title: Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males.
abstract: Intermittent fasting (IF) is an increasingly popular dietary approach used for weight loss and overall health. While there is an increasing body of evidence demonstrating beneficial effects of IF on blood lipids and other health outcomes in the overweight and obese, limited data are available about the effect of IF in athletes. Thus, the present study sought to investigate the effects of a modified IF protocol (i.e. time-restricted feeding) during resistance training in healthy resistance-trained males.
  
  
  
  Thirty-four resistance-trained males were randomly assigned to time-restricted feeding (TRF) or normal diet group (ND). TRF subjects consumed 100 % of their energy needs in an 8-h period of time each day, with their caloric intake divided into three meals consumed at 1 p.m., 4 p.m., and 8 p.m. The remaining 16 h per 24-h period made up the fasting period. Subjects in the ND group consumed 100 % of their energy needs divided into three meals consumed at 8 a.m., 1 p.m., and 8 p.m. Groups were matched for kilocalories consumed and macronutrient distribution (TRF 2826 ± 412.3 kcal/day, carbohydrates 53.2 ± 1.4 %, fat 24.7 ± 3.1 %, protein 22.1 ± 2.6 %, ND 3007 ± 444.7 kcal/day, carbohydrates 54.7 ± 2.2 %, fat 23.9 ± 3.5 %, protein 21.4 ± 1.8). Subjects were tested before and after 8 weeks of the assigned diet and standardized resistance training program. Fat mass and fat-free mass were assessed by dual-energy x-ray absorptiometry and muscle area of the thigh and arm were measured using an anthropometric system. Total and free testosterone, insulin-like growth factor 1, blood glucose, insulin, adiponectin, leptin, triiodothyronine, thyroid stimulating hormone, interleukin-6, interleukin-1β, tumor necrosis factor α, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides were measured. Bench press and leg press maximal strength, resting energy expenditure, and respiratory ratio were also tested.
  
  
  
  After 8 weeks, the 2 Way ANOVA (Time * Diet interaction) showed a decrease in fat mass in TRF compared to ND (p = 0.0448), while fat-free mass, muscle area of the arm and thigh, and maximal strength were maintained in both groups. Testosterone and insulin-like growth factor 1 decreased significantly in TRF, with no changes in ND (p = 0.0476; p = 0.0397). Adiponectin increased (p = 0.0000) in TRF while total leptin decreased (p = 0.0001), although not when adjusted for fat mass. Triiodothyronine decreased in TRF, but no significant changes were detected in thyroid-stimulating hormone, total cholesterol, high-density lipoprotein, low-density lipoprotein, or triglycerides. Resting energy expenditure was unchanged, but a significant decrease in respiratory ratio was observed in the TRF group.
  
  
  
  Our results suggest that an intermittent fasting program in which all calories are consumed in an 8-h window each day, in conjunction with resistance training, could improve some health-related biomarkers, decrease fat mass, and maintain muscle mass in resistance-trained males.
authors.affiliation: Department of Biomedical Sciences, University of Padova, Padua, Italy.
authors.forename: Tatiana
authors.identifier: 0000-0002-1404-1511
authors.initials: T
authors.lastname: Moro
authors.affiliation: Department of Kinesiology & Sport Management, Texas Tech University, Lubbock, TX, USA.
authors.forename: Grant
authors.identifier: 0000-0002-0230-6586
authors.initials: G
authors.lastname: Tinsley
authors.affiliation: Sport and Exercise Sciences Research Unit, University of Palermo, Palermo, Italy.
authors.forename: Antonino
authors.identifier: 0000-0001-8334-6581
authors.initials: A
authors.lastname: Bianco
authors.affiliation: Department of Biomedical Sciences, University of Padova, Padua, Italy.
authors.forename: Giuseppe
authors.identifier: 0000-0002-2768-3257
authors.initials: G
authors.lastname: Marcolin
authors.affiliation: Department of Biomedical Sciences, University of Padova, Padua, Italy.
authors.forename: Quirico Francesco
authors.initials: QF
authors.lastname: Pacelli
authors.affiliation: Sport and Exercise Sciences Research Unit, University of Palermo, Palermo, Italy.
authors.forename: Giuseppe
authors.identifier: 0000-0002-7758-7175
authors.initials: G
authors.lastname: Battaglia
authors.affiliation: Sport and Exercise Sciences Research Unit, University of Palermo, Palermo, Italy.
authors.forename: Antonio
authors.identifier: 0000-0002-5387-468X
authors.initials: A
authors.lastname: Palma
authors.affiliation: College of Physical Education and Dance, Federal University of Goias, Goiania, Brazil.
authors.forename: Paulo
authors.identifier: 0000-0003-2459-4977
authors.initials: P
authors.lastname: Gentil
authors.affiliation: Italian Fitness Federation, Ravenna, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Neri
authors.affiliation: Department of Biomedical Sciences, University of Padova, Padua, Italy. antonio.paoli@unipd.it.
authors.forename: Antonio
authors.identifier: 0000-0003-0474-4229
authors.initials: A
authors.lastname: Paoli
mesh_terms: D000328:Adult; D001481:Basal Metabolism; D031204:Caloric Restriction; D002318:Cardiovascular Diseases / Q000378:metabolism* / Q000473:pathology*; D005247:Feeding Behavior; D006801:Humans; D007249:Inflammation / Q000473:pathology*; D008297:Male; D053580:Muscle Strength; D055070:Resistance Training; D012307:Risk Factors; D013997:Time Factors
keywords: Body builders; Body composition; Fasting; Intermittent fasting; Resistance training; Time-restricted feeding