (p=0.075) in response to post-training values (22.5±2.9 %/d). Results indicate that the program was effective in promoting weight and fat loss, while maintaining FFM. Post exercise FSR increased pre-training, and trended higher at 12-wks. However, while some trends were observed warranting additional study, no statistically significant differences were seen between the I and D nutrient timing strategies.