Investigation of Alexithymia and related psychological factors in relation to body mass index and obesity

Common obesity is thought to be the result of genetic variations influencing susceptibility to environmental circumstances related to food intake, mediated by appetite-regulating pathways, and also affected by emotional processing and other behavioural traits. Alexithymia is a psychological construct for emotional processing deficits, characterised by impaired identification and description of feelings, and externally-oriented thinking. Here, I investigate the relationship between alexithymia, measured by the 20-item Toronto Alexithymia scale (TAS-20), and adiposity in two Northern Finland Birth Cohorts (NFBC1966 and NFBC1986) and in severely-obese adults seeking bariatric surgery in the UK (PMMO clinical trial). Analysis of depression as a possible contributing factor in the relationship between alexithymia and obesity was also conducted in the NFBC1966. Consistent associations between BMI and TAS-20 total scores were observed among adult and adolescent general populations and in severely-obese adults (pre- and post-surgery, assessed longitudinally). Males with clinically-relevant alexithymia status (TAS-20≥ 61) and history of depression diagnosis had higher BMI than males without, at age of 31 years in NFBC1966. In the severe obesity clinical trial cohort (PMMO), participants with history of clinical depression diagnosis had higher TAS-20 total scores and weight at baseline than those who had no clinical depression history. Depression and bariatric surgery type were also moderately associated with TAS-20 total scores after surgery. A genome-wide association study was conducted to identify genetic variants influencing psychological measures (TAS-20 and HSCL-13 scores) in the general adult and adolescent populations. In the NFBC1966 dataset, one SNP, rs2242223 (p= 8.10 x 10-8) in the Parkinson’s disease gene SNCAIP (synuclein alpha interacting protein) was associated with TAS-20 score. There were also significant sex and genotype interactions. These findings raise intriguing questions regarding the direction of causal mechanisms between emotional processing and obesity. Design of treatment strategies for complex conditions, such as obesity, would benefit from enhanced understanding of underlying psychological/behavioural components in the general population and clinical patients.Open Acces