Diet Soda & Obesity
July 05, 2005
Diet sodas, which have no or very few calories, should
be a boon to the overweight
in their attempts to lose excess pounds. What, then,
can we make of a recent report about a study purportedly
showing that people who drink diet sodas, gain rather
than lose
weight. The answer might lie in the report, rather
than in biology, and is a great example of the drawbacks
of presenting preliminary reports (those which have
not been peer-reviewed) to the public.
The study in question was presented at a scientific
meeting of the American Diabetes Society by Sharon Fowler
from the University of Texas Health Science Center.
After following the body weights and dietary intake
of over 1500 individuals for seven to eight years, the
researchers looked at the relationship between the type
of soda the participants said they drank and their body
weight changes.
People who reported drinking half a can of regular
soda per day were 26% more likely to become overweight
or obese than those who drank none. The risk of gaining
weight increased even more -- to 47% -- for those who
drank over two cans per day.
Oddly, however, people who reported drinking diet soda
had an even greater risk of weight gain. The risk was
nearly 37% for half can per day consumers, and a whopping
57% for those who drank over two cans per day.
Could this really be happening? The truth may lie in
what the report failed to describe -- that is, what
changes the participants made in other aspects of their
lifestyles over the course of the study. Although switching
from a full-calorie soda to an equal amount of diet
soda will lower calorie intake, such a change is only
part of the story. At the same time, a person might
be increasing consumption of other foods or drinks,
thus negating any decrease in calories from sodas. Or
people might decrease physical activity and thus the
number of calories
used per day.
As reported, the story does quote a nutritionist who
points out the importance of looking at the whole diet
rather than just one component of it. But without appropriate
scientific support, it ends by speculating that sweet,
noncaloric diet drinks might make people actually want
to eat more. The report cites evidence that this can
occur in baby rats, but it's a far cry from young, growing
animals to adult humans -- human data would have made
this suggestion more convincing.
It's quite likely that there was much more to this
study than was reported in the online story -- such
as data on overall food intake and activity levels --
that would help the public make sense of evidence that
seems to contradict common sense. But if such data were
not presented, that fact should also have been part
of the report to let readers know that the whole story
was not presented at the meeting.
Unfortunately, reports like this dwell on the more
sensational, less likely aspects of research and don't
give enough context. It certainly should have indicated
that the presentation was preliminary in nature.
The most realistic assessment one can make of such
a report is that it's interesting, although contradictory
to well-established principles of weight gain and loss.
But it fails to give the consumer an appropriate context
in which to evaluate the study.
Source: http://www.wnep.com
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