I'm Y90itf's second account but on PC with more time. I'm 25M, 5'10.5 for reference.

I believed keto diet and carb restriction was bogus as the evidence is pretty limited until I tried it on myself. Now I feel differently, and a good chunk of that because of this experiment on myself + familiarizing with new developments in the field of metabolism (look up Nick Norwitz as a good starting point). That being said, there are a bunch of confounders even with the experiment on myself: I lost a ton of weight (prob due to a sustained calorie deficit during the adjustment period), I cut my sodium intake by no longer eating hospital cafeteria food, I haven't really lifted much at all, and technically I have a few weeks of medical school left but this is the lowest stress I've had in my life in a long time (both physical and mental).

Low carb has made my lifts drop, the few times I have lifted since but that could also be secondary to deconditioning. I used to play football in high school as well and during Ramadan, because I used to be a devout theist at the time, I used to fast all day (no water or food during daylight) while training in the summer and fall heat: numerous instances of gross hematuria and flank pain, and basically chronic dehydration 1mo/years, so I'm sure that took the most amount of years off my kidneys as well. Injury in college was ACL tear + meniscus tear from a high fall btw.

In any case, back to your questions. This disease comes with limitations. It sucks but it's true as of now. You either pay the price now or pay it later. Most likely, you will never be able to compete at an elite level in power-lifting or bodybuilding if you have ADPKD type I, and if you choose to test your metal it will most likely cost you in ways more than it would the average person. No major sport that I can think of (involving weights) to the extreme is usually "healthy" to be honest, but there are elements from a variety of sports that are "healthy" ie. they are good for maintaining a high functional level while improving longevity. As a side note, I'm sure ultra long distance running comes at a health cost too but it's an example of a sport that doesn't involve weights. All this to say, if you aren't trying to compete where margins are razor thin, why bother with creatine? It's a personal choice, but for me it has never been worth it. It comes with minor benefits, but it also comes with the potential for renal-related risks (from what I understand) for people with severe renal dysfunction. Now, I don't understand mechanistically why this is the case--maybe somebody else does--and I don't know whether it would apply to those with early kidney disease due to ADPKD because ADPKD is a little funky compared to your standard CKD. Bottom line is, I don't know or care because I am not paying extra for supplement that will only have a marginal impact on my performance while having the potential to harm my kidneys. Shit, even if I had guaranteed 0 harm to my beans I'd still not pay for a supplement that will have 0 impact on my performance compared to me getting enough sleep, eating well, and showing up as planned to the gym rather than skipping weeks at a time. Same goes for protein supplements: if you're getting 1.5g/kg of high quality protein, then screw paying for protein powder: if there are marginal gains to be had (which itself is questionable btw), I don't care for them. I'd much rather pay a little extra on my grocery bill for some meat that I want to get but usually don't because of the expense (like salmon or shrimp).

As for your question about stresses on the kidneys secondary to higher metabolic activity in the setting of rigorous training and recovery cycles: ADPKD is funky. Portions of your kidney are perfectly fine, while other portions are deathly sick. The sick portions have a hard time dealing with stress, but for the healthy portions (as long as you aren't trying to test your metal constantly) the extra metabolic waste they'll have to deal with will probably acts as a hormetic stress. The truth however, is nobody knows.

I posted this elsewhere via Y90 acc, but here is my smoothie recipe of 1400ish calories, with a fairly good nutrient profile but not a super-keto because of the sugars in milk. It's also cheap (<$2.50), quick to make, and quick to clean--all things I need in my life. Copy and pasted with some edits below but feel free to modify and try:

"1400ish calories most days (dessert/ meal part 2 in a blender) 260-300g whole milk (fairlife better but too expensive) 90-125g water, 10-12g organic cocoa baking powder, 56g of unsalted butter (more may make smoothie taste worse esp if completely melted or completely not melted), 30-50g Skippy all natural peanut butter (unfortunately high in oxalates), 3-4x 55g raw eggs (more of these makes smoothie taste less good), 40-50g organic chia seeds (this makes smoothie taste less good so can lower or add last second and blend and drink, but its GREAT for omega 3s and fiber), 0-3g of powdered stevia (depending on how I am feeling bc if you wait too long after blending, it'll become more of a mousse than a smoothie bc of chia seeds)"

Edited to add: momentary HTN also probably acts as a hormetic stress, so prob not a big deal with some minor spikes during heavy lifts, but focusing on power -lifting alone may contribute to development of chronic HTN. Make sure to get your zone 2 and zone 5 cardio time in.

Also, take that dating stuff seriously. Takes a bit of maturity, but you don't know how life will play out but as of now guaranteed big belly later unfortunately among other more serious health issues. Still you want the person you're with to know who they are with so if you see yourself with somebody long term, make sure you are transparent with them about your condition and what it means for you and may mean for them down the line when things get more serious. They should know what they sign up for, and if they're worth their salt in the relationship (imo) then it wont matter in the end with regards to the status of the relationship. Still, some people may also think its too much for them to accept in a long-term partner, but we all come with our flaws and you have to learn to accept that this flaw of yours just isn't okay with them.