So I did a little self experiment after hearing lots of people do well on keto or similar while including diet soda. I ate at 3am 1/17/2018 and fasted until 3am 1/18/2018 (work overnights and sleep from 12pm-7pm) and at 5am 1/18/2018 I had 1 20oz diet dr pepper and literally within 20 minutes have SO MUCH all over body pain. Knees hurt again mid and lower back are KILLING me and just feel painful. I drink 9 liters of water every day no exception and was already in 6 liters when I had the soda. Man… wont do that again!
Ps… It also really bloated me!
Diet soda experiment
Nick224
(Nick Eagle)
#1
PaulL
(Bacon is a many-splendoured thing)
#2
Sorry, buddy, but at least now you know. It’s probably an effect of the aspartame. Stick to plain water or seltzer.
widebody
(Gargantuan B. Widebody)
#3
On my last run at keto I had gone 6+ months with a diet soda. The first sip was like drinking battery acid. But for reasons I can’t explain I kept drinking it. An hour or so later I regretted it. I got some bloat, some pain and my stomach was less than pleased with me. 
Sometimes you have to experience the dark side to really appreciate it. Just telling me something doesn’t always drive the lesson home.
Nick224
(Nick Eagle)
#4
Just woke up and my body feels like I did an intense HIIT session and serious full body workout! Going high fat today and definitely not having any more soda!
KetoKnitterNZ
(Michele)
#5
That is an extraordinary response! Hiw awful. I’m so glad I’ve not drunk diet soda - I hate the taste of the artificial sugar so never been a fan.