Ima guess they mainly mean exercise, but also sleep.

Personally I obsessed about diet for a decade before I finally got religion about running for 30+ mins every day coming up on 2 years ago(I now typically run for more like an hour). It has made far more of an impact on my well being than any diet or fasting regimen… which, mind you,I was extremely strict about, like eating disorder levels of obsession. It has also made catching quality sleep a complete non-issue. I won’t lie, it took many months of consistency to feel these benefits, and I personally didn’t really see them when I was doing cardio only 3 times/120mins total per week on a bike and resistance training. My understanding is that this is probably a result of metabolic adaptation. Much the way I learned that the bacteria in your gut is a culture you grow and maintain, happy gut = happy me, I now think of my muscle mass as a crucial metabolic organ that needs to be properly conditioned for my bodies energy systems to function properly. Strong metabolism = little metabolic waste accumulating in your tissues and more of the machinery your body needs to work.

Unfortunately we live in a society where you have to make this a lifestyle, I personally find I have to keep my run very high on my list of personal priorities to stay consistent, as it is rather disruptive to my day. I have reflected that a lot of that is around cultural norms, so if this sort of routine was much more normalized it would be easier to integrate socially while still maintaining it. Sweaty people are only really annoying if you aren’t sweating with them. With how much sharper, more energetic, and emotionally regulated I feel, it amazes me that more employers don’t incentivize it-maybe someday.

That said, I’m in my mid 30s and I’ve never felt better in my life, so I’d say it’s worth while. I feel strong, faster, and much more durable, with virtually no pain and less illness/infection/inflammation than I had even in HS. Meanwhile my contemporaries are complaining of back and knee pain, frequent illness, poor sleep, dietary intolerance and out of control and appetite. They say, “I’m getting old” and I just shake my head.

I know it’s cliche as hell to say we were born to run, but seriously, our species almost certainly has an evolutionary legacy of running a lot, and I think many of us can tap into that legacy if we so desire.