Experiments show that moderate caloric restriction in normal (non-sterile) fruit flies results in the increase of life span. It has been found recently that life span increases under caloric restriction also in sterile Drosophila females. This fact was explained by remodeling of metabolism due to insulin signaling. In this paper a hypothesis is put forward that under caloric restriction in the organism, the energy arrival decreases so that the stationary state must be restored. To achieve this, reproduction is reducing, remodeling of metabolism and the increasing of substrates output from the gastrointestinal tract start. The increase of life span can be just a side effect of these processes. Simulation demonstrates that the experimentally observed life span increasing in non-sterile fly females under caloric restriction can be explained exclusively by the reducing reproduction.