There's a lot of debate certainly about the chemicals in diet soda, and it's hard to tell what we really know about its effects on humans. There are lots of chemicals in many of the foods we eat too, many of which may have negative effects. Again, it's hard to know.
Many of us choose to drink and eat these items, even knowing these effects may be possible.
I'm glad to hear the OP cut out the sugary soda with all its calories. Some time later on, she may decide to make other beverage decisions, but that's her choice to make.
However, I also agree with some others here. I personally have never lost weight from exercise alone without altering my diet. I have lost some weight by changing my diet alone, though it was very very slow. Once, I had restricted calories until I was losing about a pound every other day even without exercise, but I felt like garbage and it quickly failed.
In my non-professional opinion, you should always count calories or monitor food intake, swapping unhealthy calorie dense foods with healthier foods AND maintain at least 30 minutes of cardio a day, as well as a few days of weight training a week. People who say 30 minutes of cardio is worthless are wrong. You can spend 30 minutes sitting on your butt or you could spend 30 minutes working out. Working out will burn more calories and make your body healthier than sitting on your butt.
Getting rid of soda is a decent enough idea, but for me it stems mostly from the idea that soda starts replacing your water intake. I treat soda like a junk food. It's akin to a bag of chips or something even if it's diet soda, because it isn't contributing anything to my body besides having something to put in my mouth, give me a caffeine kick and, I'm not gonna lie, I like the burping. Switching from regular to diet soda is definitely a step in the right direction. After that, if you want to, start replacing that with flavored water, tea or 1/2 and 1/2 juice (my favorite!).
There are folks here who have lost huge amounts of weight and kept it off all while maintaining a serious diet soda addiction. I don't know anyone who has done it while drinking regular sodas. No one will ever argue that diet soda is good for you - drink water!!!! - but you can lose weight while drinking it.
There are also people who have lost beaucoup pounds without much exercise (I'm down 90 pounds so far with no regular formal exercise. I take the dogs for a leisurely mile or so walk most day, sometimes I do a half hour on the Wii Fit (which is hardly exercise but is doing more than sitting on my ever shrinking butt). But I've only met one person here who lost more than a few pounds just by exercise (there was a lady here last year who had lost about 40 pounds just with exercise but then she hit a wall and *had* to start eating carefully to keep losing.)
Exercise is great - muscle looks better than flab and burns more calories per pound - but it won't get you very far without watching your food intake.
I don't know what to tell you, but here's my story - a couple of years ago, I reached a weight loss of 100 pounds. I did this by counting my calories, exercising regularly, and also doing weight training. I hit that 100-pound mark in the fall of 2008, and then 2009 came around, and honestly, it was one of the most hellish years of my life where everything seemed to go wrong. I wasn't strong enough to resist going back to my old habits, and I started eating a lot more, and not taking note of what I ate. I'd eat a jar of Nutella a day, for example, that's the only thing I'm sure of. But calorie counting fell by the wayside.
I did, however, keep up exercising every day, and I still gained back 49 of those pounds I lost. I was pretty disappointed with myself, and early this past October I decided to get my weight back on track, and went back to counting calories, exercising regularly, and weight training. Since early October, I have lost 21 of those pounds I gained back. I may have lost even more except I backslid a little during Christmas when my father died rather suddenly and I didn't do any calorie counting and exercising. I am back on track now, however, and losing again. I guess my point is, like some others here, I had to do both (pay attention to what I ate, and exercise) to lose.
There's a lot of debate certainly about the chemicals in diet soda, and it's hard to tell what we really know about its effects on humans. There are lots of chemicals in many of the foods we eat too, many of which may have negative effects. Again, it's hard to know.
Many of us choose to drink and eat these items, even knowing these effects may be possible.
I'm glad to hear the OP cut out the sugary soda with all its calories. Some time later on, she may decide to make other beverage decisions, but that's her choice to make.
True but it's a well-known fact that anything artificial is generally unhealthy, which is why I do my best to avoid artificial anything. I was once told 'if you can't pronounce it, don't buy it', and if you look at the label of a can of coke, that applies.
I have a colleague that is genuinely addicted to diet coke and it's damaging her health. She eats relatively healthy, exercises regularly but drinks at least four cans of the stuff a day. Her skin is terrible, her hair is terrible and she gets headaches when she drinks it, which tells me that something in it is having an adverse effect on her.
Of course, choosing your own drinks is up to you, but I know I'd rather quit the stuff permanently because of all the artificial yukiness that's in it than trying to justify that diet drinks are better.
Lots of people lose weight with diet and no exercise. I don't know anyone who did the opposite. Exercise is important, but it is not going to make you lose weight without changing your consumption.
The only way this used to happen to me was when I would run 2 hours a day in the wilderness behind my house and then go to work and my job was heavy lifting for consistenly for 8 hours. I ate jack in the box every day for lunch and still lost. I think the theory is if you are doing what cavemen had to do to survive and catch their food a million years ago you should be able to eat whatever you want. Modern human beings, however, should definately watch calories and excercise. It's just common sense.
I have a colleague that is genuinely addicted to diet coke and it's damaging her health. She eats relatively healthy, exercises regularly but drinks at least four cans of the stuff a day. Her skin is terrible, her hair is terrible and she gets headaches when she drinks it, which tells me that something in it is having an adverse effect on her.
Of course, choosing your own drinks is up to you, but I know I'd rather quit the stuff permanently because of all the artificial yukiness that's in it than trying to justify that diet drinks are better.
I drank diet coke a lot. More than 4 cans, and it had absolutely NO effect whatsoever on my hair and skin. However, if your friend drank only diet coke and was dehydrated, yep. Her skin and hair would look awful, at no fault of the diet drink. Headaches? Yep. You can get them while drinking coke, but I'm guessing it has more to do with caffeine than anything. She could have a sensitivity to some ingredients, but headaches due to caffeine are much more common. Addictive? Yep. Anything that contains caffeine is addictive. Coffee, tea, sodas... Even chocolate has small amounts of caffeine. So being addicted to diet drinks, I'm sure, has more to do with the caffeine than the artificial sweeteners.
I'm not saying diet drinks are a God-send, only that they ARE better than swigging back regular sodas when you are watching calories. I think the OP has as much right to her soda than the rest of us have to our occasional chocolates, french fries and other "bad" foods. She's not "bad" because she drinks them. It's not going to make her hair and skin look terrible if she drinks them. It's just one more thing to factor in when trying to find a plan that works for her.
A little more about my lifestyle. I eat 2300 calories a day sometimes less, however, I rarely used to include the sodas/coke in my diet, which is 1 of the main reasons why I think I became big.
I personally need to cut the calories by removing the sodas, I have an anaerobic body which burns fat faster than aerobic bodies, this makes me able to do short bursts of exercise as opposed to 1 hour sessions. I am not sedentary as a person, however, I found why when I tried to exercise last week to knock the weight off, wasn't successful. Dr wants me to go for a blood-test today because she thinks I might be more pregnant than I realised at first. This is why I don't want to eat less than 2300 calories a day, the Dr doesn't advise it either, which is 1 of the ultimate reasons why I want to do this via exercise. However, I had to do 30 minutes a day as opposed to my usual 90 minutes a day (before my first baby) because I have a problem with blood pressure this time around.
So, I am starting to think maybe I should be looking at lifestyles changes for pregnant women instead! I think I read that there's a few posts on this site which cater for pregnant ladies?
Switching from regular to diet soda is definitely a step in the right direction. After that, if you want to, start replacing that with flavored water, tea or 1/2 and 1/2 juice (my favorite!). 
