Thursday, January 15, 2009
Are diet soft drinks bad for you? I received this question from Perry Romanowski after it came up on his blog, Just Your Average Joggler (which I highly recommend) and I thought it would make an excellent topic for today. More specifically, I would like to discuss the relationship between diet soft drinks and obesity.
At first, I did not expect there to be any relationship between diet soft-drinks and obesity - if they contain no calories, they can't possibly contribute to a positive energy balance, right? (e.g. energy in > energy out). Early studies of calorie-free sweeteners like aspartame seem to support that position. For example, a review article from 1991 suggests that "aspartame-sweetened foods or drinks is [sic] associated with either no change or a reduction
in food intake". However, more recent studies suggest that the issue is not quite so simple.
An article published last summer by Sharon Fowler in the journal Obesity suggests that individuals who consume diet soft drinks are at dramatically increased risk of overweight and obesity than those who do not consume diet soft drinks. For example, over an 8-year period, individuals who consumed just 3 diet soft drinks a week were 40% more likely to be overweight or obese than those who consumed none. The risk of overweight and obesity continued to increase dramatically with increased diet soft drink intake, and was independent of other factors like exercise, smoking, and socioeconomic status.
The Fowler study doesn't prove that diet soft drinks cause obesity (people who drink more diet soft drinks may also have other behaviors that put them at increased risk for weight gain), but they are still pretty surprising. While diet soft drinks may themselves be free of calories, recent evidence suggests that they may increase caloric intake at future meals. For example, when rats are given access to unlimited amounts of food, those who are used to consuming calorie-free drinks eat dramatically more than those who are used to consuming drinks flavoured with sucrose. It may be that calorie-free drinks impair the body's ability to anticipate the caloric content of a given meal, eventually resulting in increased caloric intake and weight gain. Others have suggested that calorie-free sweeteners like aspartame may also increase appetite at future meals.
So, while it is not yet completely clear if diet soft drinks cause obesity, there are some good reasons to limit their intake. Plain water is always a great choice, and if you find that too boring, consider adding a few slices of lemon or cucumber to add some fresh flavour (an idea I had never heard of until I came across it on the Thought for Food blog). And as always, a little physical activity is always a good decision :)
Thanks again to Perry Romanowski for the interesting question.
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