Turns out all the news stories and blog postings cite the same few studies: research in rats conducted by two investigators at Purdue University and two studies that followed soda drinkers over time.
Popkin, who heads the division of nutrition epidemiology at the University of North Carolina, Chapel Hill, says none of the studies makes a convincing case that no-calorie sodas contribute to weight gain.
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“The bloggers of the world have latched on to the notion that diet sodas cause obesity, but the science just isn’t there to back it up,” Popkin says.
In an analysis published last year, Popkin and co-author Richard D. Mattes, PhD, MPH, RD, who is a nutrition professor at Purdue University but was not involved in the rat studies, reviewed the research examining the impact of artificial sweeteners on weight.
They found little support for the notion that no-calorie sweeteners stimulate appetite or contribute to obesity in some other way, but they say more research is needed to know for sure.
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It may also be that people with very poor diets disproportionately drink diet sodas.
Popkin calls this the “Big Mac and Diet Coke” mentality.
“Especially in America, we have a lot of people who eat high-fat, high-sugar diets, but also drink diet sodas,” he says.