If that can of diet cola in the late
afternoon spares you a few hundred calories that you
would have gotten from a chocolate bar, it looks like
you've come out ahead. But have you? Maybe not, say
researchers from Purdue University. Sure, you saved
some calories, but you might be throwing your body's
ability to regulate calorie intake out of whack --
and that could be the downfall of your diet in the long run.
It seems that human beings may have
learned -- or be programmed to use -- food properties,
such as sweetness, to predict the caloric content of the
foods they eat, says Terry L. Davidson, PhD, professor,
department of psychological sciences at Purdue and coauthor
of a recent study on sweetener use. When we eat "real foods,"
that ability helps us to quit eating before we've consumed
more calories than we need. Products that use artificial
sweeteners do not seem to trigger this mechanism.
But if you regularly consume
calorie-free sweet drinks, such as diet sodas,
you might be less able to control your appetite later on.
In Dr. Davidson's study, rats that
were given a calorie-free, saccharin-sweetened drink
for 10 days had a harder time controlling their
appetites when exposed to a treat than rats fed a
high-calorie sweet drink. "It seems possible that
tastes and viscosity help animals and people
anticipate the number of calories that are contained
in a meal -- a kind of early warning for the gastrointestinal
tract," Dr. Davidson told me.
If you're thinking that makes it better
to grab a regular soda instead -- you are wrong. A thin
(low-viscosity), high-calorie beverage, such as juice,
fruit drinks, "ades" and regular sodas, also may foil
appetite control, says Dr. Davidson, who found in a second
study that rats that ate a snack with a consistency similar
to pudding were better able to regulate their calorie intake
than rats that ate a snack with a consistency similar to milk,
even though both snacks contained the same number of calories.
Interestingly, the consumption of artificially
sweetened drinks has increased during the same period that more
and more Americans have become overweight or obese. While the
obesity epidemic has a number of causes, the increased use of
sweeteners may be contributing factors, Dr. Davidson says.
Of course, the jury is out in general on
the safety of most artificial sweeteners (See Daily Health
News, December 8, 2003). Even if you haven't made up your
mind on that issue, Dr. Davidson's research does make you
wonder about whether that diet drink might be sabotaging
your weight-control efforts in the long run.
Terry L. Davidson, PhD, professor,
department of psychological sciences, Ingestive Behavior
Research Center, Purdue University, West Lafayette, Indiana.
