Association of daily-life functioning and obesity in individuals with schizophrenia and controls

Early weight gain following the diagnosis of schizophrenia (SCZ) has been associated with improved daily functioning. However, in the general population and in other psychiatric conditions such as bipolar disorder, increased body mass index (BMI) has been associated with worse functioning. The data on this association in chronic individuals with SCZ is still scarce. To address this gap in knowledge, our objective was to evaluate the association between BMI and psychosocial functioning in chronic outpatients with SCZ and in healthy individuals. Six-hundred individuals (n = 600), 312 with schizophrenia (SCZ) and 288 individuals with no personal or family history of severe mental illness (CTR), underwent weight, height and psychosocial functioning score (FAST) assessment. Linear regression models tested the association between FAST as dependent variable and BMI as independent variable, controlling for age, sex, use of clozapine and years of illness. In the CTR group, the highest BMI could predict a worse result in FAST, explaining about 22% of the variation found (Model: AdjR² = 0.225 F_(3,284) = 28.79 p < .001; BMI main effect: β = 0.509 t = 9.240 p < .001). In the SCZ group, there was no statistically significant association. Our findings corroborate the perception that increased BMI is associated with worse functioning status in the general population. In chronic SCZ, whatsoever, there is no association. Our findings suggest that patients with higher BMI in the SCZ group may compensate for the possible impairment of functionality due to increased body weight, through improved adherence and responsiveness to prescribed psychopharmacological treatment, leading to better control of psychiatric symptoms.