I am so over reading a new study each week about diet soda. First, it's deemed as this totally evil drink making everyone get fat and get cancer. Now, researchers are claiming diet soda can actually help you lose weight. What are we supposed to believe? Research against diet soda.
In an 11-year-long study researchers found that drinking two diet sodas a day is associated with a two-fold increased risk for kidney decline. Kidney decline was not associated with sugar-sweetened sodas, so researchers suspect that the diet sweeteners are responsible.
One of the longstanding criticisms of diet soda is that the artificial sweeteners screw with your brain and make you actually crave sweets more. Artificial sweeteners can trigger insulin levels to rise which send your body into fat storage mode and can lead to weight gain.
The acid in diet (or regular) soda can rot your teeth out. Research compared the mouths of a cocaine-user, a methamphetamine-user, and a habitual diet-soda drinker, and found the same level of tooth erosion in each of them.
The Study Claiming that Diet Soda Helps with Weight Loss.
First, the study was funded by the American Beverage Association. They took 300 current diet soda drinkers and divided them into two groups; one group continued to drink diet sodas and the other group had to stop. For three months both groups received the same coaching on weight loss techniques, and feedback on the meals they logged in their journals. At the end of the three months the diet soda group lost an average of 13 pounds, and the no-diet soda group lost an average of 9 pounds.
This one short, fairly small study, is now being used to say 'drinking diet soda helps with weight loss.'
No, those current diet soda drinkers who are told to go cold turkey didn't lose as much weight as those people allowed to still drink diet sodas. Perhaps they would have lost more but they were going through caffeine withdrawals and ate more to compensate. Research has shown that most people have a finite amount of willpower and trying to do two big things at once, losing weight and giving up a diet soda habit, could just be too hard for most people to do effectively.
The problem with correlational research.
The #1 thing that all good psychology classes should teach you about correlation is that correlation does not imply causation. Just because two things happen at the same time, or vary together, doesn't mean that one actually causes the other. Take this study from the University of Texas; diet soda drinkers had a 70% greater increase in waist circumference compared with non-drinkers. Participants who drank two or more sodas a day experienced a 500% greater increase. That doesn't mean drinking diet soda caused the people to gain weight. Perhaps those people who drink diet soda make less healthy eating choices then those people who don't drink diet soda. Maybe their insulin levels are rising and causing them to crave more foods. Or, they could feel 'justified' in eating more because they are drinking zero calorie beverages. Point being there are far too many alternative explanations that's it's not valid to make a blanket statement like 'drinking diet soda causes weight gain.'
Another example of correlational data that could be used to make erroneous claims. A study presented at a the American Academy of Neurology meeting found that over the course of 10 years, people who drank more than four cups or cans of soda a day were 30% more likely to develop depression than those who did not drink soda. Well, if the above research is correct then maybe they have depression because they are overweight, have a host of health issues, and their teeth are rotting out, not 'because' of the diet soda itself.
I make a perfect example. When I was at my heaviest I drank diet soda daily. Now, 50 pounds lighter, I rarely drink it. So, was the diet soda at fault? Absolutely not! Diet soda didn't make me fat. Binge drinking, eating processed foods & never exercising did.
So, what should you believe?
I love this quote from one of the participants in the 'diet soda can help with weight loss' study who was in the 'no-diet soda' condition:
I feel like I could 1000% tell the benefit of drinking water only. I felt better, I had more energy, I felt healthier, I just generally felt way better. I can feel the difference now when I drink a diet drink, I can feel this 'heaviness'.
With so much conflicting evidence I know it can be hard to try to make the 'right' healthy decisions. I think we can all agree that drinking water is better than diet soda. If you are currently drinking a lot of diet soda a day and you are trying to lose weight then it seems accurate to say you should cut back gradually and start replacing diet sodas with water or tea. Overall, I hope that most people can see that despite what the news headlines may proclaim there is nothing about diet soda that will help you lose weight.
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Are you a diet soda drinker? What do you think about all the conflicting research?