for National Geographic News
Flies on a diet live much longer than flies that are allowed to eat all they want. But just a small whiff of extra food is enough to shorten the lives of the dieting flies again, a new study shows.
The effect only occurred in flies on restricted rations, though.
When flies could eat their fill—and thus already had shortened lives—smelling more food didn't cut their lives any further.
The research, led by Scott Pletcher of the Baylor College of Medicine in Houston, Texas, confirms a strong connection between smell and life span.
The study will be published tomorrow in the journal Science.
Many animals—from monkeys to mice to microscopic worms—live longer when they eat less than their fill. (Related: "Discoveries May Help Unlock Secrets of Long Life" [October 30, 2003].)
The effect may occur because animals are genetically programmed with strategies for dealing with food shortages.
During famines, for instance, they could put more of their energy into repairing their bodies and living longer.
But when a cornucopia of food abounds, the animals put their energy into making babies.
At normal food levels, for example, flies live about 45 days. When they can eat as much as they want, the flies only last about 35 days. But when they're on the optimal diet, they live about 55 days—about 60 percent longer.
The smell of food erased about a quarter of the gain they got from dieting, though.
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