Metabolic Effects of Eight Weeks of Intermittent Fasting and Resistance Training in Amateur Body Builders

Abstract

PURPOSE: The aim of our study was to investigate the effects of a modified fasting protocol during resistance training in a healthy amateur body builders. METHODS: 34 amateur body builders participated in this study (age 27±4.2, weight 84.6±6.2). Subjects were randomly assigned to 8 weeks of intermittent fasting (IF) or normal diet (ND). IF subjects consumed 100% of their energy needs from 1pm to 7pm (then they fasting from 8pm to 1pm i.e. 8 hours of feeding and 16 hours of fasting (8/16). Subjects divided they caloric intake in three meals (1pm, 3pm and 7 pm). ND group ingested they caloric intake in three meals consumed at 8am, 1pm and 7pm. Groups are matched for kilocalories consumed. Body composition, resting energy expenditure (REE) and respiratory ratio (RR), circulating testosterone, IGF-1, glucose, Insulin, Adiponectin, Leptin, T3, TSH, cytokines (IL-6, IL-1β, TNF-α), Cholesterol (total, HDL, LDL) and TG were analysed. Moreover 1RM on bench press and leg press were measured. RESULTS: After 8 weeks only IF group showed a significant decrease of FM (pre 10.92±3.51 post 9.38±2.49 Kg) (p<0.005) whilst LBM showed similar slight increase. Same trend was shown by limbs muscle CSA. Maximal strength showed no changes. Total testosterone showed a significant decrease (p<0.05) only in IF group (pre 20.26±6.51, post 18.66±4.25 mmol/L), same trend is observed for IGF-1 (pre 216.94±49.55, post 188.94±32.01 ng/mL). Blood glucose showed no significant changes, whilst there was a significant decrease (p<0.05) of insulin in IF subjects. Adiponectin significant increased (p<0.05) in IF group. Total Leptine decreased only in IF group but difference disappeared when adjusted per kg of fat mass. T3 decreased only in IF whilst TSH showed no change in both groups. All three measured inflammatory cytokines decreased significantly in IF group compared to ND. No significant changes were measured in REE whilst IF showed a little but significant decrease of RR (p<0.05). No significant changes were detected in total cholesterol, HDL, LDL whilst TG decreased in IF group. CONCLUSIONS:Our results suggest that an IF 8/16 could improve health related biomarkers, decrease inflammation and body fat mass and maintain muscle mass. Future studies to address the long term effects of IF in athletes are warranted