The resting metabolic rate of people with severe mental illness: A systematic review and meta-analysis.

People with severe mental illness (SMI), including schizophrenia and related psychoses and bipolar disorder, are at greater risk for obesity compared to people without mental illness. An altered resting metabolic rate (RMR) may be a key driving factor; however published studies have not been systematically reviewed. This systematic review and meta-analysis aimed to determine whether the RMR of people with SMI assessed by indirect calorimetry differs from (i) controls, (ii) predictive equations, and (iii) after administration of antipsychotic medications. Five databases were searched from database inception to March 2022. Thirteen studies providing 19 relevant datasets were included. Study quality was mixed (62% considered low quality). In the primary analysis, RMR in people with SMI did not differ from matched controls (N = 2, SMD = 0.58, 95% CI -1.01 to 2.16, p = 0.48, I 2 = 92%). Most predictive equations overestimated RMR. The Mifflin St. Jeor equation appeared to be most accurate (N = 5, SMD = -0.29, 95% CI -0.73 to 0.14, p = 0.19, I 2 = 85%). There were no significant changes in RMR after antipsychotic administration (N = 4, SMD = 0.17, 95% CI -0.21 to 0.55, p = 0.38, I 2 = 0%). There is little evidence to suggest there is a difference in RMR between people with SMI and people without when matched for age, sex, BMI and body mass, or that commencement of antipsychotic medication alters RMR.