Generation and compensation of the cancer cachectic process by spontaneous modification of feeding behavior.

Daily food intake and corresponding feeding activity (measured as duration) and feeding efficiency (amount of food ingested per unit of feeding activity) were measured both in normal Sprague-Dawley and Buffalo rats and during growth of Walker 256 and 4M mammary carcinomas in Sprague-Dawley rats and of Morris 5123 hepatoma in Buffalo rats. Estimates of meal size and frequency were also obtained. Growth of the carcinomas produced a decline in feeding activity accompanied, early in tumor growth, by a compensatory increase in feeding efficiency with no resultant effect on food intake. This compensated decline in feeding activity was due to reduction in average meal duration. Later, meal frequency was also reduced, with further reduction in feeding activity and reduction in food intake. There was little change in average meal size. The hepatoma produced a different detailed pattern of effect on feeding behavior. These effects are not nonspecific reactions to foreign tissue. The effects imply behavioral compensation for the breakdown of a rapidly responding physiological control of food intake and can be interpreted in terms of successive impairment of feeding control mechanisms that have different response rates and different behavioral modes.