Every now and then, a new study turns up warning consumers that diet soda is too good to be true. (Although it seems to us that an occasional reminder that drinking zero-calorie colas doesn t negate other calories is probably all the public needs.) Another one of these so-called studies washed up at the American Diabetes Association s Scientific Sessions in San Diego. There, researchers from the School of Medicine at the University of Texas Health Science Center, San Antonio, reported that the regular consumption of diet soft drinks was linked to an increased waist circumference. The findings from a group of 474 people are that, over an average of 9.5 years, diet soda drinkers expanded their waistlines by 70 percent more than those who did not drink diet soda. What s more, those who consumed two or more diet sodas a day saw their waist circumference increase by 500 percent more than non-users.
This is nothing but junk, says ACSH's Dr. Elizabeth Whelan. ACSH advisor and epidemiologist Dr. Geoffrey Kabat agrees. Those who gained weight and those who didn t probably differ on many variables that would have an effect on weight gain, he notes. The authors have a preconceived (but unjustified) premise that just because their subjects both gained weight and consumed diet soda, one must be the cause of the other but they got it backwards. In other words, diet soda drinkers are often already overweight, so it s not surprising that their waists expand more significantly when compared with those who feel no need to drink diet soda in the first place. Indeed, the problem with such fairly loose studies is their failure to address the number of factors involved that could confound the association between drinking diet soda and whatever health problems are being claimed. It is, ultimately, more beneficial to remember that diet soda is not a panacea or a license to eat more, but only a means of reducing the number of calories that are in a glass of soda.
ACSH's Dr. Josh Bloom comments that the biological premise of this study is preposterous. He points out that the diet sodas were not even categorized by which artificial sweetener was used. It is unlikely enough that any one of the artificial sweeteners could activate some unknown mechanism that just happens to lead to weight gain," he says. "But for multiple, chemically unrelated sweeteners to all behave in the same manner is just plain ridiculous. Biochemistry just doesn t work that way.