THE EFFECT OF PHARMACOLOGICAL DOSAGES OF GLUCOCORTICOIDS ON FREE-LIVING TOTAL-ENERGY EXPENDITURE IN MAN

OBJECTIVES Weight gain had previously been thought to be due to increa sed calorie intake alone though no information on its effect on total energy expenditure is available in humans. We therefore assessed wheth er weight gain associated with glucocorticoids is due to a reduction i n energy expenditure. DESIGN We performed an open study with 1 mg of b etamethasone given orally twice a day for 21 days. SUBJECTS Seven heal thy female volunteers, age range 26-55 years, body mass index 19 to 40 , mean 27 kg/m(2). MEASUREMENTS Total free living energy expenditure w as measured by the doubly labelled water method (D-2 O-18), resting me tabolic rate by ventilated hood indirect calorimetry and fat free mass from the dilution volume of oxygen-18 labelled water. Body compositio n and components of energy expenditure were assessed before and during the final 14 days of betamethasone administration. RESULTS Weight inc reased by a mean of 1.2 kg (P < 0.05) because of a significant rise in fat mass (1.5 kg) with no change in fat free mass. Resting metabolic rate remained unaltered on betamethasone but total energy expenditure increased in all subjects with a significant mean rise of 26% from 11. 7 to 14.7 MJ/24 h (P < 0.05). The energy component of physical activit y with thermogenesis increased on average 52% (from 5.8 to 8.9 MJ/24 h ; P < 0.05). The rise in energy expenditure was still apparent after c orrection for the increase in body weight. Fasting respiratory quotien t (RQ) increased from 0.81 to 0.86 with no change in fasting blood glu cose. Betamethasone did not result in an energy sparing effect on the two components of energy expenditure studied. CONCLUSIONS Body weight increased on betamethasone entirely due to an increase in fat mass. Th is occurred despite a rise in total energy expenditure which involved specifically that component accounted for by physical activity plus th ermogenesis. The most likely explanation is that betamethasone increas ed dietary energy intake significantly in excess of expenditure. We es timate that an average extra energy intake of 2.8 MJ/day would have ha d to be consumed for this rise in fat mass to occur even before taking into account the energy intake cost of the rise in expenditure.