Swapping Out Sugary Soda For Diet Drinks May Help Tip The Scale In Your Favor

Oct 22, 2012
Originally published on October 22, 2012 11:42 am

Diet soda. We love it or hate it. But there's no doubt that consumption is on the rise. More Americans than ever are drinking diet colas, along with other zero- and low-calorie alternatives.

While diet drink consumption is up across the entire population — about 1 in 5 of us consume them — it's higher-income, middle-aged women who are most likely to be sipping diet drinks, according to a recent Centers for Disease Control and Prevention survey.

As this increase happens, there's also evidence that Americans are drinking less sugar-sweetened soda. So the big question is, will swapping Coke for Diet Coke make any difference for people trying to manage their weight? Two recent studies suggest it just might.

Overweight adolescents who received home deliveries of water and zero-calorie drinks for one year did significantly better at limiting weight gain compared to a similar group of teens who continued drinking sugary beverages, according to a study by researchers at Boston Children's Hospital. (For more on the study, click on the audio button above to hear the radio piece.)

How much better? "We found there was a difference of just over four pounds," says Cara Ebbeling of Harvard Medical School.

It may not sound terribly impressive — four pounds in a year. But these teens were counseled to change just one thing: their drinks. It's the best evidence yet that swapping sugary drinks for zero-calorie options may influence weight significantly.

Yet there have been some concerns that diet soda might increase our appetites and prompt us to eat more. Well, a recent study suggests this is not the case, at least in the short term.

Danish researcher Bjorn Richelsen of Aarhus University Hospital compared what happened when volunteers drank Diet Coke, water, milk and sugar-sweetened Coke.

"Our conclusion was quite clear," says Richelsen. Sugary coke led people to be slightly hungrier and to eat more. But Diet Coke had a more neutral effect on appetite. Volunteers did not increase their caloric intake in the four hours after drinking Diet Coke.

"We found if you're drinking soft drinks without calories it behaves [on the appetite] exactly like drinking water," Richelsen tells me.

Now, longer-term studies are needed to see if this neutral effect holds up, but it's redeeming for those who feel diet drinks are a helpful strategy.

None of the researchers I interviewed for this story recommend we run out and buy diet drinks, however. They all agree water is best.

"We're still learning a lot about diet soda," says Robert Lustig of the University of California, San Francisco.

He's been pushing for Americans to make drastic cuts in sugar consumption. And he says since liquid calories — in the form of soda, juices and sports drinks — account for about one-third of the sugar we consume, he suggests cutting them out is a good start: They are the low-hanging fruit.

"If you got rid of 33 percent [of calories by eliminating sugary drinks,] you'd be knocking our added-sugar consumption down from from 450 calories a day to 300 calories per day [on average]," says Lustig.

Not an insignificant reduction. He says if diet soda is the baby step to wean people from sugar, maybe that's not a bad thing.

"I liken diet soda to methadone," he says — the drug used to wean people off heroin. Not ideal, but perhaps effective.

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And I'm Steve Inskeep.

Today in Your Health, the teenage brain - which is not as bad as you may think. First, the fuel on which many American brains run, for better or worse - soda. Seems more Americans have gotten the message that sugary drinks are doing their waist lines no favors. As more people cut back, there's been a steady rise in consumption of diet soda. NPR's Allison Aubrey looks at whether swapping one for the other really pays off.

ALLISON AUBREY, BYLINE: If you focused on changing just one thing, one strategy in your diet in order to move the needle on the scale, what would it be?

CARLETTA GIRMA: For me it would be I would stop eating junk food at my desk at work.

AUBREY: Junk food, like what? Chips, soda?

GIRMA: Chips. Chips.

AUBREY: That's Carletta Girma, who was eating lunch out with her friend Julie Ost.

JULIE OST: We were just talking about this. I was talking about the candy bowl at work. I know where two candy bowls are at work, so that would probably be the elimination.

