Dr. Mark Hyman has an interesting point about sweetness in general. Sweet tastes trigger hormones that affect satiety and can interfere with actual healthy eating.

Not exactly sure why you want to sidestep the artificial sweeteners (which even if benign chemically probably affect taste->brain communications), the phosphoric acid (which may affect mineral balance in the body), and/or the caramel coloring (which is linked to cancer).

But regarding your question, I don't think diet sodas contribute to holding onto fat (don't see a mechanism aside from causing increased eating as a result of the sweet taste and no calories). Nor do they likely contribute to water retention since given the caffeine and the very low levels of sodium, if anything, they are essentially diuretic in nature.

Artificial sweeteners are like methadone for sugar. For reals. I had a sugarfree gum episode a few months ago, and it made me crave sugary sweets like crazy.

In my experiences, I've absolutely retained water from diet drinks. Carbonation has done that to me, for sure, and especially causes bloating.

Robb Wolf calls this the "Food Porn" effect. Your body "gets ready" for the onslaught of sugar when you taste something sweet. So even non-caloric, non-glucose sweet things can have an insulin effect. In fact, some people will start releasing insulin if they look at something sweet (hence, the term Food Porn). And since insulin is the "fat storage" hormone, it's totally reasonable to believe that non-caloric sweet things can cause you to store fat via insulin.

But the bigger issue is, do you really want to be drinking 4L of ANYTHING a day?

http://www.huffingtonpost.com/2011/06/29/diet-soda-weight-gain_n_886409.html

"In the first study, researchers collected height, weight, waist circumference and diet soda intake data from 474 elderly people who participated in the San Antonio Longitudinal Study of Aging. They were followed up an average of 9.5 years later, according to the research.

Researchers found that the diet soda drinkers had waist circumference increases of 70 percent greater than those who non-diet soda drinkers. And people who drank diet soda the most frequently -- at least two diet sodas a day -- had waist circumference increases that were 500 percent greater than people who didn't drink any diet soda, the study said.

Artificial sugar didn't produce any better results in the second study in mice. Researchers for this study found that diabetes-prone mice that were fed a diet that included aspartame for three months, had higher blood glucose levels than mice not given aspartame.

This isn't the first news illuminating diet soda's health risks. A study published earlier this year found people who drink the beverage every day have a higher stroke and heart attack risks. And UK researchers found earlier this month that sugary drinks can dull taste buds, leading consumers to crave the sweet stuff even more."

I am so glad my mom never let us have soda. Best parenting move ever. Now I don't even have to think about them, and it must suck being used to having them all the time and trying to stop.

The biggest issues here would be triggering a desire for sweet food, and possibly water retention. Plus, I thought that thing about formic acid from methanol production leading to problems with eyesight was pretty much a myth, but then I had a prof use it as an example in biochemistry, so now I am relatively freaked out by aspartame in general.

Clinical update for concerns about "headaches, seizures, blindness and cognitive and behavioral changes with long-term high-dose aspartame": http://www.ncbi.nlm.nih.gov/pubmed/2667892

Just watch Sweet Misery, enough said.

How is Zevia soda? The grapefruit is my fave! I know it shouldn't be an all the time thing, but how bad is it, really, every once in a while? Like a couple cans every 1-2 weeks.. I know stevia is shunned by some in the Paleo community, but I haven't ever figured out why. (With the exception being the highly processed versions, like Truvia).

I don't know the answer to your specific question. But, any addiction is bad. It sounds like you are drinking loads of diet soda.

Do you have fat to lose? If you do and you are unable to lose it then why not do your best to avoid or at least limit your diet soda habits and see what happens?

I am not 100% sure myself but I have been an avid diet soda drinker myself. I've given it up before and saw drastic changes in my skin. I've always had really great skin in the sense that I do not have acne, but when giving up diet soda my skin became more soft and even.. I had some weird discolored spots on my back that also went away when I replaced 4-5 sodas a day with just water.

I since slipped back to them and the same dry skin/sploch skin is back.. so today is day one of being off them. From here on out I intend on making them like a 1 a week thing if any at all.