Matt,
The Keto diet is potentially a problem for kidney donors because of the high fat and protein orientation, which is tough on kidneys. I'm not sure about the fasting diet.
I used Weight Watchers a couple of years ago and lost 15 pounds. You log in everything you eat during the day, managing your intake up to a daily point limit (there's some carryover and weekly points, too). The point system steers you toward lower fat foods like fruits and vegetables and away from carbohydrates and fats. You have complete control over what you eat, and the WW system monitors how much you eat. There are different plans, and the one I did was $20 per month.
If you have medical insurance, you might see if you can get nutritional guidance through the plan. Another option would be to schedule a regular physical exam, which should be provided with no out-of-pocket expense as preventive care, and ask your doctor for guidance.
Finally, if you have a Facebook account, you might post in our group there to see what others have done. These days, we have much more message traffic on Facebook than we do here. Alternatively, I can post something on your behalf and share the results here.