Energy restriction (ER) has proven to be the only effective means of retarding aging in mice. The mechanisms of multiplicity of effects of ER on aging remain, however, fragmentary. ER induces daily torpor, the induction of which is reduced by increasing the ambient temperature to 30 degrees C. The effects of preventing hypothermia in ER animals were studied in terms of the expected consequences of ER on survival, disease pattern and a number of physiological parameters in autoimmune prone MRL/lpr mice and lymphoma prone C57BL, 6 mice. The results demonstrate that torpor plays a crucial role in the prevention of lymphoma development but does not have an affect on other aspects of ER, such as prevention of autoimmune diseases.