Byrd, Michael James (2017-12). 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. Doctoral Dissertation. Thesis uri icon

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(R) 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.

publication date

  • December 2017