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 Recent research suggests that smell plays a large role in people’s
food intake, as the sense of smell is linked to the hunger center in
the brain, the researchers write in Chemical Senses.
“In an era of rising worldwide obesity, we still need to understand
more about the role of olfaction in eating behavior,” said lead
author Lorenzo Stafford, a senior lecturer at the Center for
Comparative and Evolutionary Psychology at the University of
Portsmouth in England.
Previous research has been conflicted over whether obese people have
a stronger or weaker sense of taste, but very few studies have
looked at the sense of smell, or olfaction, Stafford told Reuters
Health in an email.
The research team selected 40 university students for the study and
categorized them as either obese or non-obese. All the participants
were nonsmokers in good health who were not currently in weight loss
programs or taking appetite suppressants.
Underweight people as well as those with an impaired sense of smell
or taste were excluded.
First, the researchers asked students to smell an artificial dark
chocolate flavor and rate how intense it was and how pleasant they
found the smell. The flavor was then diluted into solutions of
different strengths and the participants were tested to determine
the lowest concentration they could reliably detect.
The researchers also tested the participants on their sense of taste
using the four main flavors: sour, salty, bitter, and sweet.
Solutions of each taste were sprayed onto the participants’ tongues
and they were asked to identify and rate the strength of each one.
The research team then analyzed the data to determine the
relationship between the senses of smell and taste and body weight.
They found that obese people were better at detecting the chocolate
odor than the non-obese group and also rated the odor as more
pleasant.
In addition, the obese participants perceived the salty taste as
more salty and the sour taste as more sour than non-obese people.
There was no difference between the groups for the bitter and sweet
tastes.
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The researchers write that smell is significant in eating behavior
because it triggers the reward center in the brain. Stafford noted
that sensory cues such as sight and smell can increase cravings for
addictive substances and theorizes that the same may be true for
foods.
He said that the smell of high-calorie foods “might also trigger
craving and possibly lead to overconsumption for those individuals
prone to weight gain.”
Lucy Donaldson at the University of Nottingham said that while the
results seem to show a preference for sweet foods, this could also
apply to sweet but low-calorie foods such as fruit. She said more
testing is needed to narrow the results.
Donaldson, who was not involved in the study, also noted in an
email, “the factors that contribute to eating behavior and obesity
are more complex and complicated than just taste or smell perception
alone.”
She added that it is difficult to know if the differences in smell
perception are part of what causes obesity or if these differences
are caused by obesity.
She recommends that for anyone looking to maintain healthy eating
habits, “eating a varied and balanced diet is the healthiest
option.”
SOURCE: bit.ly/1bPBSuf Chemical Senses, online March 13, 2015.
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