The effect of prohibiting outside food during COVID-19 pandemic on the body weight of schizophrenic patients taking olanzapine or clozapine: a retrospective self-controlled study

Background: Olanzapine and clozapine are atypical antipsychotics (AAPs) with the greatest risk of weight gain, and changes in feeding behavior are among the most important underlying mechanisms. However, few studies have investigated the role of diet-alone interventions in improving individuals' weight gain by taking AAPs. In closed management mental hospitals of China, family members are allowed to bring food to patients regularly, causing patients to have caloric intake added to their 3 daily meals. However, during the global pandemic of coronavirus disease 2019 (COVID-19), bringing food to the hospital was temporarily prohibited in mental health institutions in China to prevent the spread of the virus. This study sought to compare the body weight and body mass index (BMI) changes of patients taking olanzapine or clozapine undergoing diet-alone interventions caused by this prohibition. Methods: A retrospective self-controlled study was conducted on 90 patients with schizophrenia from a single-center treated with olanzapine or clozapine monotherapy, or combined with aripiprazole or ziprasidone which has a small metabolic impact. A paired-samples t-test was used to compare the changes in body weight and BMI before and after the 3-month prohibition, and general linear regression was used to analyze the effects of gender, age, disease course, duration of drug exposure, and equivalent dose on the BMI improvement. Also, the percentage of people who lost weight and that of individuals who lost 5% of their pre-prohibition body weight were calculated. Results: Paired-samples t-test showed that after 3-month prohibition, the patients' body weight (71.68 +/- 6.83 vs. 66.91 +/- 7.03, P<0.001) and BMI (26.43 +/- 2.11 vs. 24.63 +/- 1.81, P<0.001) decreased significantly. Weight loss rate accounted for 99.1%, and weight loss of 5% from the pre-prohibition body weight accounted for 71.8%. General linear regression showed that the duration of drug exposure (beta=-0.678, P<0.001) was significantly and negatively correlated with the BMI changes. No significant correlation of gender, age, disease course, or equivalent dose with BMI changes was found. Conclusions: Diet-alone interventions facilitate weight loss in chronically hospitalized schizophrenia patients taking AAPs. Conduction of dietary intervention in the early stages of medication may yield greater benefits.