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Diet isn’t necessarily as innocent as it seems. The research is iffy…but it’s definitely not good.
Recently, I cut all added sugar from my diet for an entire week. For my experiment, I also banned artificial sweeteners. Why? Well, first of all, it felt like a cop out. But mostly, it’s because emerging research suggests the fake stuff can have some of the same drawbacks as real sugar—like being not so great for our waistlines.
Diet drinks, sweetened with artificial sweeteners like aspartame and sucralose, are either very low calorie or calorie free. Recent studies have suggested that they may still encourage weight gain. The relationship is complicated, though, and pretty controversial.
“The epidemiological studies looking at the association between people who consume diet soda and weight and those who don’t consume it typically show that consuming is associated with higher rates of obesity and higher rates of other metabolic complications,” Allison Sylvetsky Meni, Ph.D., assistant professor at the Milken Institute School of Public Health at The George Washington University, tells SELF. The problem is that these results come largely from observational studies and may suffer from a bias called reverse causation, Vasanti Malik, a research scientist in the department of nutrition at Harvard T.H. Chan School of Public Health, tells SELF. Reverse causation basically means that it’s difficult to know if x caused y or if y actually caused x. “When looking at diet soda it’s a real issue. People who drink diet soda may already be overweight or have a [metabolic] disease,” Malik explains. When you consider that relationship, you have to be skeptical of the association.
Malik also notes that compared to drinking regular sodas and other sugary drinks, diet options seem to be better. “When we looked at this at Harvard, we found that diet soda was associated with less weight gain compared to regular soda,” she says. She also references two randomized, controlled trials that showed less weight gain drinking diet vs regular. “Really, the evidence is pointing to benefit of diet consumption and weight maintenance at least in the short term.” There is some evidence that diet soda drinkers have a similar type 2 diabetes risk to regular soda drinkers, Meni says. “It could just be the idea of reverse causality, and that those people are already at risk,” she adds. But it’s likely a combo of that and some other mechanism.
Though both experts agree the evidence is sparse and more research is needed (and in progress), they cite a few viable scientific explanations for the connection between diet soda and weight gain. Here are the most promising four.