Behavior: Nose Knows More Ways Than One

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Smell spells love, hunger and higher heartbeats

Enough of Atkins, Stillman and Scarsdale. It may be that the Boring Diet works as well—or better. Scientists have long reasoned that if good taste and smell can increase appetite, terrible taste and odor, or one flavor eaten over and over, should be boring enough to decrease it. Last week, at an international conference on "The Determination of Behavior by Chemical Stimuli," a pair of biologists reported findings suggesting that any tedious diet helps weight loss. If it were possible to eat one food all the time, according to Israeli Nutritional Biochemist Michael Nairn, all but the genetically obese would quickly shed pounds.

At Jerusalem's Hebrew University, Nairn and French Neurobiologist Jacques Le Magnen spoke to a gathering sponsored by the European Chemoreception Research Organization, joining some two dozen other scholars who reported on such topics as the sniffing power of infants, the sex life of guinea pigs and a three-nation T shirt-smelling study.

Le Magnen's work shows that when their diet is monotonous, rats eat only what they need, but overeat and become fat when fed a different flavor every 30 minutes. At the conference, he reported that the taste and smell of the food encouraged hunger and obesity by causing a reflexive increase in insulin. Le Magnen also reported evidence, in both rats and humans, that each new tasty food produces a conditioned insulin release. In other words, even if a varied meal and a one-food meal are equal in size and good taste, the varied meal may prove more fattening because it increases appetite. According to Nairn, the best way for humans to lose weight may be to adopt a varied and revolting diet: food that is too sweet one day, too salty the next, or alternately bitter and sour.

Hebrew University Physiologist Jacob Steiner told the scientists that all tastes and smells accelerate the heart rates of adolescents. A sweet taste speeds the heart by 2% or 3%, bitter and sour tastes race the pulse 17% to 20% faster. Steiner, in long-term test studies of infants, discovered that first reactions to smells are inborn, not acquired. Newborns react positively to pleasant odors and screw up their faces in response to unpleasant ones, even before they have tasted any food at all.

Psychobiologist Gary Beauchamp of Philadelphia reported that the odor of female guinea pig urine is such a powerful stimulus to the male that it loses interest in mating if its sense of smell is impaired. When Beauchamp removed the male's vomeronasal organ, which relays odor information to the brain, sexual activity declined. In the wild, after the removal of the vomeronasal organ, even guinea pigs near their mates sometimes cannot find them.