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Artificial
Sweeteners linked to weight gain
Newswise — Want to lose weight? It might
help to pour that diet soda down the drain.
Researchers have laboratory evidence that
the widespread use of no-calorie sweeteners
may actually make it harder for people to
control their intake and body weight.
The findings appear in the February issue of Behavioral
Neuroscience, which is published by the
American Psychological Association (APA).
Psychologists at Purdue University’s
Ingestive Behavior Research Center reported
that relative to rats that ate yogurt
sweetened with glucose (a simple sugar with
15 calories/teaspoon, the same as table
sugar), rats given yogurt sweetened with
zero-calorie saccharin later consumed more
calories, gained more weight, put on more
body fat, and didn’t make up for it by
cutting back later, all at levels of
statistical significance.
Authors Susan Swithers, PhD, and Terry
Davidson, PhD, surmised that by breaking the
connection between a sweet sensation and
high-calorie food, the use of saccharin
changes the body’s ability to regulate
intake.
That
change depends on experience. Problems with
self-regulation might explain in part why
obesity has risen in parallel with the use
of artificial sweeteners.
It also might explain why, says Swithers,
scientific consensus on human use of
artificial sweeteners is inconclusive, with
various studies finding evidence of weight
loss, weight gain or little effect.
Because people may have different
experiences with artificial and natural
sweeteners, human studies that don’t take
into account prior consumption may produce a
variety of outcomes.
Three different experiments explored whether
saccharin changed lab animals’ ability to
regulate their intake, using different
assessments – the most obvious being caloric
intake, weight gain, and compensating by
cutting back.
The experimenters also measured changes in
core body temperature, a physiological
assessment.
Normally when we prepare to eat, the
metabolic engine revs up. However, rats that
had been trained to respond using saccharin
(which broke the link between sweetness and
calories), relative to rats trained on
glucose, showed a smaller rise in core body
temperate after eating a novel,
sweet-tasting, high-calorie meal.
The authors think this blunted response both
led to overeating and made it harder to burn
off sweet-tasting calories.
“The data clearly indicate that consuming a
food sweetened with no-calorie saccharin can
lead to greater body-weight gain and
adiposity than would consuming the same food
sweetened with a higher-calorie sugar,” the
authors wrote.
The authors acknowledge that this outcome
may seem counterintuitive and might not come
as welcome news to human clinical
researchers and health-care practitioners,
who have long recommended low- or no-calorie
sweeteners.
What’s more, the data come from rats, not
humans. However, they noted that their
findings match emerging evidence that people
who drink more diet drinks are at higher
risk for obesity and metabolic syndrome, a
collection of medical problems such as
abdominal fat, high blood pressure and
insulin resistance that put people at risk
for heart disease and diabetes.
Why would a sugar substitute backfire?
Swithers and Davidson wrote that sweet foods
provide a “salient orosensory stimulus” that
strongly predicts someone is about to take
in a lot of calories. Ingestive and
digestive reflexes gear up for that intake
but when false sweetness isn’t followed by
lots of calories, the system gets confused.
Thus, people may eat more or expend less
energy than they otherwise would.
The good news, Swithers says, is that people
can still count calories to regulate intake
and body weight.
However,
she sympathizes with the dieter’s lament
that counting calories requires more
conscious effort than consuming low-calorie
foods.
Swithers adds that based on the lab’s
hypothesis, other artificial sweeteners such
as aspartame, sucralose and acesulfame K,
which also taste sweet but do not predict
the delivery of calories, could have similar
effects.
Finally, although the results are consistent
with the idea that humans would show similar
effects, human study is required for further
demonstration.
Article: “A Role for Sweet Taste: Calorie
Predictive Relations in Energy Regulation by
Rats,” Susan E. Swithers, PhD and Terry L.
Davidson, PhD, Purdue University; Behavioral
Neuroscience, Vol. 122, No. 1.
(Full text of the article is available from
the APA Public Affairs Office and at http://www.apa.org/journals/releases/bne-feb08-swithers.pdf )
The American Psychological Association (APA),
in Washington, DC, is the largest scientific
and professional organization representing
psychology in the United States and is the
world’s largest association of
psychologists. APA’s membership includes
more than 148,000 researchers, educators,
clinicians, consultants and students.
Through its divisions in 54 subfields of
psychology and affiliations with 60 state,
territorial and Canadian provincial
associations, APA works to advance
psychology as a science, as a profession and
as a means of promoting human welfare.
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