Impact of obesity on central processing time rather than overall reaction time in young adult men.

BACKGROUND AND PURPOSE: The association between weight status with simple cognitive tasks such as reaction time (RT) may not be observed in young people as cognitive functioning development has reached its peak. In the present study, we aimed to examine the association between overall and central adiposity with overall and central processing of RT in a sample of young adult men with different weight status from Ardabil, Iran. METHODS: Eighty-six young males between June-July 2018 completed RT tests as well as premotor time (PMT) using surface electromyography changes in isometric contraction response to an audio stimulus. RESULTS: No significant associations were observed between RT and PMT and different body mass index categories (underweight, normal weight, overweight and obese), as well as fat mass and fat to skeletal muscle mass ratio quartiles (Q). However, participants with greater waist to height ratio (WHtR) had longer PMT (but not RT) than their peers with lower WHtR (Q3 than Q2 and Q1 groups; p < 0.05, d = 1.23). Participants in the skeletal muscle mass quartile Q2 tended to have longer RT than participants in Q3 in an adjusted comparison model (p = 0.05, d = 0.72). CONCLUSIONS: Although the association between weight status and RT might be elusive in young adults, our results show that higher central adiposity is negatively associated with PMT in young adults. Longitudinal studies are needed to explore the changes in obesity indexes and process speed in longer terms. LEVEL OF EVIDENCE: Level I, experimental study.

Association Between Weight Status and Executive Function in Young Adults.

Background and objectives: To explore the association between weight status and executive function in young adults. Materials and Methods: Ninety-seven young males (age 17-26 years) underwent adiposity and body composition measurements using body composition analyzer. Inhibitory control and working memory were measured using the Cambridge Neuropsychological Test Battery (CANTAB). Results: Multiple linear regression using both unadjusted and adjusted analyses revealed no association between adiposity and body composition variables with executive tasks, apart from a significant association between skeletal muscle mass (SMM) and mean reaction time on go trial (standardized B = -0.28; p = 0.02). Multivariate analysis of covariance (MANCOVA) revealed that underweight participants presented inferior working memory compared to their normal weight (p = 0.001) or overweight peers (p = 0.008). However, according to the percentage fat quartiles (Q) participants with the highest quartile (Q4) were inferior in inhibitory control than their peers with Q2 (p = 0.04), and participants with the lowest quartile (Q1) were inferior in working memory compared with their peers with Q2 (p = 0.01) or Q3 (p = 0.02). A worse inhibitory control was observed for participants with the highest fat/SMM (Q4) compared to participants in Q3 (p = 0.03), and in contrast worse working memory was observed for participants with the lowest fat/SMM (Q1) compared to participants in Q2 (p = 0.04) or Q3 (p = 0.009). Conclusions: Low adiposity is associated with worse working memory, whereas high adiposity is associated with worse inhibitory control. Therefore, our findings show that normal adiposity, but greater SMM may have a positive impact on executive function in young adults.