AUBREY: Not a bad strategy. Those would be empty calories. But interestingly, neither mentioned all the liquid calories they consume each day. Carletta says she's addicted to caramel sweetened coffees and when it comes to soft drinks?

GIRMA: If I drink a soda, I drink the real deal - Coke. I feel like if you're going to go for it, go for it.

AUBREY: So I asked Carletta what if there were good reasons to believe that these sugary, liquid calories were particularly significant when it comes to body weight? Would she be willing to listen?

GIRMA: Absolutely.

AUBREY: So here's the theory of a lot of experts, including Cara Ebbeling of Harvard Medical School and Boston Children's Hospital.

DR. CARA EBBELING: I think that consumption of sugar sweetened beverages may be a particularly high impact behavior when it comes to controlling body weight.

AUBREY: To test this theory, Ebbeling and her colleagues recently completed a big study designed to measure just this one thing - the influence of sugary drinks.

EBBELING: So we recruited adolescents who were drinking at least one sugar sweetened beverage per day.

AUBREY: All of them were overweight. And for an entire year these teens and their families received home deliveries of diet soda and water, and they were counseled to avoid sugary drinks. At the end of the year, Ebbeling says, these teens who'd been on a trajectory of weight gain had gained significantly less weight compared to a control group of teens, who had continued to drink sugary drinks.

EBBELING: We found that there was a difference of just over four pounds.

AUBREY: Just because of the differences in drinks? Nothing else about their diet, presumably, changed?

EBBELING: That's correct. We did not counsel around anything else.

AUBREY: This is some of the strongest evidence yet that swapping sugary drinks for zero calorie options can influence weight significantly. But there's still some resistance to the idea that diet soda is the healthy option. Friends Carletta and Julie say they're still not ready to switch.

OST: No. No. It's really hard to really understand what it does, physiologically, in the body.

AUBREY: For instance, earlier studies suggested that perhaps drinking diet soda somehow leads people to eat more. And Danish researcher, Bjorn Richelsen, told me the Danes have had the same concern.

BJORN RICHELSEN: We had the idea, for sure, that diet soda would enhance appetite.

AUBREY: But Richelsen says this is not at all what he found when he studied it experimentally. He compared what happened when volunteers drank Diet Coke and when they drank water. He measured how this influenced hunger hormones.

RICHELSEN: We also measured what they were eating four hours after.

AUBREY: And he says, what he found was very surprising. Sugary Coke led people to be slightly hungrier, while Diet Coke had a more neutral effect on appetite. It did not lead people to eat more at the next meal.

RICHELSEN: Our conclusion was quite clear. We found that if you're drinking soft drinks without calories, really, it behaves exactly as drinking water.

DR. ROBERT LUSTING: We're still learning a lot about diet soda.

AUBREY: That's physician Robert Lustig of U.C. San Francisco. He's been pushing for Americans to make drastic cuts in sugar. And he says since drinks in the form of soda, juices and sports drinks account for about a third of sugar we consume, they're the obvious place to start.

LUSTING: If you got rid of 33 percent, you would be knocking our added sugar consumption down from 450 calories a day to 300 calories per day.

AUBREY: And so, he says, if diet soda is the baby step to wean people from sugar, which he argues is habit-forming, maybe that's not a bad thing.

LUSTING: I kind of liken diet soda to methadone.

AUBREY: The drug used to get people off drugs. Not ideal, but perhaps effective. He still thinks drinking water is best, as do all the researchers I interviewed here. And friends Julie Ost and Carletta Girma say, well, maybe.

GIRMA: I could save a lot of money if I just drank water only.

AUBREY: But part of the pleasure of drinking soda is the ritual, she says.

GIRMA: You like to pop the can or open the bottle. You like the sound of the bubbles.

AUBREY: So maybe it needs to be bubbly water.

Allison Aubrey, NPR News. Transcript provided by NPR, Copyright NPR.