Measurement of 24 h energy expenditure in male tuberculosis patients.

Background & Objectives: The total daily energy expenditure in patients with infectious disease is presumed to be high because of an increase in the basal metabolic rate (BMR), a reason for the weight loss observed in these patients. A reduction in daily physical activity, which may reduce the total daily energy expenditure. The aim of this study was to measure the free living total daily energy expenditure and physical activity of newly diagnosed hospitalized patients with tuberculosis using the labelled bicarbonate method.
Methods: In 6 healthy volunteers and 6 patients with newly diagnosed tuberculosis, 13C labelled bicarbonate method was used to measure free living total daily energy expenditure and physical activity. The 13C sodium bicarbonate (NaH13CO3) tracer was infused intravenously over a 48 h period and breath samples collected at regular intervals to estimate expired 13CO2.
Results: The patients had a 14 per cent increase in their BMR although they were not febrile at the time of measurement. However, their total daily energy expenditure was lower than that of the controls (mean value of 8.3 and 10.3 mJ/day respectively) and their physical activity level was also lower (mean 1.4 and 1.6 units respectively).
Interpretation & Conclusion: The total daily energy expenditure of afebrile patients with newly diagnosed tuberculosis is not higher than that of sedentary controls, despite an increased basal metabolic rate. It is possible that the observed weight loss in patients with tuberculosis is due to a reduced energy intake linked to anorexia associated with the disease. These findings may have relevance in nutritional treatment of chronic infections.