Should There Be a Diet Soda Tax?

Sugary drinks are often cited as big evildoers in the obesity epidemic. Many recent studies have shown that our consumption of sugary drinks may be related to an increasing national mass, and various taxes on these beverages are being considered all over the nation. 

But is a soda tax totally useless in the fight against obesity? And should there actually be a diet soda tax?

A new Northwestern University study, which concluded that obese people tend to drink diet soda way more than regular soda, indicates that taxing regular sodas and other sweetened drinks would be an ineffective way to combat obesity. The proposed taxes exclude artificially-sweetened diet sodas.

Researcher Ketan Patel, who worked on the Northwestern study, says, “My research suggests that a soda tax would not be effective in reducing weight for people that are already obese because obese people have a strong preference for diet soda.”

Oh, the irony: New studies show that diet soda may cause people to gain weight rather than lose it.

How can consuming something with low caloric numbers like diet soft drinks make you fat?

According to the San Antonio Longitudinal Study of Aging (SALSA)—a 10-year study involving 474 participants—diet soda drinkers had 70 percent greater increases in waist circumference than non-users. Those who consumed two or more diet sodas a day ended up with waist increases that were five times greater than those of non-diet-soda drinkers.

Holy Coke Zero!

“Emerging research suggests that those who regularly consume diet soda may be more at risk for weight gain and subsequently, becoming overweight or obese compared with those who don’t drink it,” says Elisa Zied, M.S., R.D., C.D.N., registered dietitian and author of “Nutrition At Your Fingertips.”

As the SALSA researchers, from the University of Texas Health Science Center at San Antonio, wrote in their abstract: “Diet sodas… may be free of calories, but not of consequences.” 

DISCUSS: Will the new diet soda research make you stop drinking it?

Results of the SALSA study, announced last week at a meeting of the American Diabetes Association in San Diego, haven’t yet been published or peer-reviewed, and there are varying theories as to their cause. One is that fake-sugary drinks may be extra-bad for you because when you taste something sweet, your metabolism revs up to burn calories, but if that sweetness comes with zero calories (like with diet sodas), the metabolism’s instinct to speed up breaks down and, over time, you gain weight. This hypothesis has been supported by studies involving saccharin and rats.

THE STUDY, EXPLAINED: Fake Sugars Cause Weight Gain

Another theory is that heavy people may simply consume more diet drinks and think that they’re not taking in as many calories as they really are. Richard Mattes, a nutrition scientist at Purdue University, has studied artificial sweeteners’ affect on appetite and food intake, and he believes that diet soda drinkers reason that they can eat more calories because they’re choosing the zero-calorie beverage. Call this the “large buttered popcorn and a small diet soda, please” phenomenon.

A tax on full-sugar beverages may drive more consumers to untaxed artificially sweetened drinks, so it’s especially important to explore the potentially unhealthy effects of these diet drinks with studies like the SALSA.

MORE: Sweeteners Guide 

Want the short answer? The next time you’re considering your beverage options, treat the sugary drinks as a rare treat, and don’t be tempted by the zero-calorie status of artificially sugared choices. Grab a seltzer if you need carbonation. In other words, and you’ve heard it before: Drink more water.