I’m no expert, at all.

My guess is you may not have adequate In take of probiotic foods.

I’m very droggy, but wanted to respond. Please forgive.

Think of ditching soda or at least limit it to four days a week. No particular reason for the number.
While you can counter the I’ll effects of diet drinks, with probiotics. There is yet another approach. Drink water for it’s PH benefit. I struggle with water, only because I was raised on cola cola. I just don’t enjoy water, I don’t hate it , I just prefer my drinks to have flavor.

I choose to start drinking teas, that don’t require sweeteners. Coffees so thin. Then I discovered stevia.
I started putting fruits in my waters, especially orange and lemon with my ow stevia at restaurants. Further on after reading about anti oxidants I began to put fruit high in anti oxidants into my waters and teas.
About once a week I get a soda and wow. I love it. However i think of soda as something that should be on top of the food pyramid – used sparingly. Reason is that in my OPINION diet soda should be used in moderation so it won’t over influence probiotics. I’ve read that some stomach bacteria ratios can cause cravings. That the dominate bacterias somehow effect satiation. So even though the diet soda isn’t harmful by it’s self. The diet soda can lead to habits especially the craving for starchy foods. Starchy foods are super calorific if you get what I mean.

I changed my diet from high calorie starchy foods to recognizing vegetables as first choice to get my carbs.
I changed my thirsts to water, green teas, and antioxidant drinks. Especially ginger and gensing. Also pineapple to aid in burning fats in the digestive system. Not really sure about the pineapple, but my family enjoys the deal I make over it . Instead of old habit of ice cream family time. It’s said to help target fat in the digestive system. Search/read benefits of raw pineapple. I juice a whole fruit and pour into ice trays. It’s fantastic on non fasting days when I have 500 cal left on my TDEE.

To be honest I haven’t bannished all sodas and starchy foods. I just try to keep it simple by not consuming them on my planned fast days 4:3 Monday, Wednesday, and Friday. Basically low energy day, followed by high energy day. With free choice on weekends. I imagine I may be weaned away from comfort foods in a year or two. As my palate changes over the next few years to healthy as possible foods, or foods that are not a combination of sugar, salt,vinegar,msg, and or fat as a natural flavor.

True that diet drinks are zero calorie, but diet soda is not a zero effect on the human body. Its zero nutrition value with it’s very acidic PH may cause craving for breads, pastas, and potatoes.

If it’s not about probiotics? You may have decided to exercise a little more. I would suggest seasonal training. Meaning not do the same exercise forever, because the human body with adjust and plateau.
Every two months change your main exercise. Indoor cycling, skipping rope, cycling, walking, rowing, jogging, compound lifting, dancing, boxing.
If strenuous exercise is not possible, because on sedentary reasons. I can speak from experience, squeezing a stress ball in my hand, standing or sitting on exercise ball while watching tv. Bouncing a ball. Calf raises. And a bunch of non impact movements while sitting can increase metabolism easily. 600 calories was my goal. To increase my N.E.A.T. I can’t recommend what I did to anyone. In 2013 while I was in hospital bed after an accident. 4:3 600 calories consumed 600 calories of exercise throughout the day while laying. I kept off 27lbs on the anniversary of starting a variation of 5:2
No worries 2014, I’m strong enough for strenuous labor in warehouse.
This year I weigh in once a month so I don’t get discouraged. I lost 3 lbs in four weeks starting this year in march. Last time I weighed 244 was 14 years ago, 1999 I yoyoed from 255 down to 201 up to 260 and got a fatty liver. Not doing that again!

Sorry for the long and winding speech.
Best wishes.

I got myself a Sodastream machine last year and it has been a godsend on this diet. I have fizzy water on tap, and it is very refreshing with a few drops of lemon or lime juice in. You could make it sweeter with some stevia, which you could gradually reduce to ‘re-educate’ your palate!
Carbonated water (especially with citrus added) is slightly acidic though but not as bad as the acidity of colas.