Igf2 G3579c Polymorphism and Adiposity Associate with Adherence to A Resistance Training Program

PURPOSE: Genetic variation in insulin-like growth factor 2 (IGF2), a peptide hormone within the IGF system, is associated with adiposity in adult males. Genetic variants have not been identified to explain exercise adherence, though 50% of the variability in adulthood physical activity levels is due to genetic factors. Thus, we examined if the IGF2 G3579C polymorphism (IGF2 GC) and adiposity associated with adherence to a resistance training (RT) program. METHODS: Subjects were 649 (mean ± SEM, 24.5 ± 0.2 yr) mostly white (78%), men (41%) and women (59%) with a body mass index (BMI) of 24.7±0.7 kg/m2 and had not performed RT in the previous yr. Subj ects enrolled in a 12 wk (2 d/wk) supervised unilateral upper-arm RT program. Exercise adherence was categorized into two groups: completers (n=597, completed 24 RT sessions) and drop outs (DO) (n=52, seceded prior to completing 24 RT sessions with a mean of 9.0 ± 0.9 sessions completed). Adiposity was categorized by BMI as normal weight (n=400, NW=21.9 ± 0.1 kg/m2) and overweight (n=249, OW=29.2 ±0.3 kg/m2). Chi-Square (χ2) tested for differences in exercise adherence among IGF2 GC genotype and adiposity groups. RESULTS: More IGF2 CC homozygotes (n=1 93) did not complete the RT program compared to carriers of the IGF2 G allele (n=456, GC/GG), 13.0 vs 5.9% DO, respectively (p<0.01). In addition, more NW subjects with the IGF2 CC genotype (n=1 10, 22.0 ± 0.1 kg/m2) did not complete the RT program than NW carriers of the IGF2G allele (n=283, 21.9 ±0.1 kg/m2), 10.0 vs 4.0% DO (p<0.05). Exercise adherence was not associated with IGF2 GC genotype in the OW subjects (p>0.05). CONCLUSIONS: NW adults with the IGF2 G allele appear to be more likely to adhere to an RT program than those with the IGF2 CC genotype. However, no association between the IGF2 GC genotype and exercise adherence was found in OW subjects. Further work is needed to determine the pathways through which IGF2 GC genotype and adiposity may associate with exercise adherence.