Title: Assessment of the FTO gene polymorphisms in exercise-trained men and women: the effects of a 4-week hypocaloric higher protein diet on body composition, part I
Authors: Madaline Kenyon1, Sarah Knafo2, Alina Ali2, Cassandra Carson1, Anya Ellerbroek1, Cailey Weaver2, Lia Jiannine1, Tobin Silver1, Corey Peacock1, Jaime Tartar2, Jose Antonio1
1 Department of Health and Human Performance, NSU Florida, Davie FL
2 Department of Psychology and Neuroscience, NSU Florida, Davie FL
* Corresponding author: firstname.lastname@example.org
Variations in the fat mass and obesity-associated gene (FTO) are associated with obesity; however, it is not clear if changes in energy intake affect the adaptive response to caloric restriction in those with the risk variants. The three FTO single nucleotide polymorphisms (SNPs), rs1421085, rs17817449 and rs9939609, are in strong linkage disequilibrium. Thus, the purpose of this investigation was to determine the role of the FTO gene vis-à-vis the effects of a 4-week hypocaloric diet on body composition in exercise-trained men and women. We also assessed several biomarkers derived from a saliva sample (i.e., cortisol, C-reactive protein, alpha-amylase).
Forty-seven exercise-trained men (n=11) and women (n=36) (mean±SD: age 32±9 years; height 169±8 centimeters, body mass index 24.5±2.9, hours of aerobic training per week 4.9±3.8, hours of weight training per week 3.9±2.4, years of training experience 13.4±7.0) completed a 4-week hypocaloric diet (i.e., decrease total calories by ~20% while maintaining a protein intake of ~2.1 g/kg/d). Subjects were instructed to maintain the same training regimen and to decrease energy intake via carbohydrate and/or fat restriction during the treatment period. Body composition was determined pre and post via dual energy x-ray absorptiometry (DXA). Total body water was determined via a multifrequency bioelectrical impedance device (InBody 770). Saliva samples were collected pre and post in order to genotype the participants as well as estimate the concentration of several biomarkers (see part II). All testing was done between 11:30am and 3pm.
Of the 47 subjects, 15 were of normal risk for obesity whereas 32 were carriers of the risk alleles for the FTO gene. Subjects were grouped based on their genotype for the three FTO SNPs (i.e., rs1421085, rs17817449 and rs9939609) due to their strong linkage disequilibrium. We have classified those with the normal obesity risk as “non-risk allele” versus those that carry the “risk allele” (i.e., both heterozygous and homozygous). Both groups experienced a significant decrease in total energy intake (non-risk allele: pre kcal 2081±618, post kcal 1703±495; risk allele: pre kcal 1886±515, post kcal 1502±366). Both groups lost a significant amount of body weight (risk allele change: -1.0±1.2, non-risk allele change: -1.2±1.4) and fat mass (risk allele change: -1.1±0.7, non-risk allele change: -0.9±0.4) with no significant differences between the groups. There were no significant changes in either group for fat free mass or total body water.
In the short-term (i.e., four weeks), exercise-trained men and women consuming a hypocaloric diet that is relatively high in protein experience similar changes in body composition due exclusively to a decrement in fat mass. Furthermore, the changes are similar whether you are at a normal risk or are at higher risk for obesity based on their FTO genotypes.