 Smelling food undermines dietary restriction in nematodes. Experiments by researchers have shown that the smell of food is enough to reduce the lifespan gains caused by dietary restriction in nematodes, and the same might hold true in mammals. Researchers grew C. elegans nematodes in Petri dishes with and without bacteria, which is what they eat. Some of the plates had a thin layer of bacteria on the lids, the nematodes could smell them but could not eat them. This had no effect on the lifespan for the nematodes with free access to bacteria, but in the dishes without bacteria it caused a 50% decrease in the longevity gain from dietary restriction. In a nutshell, the smell of bacteria offset some of the lifespan extension caused by dietary restriction. The team also pieced together the neural circuit involved. The signal is carried through a sequence of neurons from the brain to the intestine. Interfering with any of the neurons in the link blocked the effect of the food smell. See the full video at youtube.com backslash x10 show