Energy balance and brown fat activity in adrenalectomized male, female, and castrated male rats.

Adrenalectomy (ADX) attenuated body weight and energy gains in male and female rats by inhibiting food intake and reducing energetic efficiency, and these changes were associated with marked increases in the thermogenic activity of brown adipose tissue (BAT). Feeding a palatable cafeteria diet to intact female rats stimulated energy intake, expenditure, and BAT activity and caused only small increases in body energy gain. Heat production in cafeteria-fed female rats was further enhanced by ADX. Castration in male rats had similar effects on energy balance and BAT to adrenalectomy, causing decreases in energy intake, expenditure, body energy gain, and energetic efficiency, but elevated BAT activity. Combined castration and ADX had synergistic effects resulting in marked increases in brown fat activity. These data indicate that male steroids may inhibit thermogenesis in a similar manner to the glucocorticoids, but the effects of adrenalectomy on energy balance are comparable in male and female rats.