Cutting the connection
between sweets and calories may confuse the body, making it harder to regulate
Sweeteners Linked to Weight Gain
to lose weight?
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).
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.
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.
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.
people may have different experiences with artificial and natural sweeteners,
human studies that don't take into account prior consumption may produce a variety
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.
experimenters also measured changes in core body temperature, a physiological
assessment. Normally when we prepare to eat, the metabolic engine revs up.
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.
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.
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
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
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.
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.
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.
text of the article is available from the APA Public Affairs Office and at http://www.apa.org/journals/releases/bne-feb08-swithers.pdf
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