Eat healthy, lots of fresh fruits and vegetables, salads with nuts and beans (kidney, garbanzo, etc...complex carbohydrates), lean protein, hydrate a lot, cut out all junk food and artificial sweeteners (the latter trick your body into thinking it has energy when it doesn't), skip the burger joints, start reducing your sugar intake (fruit juices are pure sugar in the form of fructose), eat multiple small meals a day, don't eat after 9pm, find a good probiotic for gut health...
My daughter has been a nutritionist and certified personal trainer for 17 years. She says that the most complete BALANCED diet she's ever encountered was the LA Weight Loss Diet. No fads like zero carbs or zero fats or other such "Atkins"-like stuff. She recommends it as a very good, balanced food intake program.
There are other pre-TKR discussions on the Forum that discuss preparing your house (get rid of throw rugs), kitchen, bathroom, etc. However, you must prepare yourself for this event, and its aftermath, mentally, emotionally, physically and spiritually...ALL of the above! You need to go into this with eyes wide open understanding the very likely possibility of a lot of pain, heavy-duty meds, interrupted sleep, lots of painful PT work and subsequent strength exercising. You need to prepare for a year-long recovery and be thankful if you get past it sooner than the rest of us. There are expectations of what this will be like and then there's the reality. I truly hope that your DNA does not produce any scar tissue and that you skate past this in 60 days...highly unlikely but we all pray to be that one special case who gets away with it.
Click on my picture and then "See All Discussions". I have lots of posts out there that could be of help (meds, sleeping, post-op depression, exercising, expectations, etc.). Also, there's a lady named Jenny on here who has a fabulous off-site blog on her experience. Lots of other Oracles (#6's) on here like OldFatGuy1 and MartinNavello (I probably screwed up his handle) that have more great discussions posted. We're here to help. Stay in touch.