Study: Artificial Sweetener May Disrupt Body's Ability to Count Calories

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Study: Artificial Sweetener May Disrupt Body's Ability

to Count Calories

Provided by AScribe Newswire on 7/6/2004

by Purdue University

 

WEST LAFAYETTE, Ind., June 29 (AScribe Newswire) --

Choosing a diet soft drink over a regular,

sugar-packed beverage may not be the best way to fight

obesity, according to new research from Purdue

University. But the researchers said this doesn't mean

you should grab a regularly sweetened soft drink

instead.

 

Professor Terry Davidson and associate professor Susan

Swithers, both in the Department of Psychological

Sciences, found that artificial sweeteners may disrupt

the body's natural ability to " count " calories based

on foods' sweetness. This finding may explain why

increasing numbers of people in the United States lack

the natural ability to regulate food intake and body

weight. The researchers also found that thick liquids

aren't as satisfying - calorie for calorie - as are

more solid foods.

 

Based on the research, Davidson and Swithers suggest

paying more attention to calories consumed and

engaging in regular exercise to battle the bulge.

 

The Purdue's researchers' study, " A Pavlovian Approach

to the Problem of Obesity, " appears in the July issue

of International Journal of Obesity. Davidson and

Swithers, members of the Ingestive Behavior Research

Center at Purdue, suggest that being able to

automatically match caloric intake with caloric need

depends on the body's ability to learn that the taste

and feel of food by the mouth suggests the appropriate

caloric intake. Much as Pavlov's dogs learned that the

sound of a bell signaled food, people learn that both

sweet tastes and dense, viscous foods signal high

calories. This learning process begins very early in

life and perhaps without conscious awareness,

according to the researchers.

 

" The body's natural ability to regulate food intake

and body weight may be weakened when this natural

relationship is impaired by artificial sweeteners, "

said Davidson, an expert in behavioral neuroscience.

" Without thinking about it, the body learns that it

can use food characteristics such as sweetness and

viscosity to gauge its caloric intake. The body may

use this information to determine how much food is

required to meet its caloric needs. "

 

Over the past 25 years, there has been a dramatic

increase in the consumption of artificially sweetened

foods and low viscosity, high-calorie beverages, said

Swithers, a developmental psychobiologist.

 

" Incidence of overweight and obesity has also

increased markedly during this period, " she said. " Our

hypothesis is that experience with these foods

interferes with the natural ability of the body to use

sweet taste and viscosity to gauge caloric content of

foods and beverages. When you substitute artificial

sweetener for real sugar, however, the body learns it

can no longer use its sense of taste to gauge

calories. So, the body may be fooled into thinking a

product sweetened with sugar has no calories and,

therefore, people overeat. "

 

Swithers said that the loss of the body's ability to

gauge caloric intake contributes to increased food

intake and weight gain, especially when people do not

count calories on their own. A similar dynamic is at

work with foods' texture and thickness.

 

" Historically, we knew that our body learns that if

the food is thick, such as whole milk, it tends to

have more calories than compared to a thinner liquid

such as skim milk, " Swithers said. " Now, our research

reinforces this and takes it one step further, showing

that our bodies translate this information about

perceived calories into a gauge to tell us when to

stop eating. "

 

The researchers based their hypothesis on Pavlovian

theory. Ivan Pavlov, known for his work in the early

20th century, is famous for his experiment in training

dogs to associate food with the ringing of a bell.

After being conditioned to the bell, the dogs

salivated when they heard it - even when they did not

see or smell food. Davidson and Swithers propose that

rats learn a similar relationship between the taste or

texture of a food and the calories it contains and may

use this information to control food intake and body

weight.

 

Davidson and Swithers' findings are based on two

studies.

 

In the first study, two groups of rats were given two

different sweet-flavored liquids. In the first group,

both liquids were sweetened with natural high-calorie

sweeteners so there was a consistent relationship

between sweet taste and calories. For the second

group, one of the flavored liquids was artificially

sweetened with non-caloric saccharin so that the

relationship between sweet taste and calories was

inconsistent.

