Measured and expected resting energy expenditure in patients with bipolar disorder on maintenance treatment

Patients with bipolar disorder (BD) on long-term maintenance treatment represent a clinical population with peculiar characteristics, for which available equations to estimate resting energy expenditure (REE) are not suitable. The aim of this study was to measure REE by means of indirect calorimetry in bipolar patients on maintenance treatment and in controls, and to estimate the agreement between measured and predicted REE in both groups.

Patients diagnosed with BD I and healthy controls were assessed for height, weight and body mass index (BMI). Predicted REE was calculated using Harris-Benedict, Schofield, Recommended Nutrients Assumption Levels (LARN), and OUR equations; measurements of REE were performed using a portable indirect calorimeter.

Results for our sample show the most commonly used formulas give a systematic overestimation of REE with respect to measured basal metabolic rate in the patient group. The mean bias was considerably greater for bipolar subjects than for controls.

These results suggest that patients with severe mental illness on long-term psychopharmacologic treatment may have reduced basal energy expenditure that may be a cause of weight gain.