Though most people will think of dietary interventions when they hear the word 'paleo', it is actually more aptly applied to the concept of sleep. I say this because sleep is even more foundational to the proper functioning of the human body than diet or exercise.
Where diet and exercise can and should be used to bring the human body to the highest level of function possible, proper sleep is foundational for even the most basic of human physiological functions. Furthermore, if sleep is not optimized, there is no amount of diet or exercise that can pull you out from the ditch of metabolic and hormonal dysfunction.
Many people fail to recognize that our need for sleep - as well as our sleep patterns themselves - evolved in concert with the rest of our biology. Many in the Western world consider it a point of pride or a sign of toughness when they boast about living and "functioning" on little sleep.
Others will look at these people and ask themselves, "how do they do it?" Well, the short answer is, they're not "doing it".
Consistently operating on little to no sleep is like robbing the future you to pay the present you. The payment that present you receives is that of the perception of toughness, and perhaps also the short term benefit of more money from working more hours (or whatever other perceived benefit you enjoy). The future you however, is being robbed of the ability to live without Alzheimer's disease, as this is the tragic common result of a lifetime of poor sleep.
This is simply another example of a trade-off in evolution. You can always take what you want in the moment, but you will always be forced to pay for it later. Biology is like a debt collector, it never forgets the debts you incur throughout your life, and it only forgives if you honor the reality of it's existence.
Sleep is the single most important biological account for you to manage (8 - 9 hours per night). After this, diet and exercise are of equal importance - especially after the age of 30.
Within the context of exercise, what we really care about is increasing muscle mass over time - if only a little bit. Reason being, after the age of 30 we begin to steadily lose muscle mass at a rate of approximately 0.5% - 1% per year. This means that if you're standing still, you're actually moving backwards. The likely reason for this is because 30 years would have been considered old age in our evolutionary past, and our genes would either have already been passed on, or they weren't going to be passed on at all, and we would have started to degrade. This isn't a perfect 1:1 ratio and 30 years is only an average benchmark due to high infant mortality, but it helps to understand this process from an evolutionary perspective.
Although an optimal diet looks something like "eating only fresh meats and greens" - especially if recovering from illness - there are a wide variety of options here as there cannot be any one single way to eat - all things being equal. As long as you're able to recognize and observe the template of a real food diet, you do not have to religiously adhere to it 100% of the time.
That being said, if you're new to the concept, I recommend being as stringent as possible for as long as you can. For me, this was about 3 solid years of Paleo eating.
Over the years I've come to realize that the "all at once overhaul" is probably not a good idea. Of these three critical components, (sleep, diet, exercise) I recommend only drilling deep on two of them at a time - if that. Reason being that you are a complex system, and there is no telling what can happen if you perturb your behavioral patterns too much at any one time. To be clear, you're allowed to work on all three at the same time, but it's better to think of it as a triage system, where you're concentrating attention on that account closest to bankruptcy.
At any given time, one of the three accounts is probably in need of more attention than the other two. If you work diligently to top it up, you can begin to live a healthy lifestyle much quicker than you might think.
Best of luck!