 

After 10 days of exposure to the flavors, the rats

were allowed to eat a small amount of a sweet,

high-calorie chocolate flavored snack. The researchers

compared the two groups' ability to compensate for the

calories contained in the chocolate snack. The rats

that had experienced the inconsistent relationship

between sweet taste and calories were less able to

compensate for the calories contained in the snack and

ate more than the rats that had experienced the

consistent relationship between sweetness and caloric

intake.

 

" This suggests that experience with the inconsistent

relationship reduced the natural ability of the rats

to use sweet taste to judge the caloric content of the

snack, " Swithers said.

 

In the second study, two groups of rats were given a

high-calorie dietary supplement along with their

regular food every day for 30 days. Although the

supplements were identical in calories and nutritive

content, they differed in viscosity. For one group the

supplement had the consistency of thick chocolate

pudding, whereas for the other group, the supplement

was similar to chocolate milk. Davidson and Swithers

found that over the course of the study, the rats

given the milk-like supplement gained significantly

more weight than the rats given the more viscous,

pudding-like supplement.

 

" This finding indicates that rats are less able to

estimate and compensate for the calories contained in

liquids than in semi-solid foods, " Davidson said. " If

the body is less able to detect and compensate for

calories contained in liquids, then intake of

high-calorie beverages compared to semi-solid or solid

foods could increase the tendency to gain weight. "

 

The number of Americans consuming sugar-free products

increased from less than 70 million in 1987 to more

than 160 million in 2000. During the same period, the

consumption of regular soft drinks increased by more

than 15 gallons per capita annually.

 

" Increased consumption of artificial sweeteners and of

high-calorie beverages is not the sole cause of

obesity, but it may be a contributing factor, "

Swithers said. " It could become more of a factor as

more people turn to artificial sweeteners as a means

of weight control and, at the same time, others

consume more high-calorie beverages to satisfy their

cravings. "

 

Davidson and Swithers are evaluating potential

mechanisms that may produce the short- and long-term

effects on food intake and body weight, as well as

whether age or gender are contributing factors.

Additional research also will need to evaluate if the

body and brain can be retrained to naturally measure

calories after consuming artificial sweeteners or

high-calorie beverages.

 

The National Institute of Child Health and

Development, National Institute of Digestive Diseases

and Kidney Disorders, and Purdue School of Liberal

Arts funded this research.

 

CONTACTS:

 

Writer: Amy Patterson-Neubert, 765-494-9723,

apatterson

 

Source: Susan Swithers, 765-494-6279, 317-345-5828,

swithers

 

RELATED WEB SITES:

 

Purdue Psychological Sciences:

http://www.psych.purdue.edu/

 

Ingestive Behavior Research Center:

http://www.psych.purdue.edu/~ibrc/index.html

 

The Calorie Control Council:

http://www.caloriecontrol.org/

 

NOTE TO EDITORS: Broadcast-quality audio clips are

available at

http://news.uns.purdue.edu/UNS/html4ever/040629.Swithers.research.html.

B-roll footage of Susan Swithers in her lab is

available by contacting Amy Patterson-Neubert,

765-494-9723, apatterson.

 

PHOTO: A publication-quality photograph of Terry

Davidson and Susan Swithers is available at

http://ftp.purdue.edu/pub/uns/+2004/swithers-davidson.jpg.

 

PHOTO CAPTION: Susan Swithers, associate professor of

psychological sciences, and Terry Davidson, professor

of psychological sciences, studied how artificial

sweeteners disrupt the body's ability to naturally

count calories. Based on the research, Davidson and

Swithers suggest that switching to a diet drink may

not be the best solution to fight obesity. Their

study, " A Pavlovian Approach to the Problem of

Obesity, " appears in this month's International

Journal of Obesity. Both researchers are members of

the Ingestive Research Center at Purdue. (Purdue News

Service photo/David Umberger)

 

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