I know this for sure.
This is true for all things, including your body. You must nurture it, work it, rest it. If you don't, the energy spent on neglect will eventually turn on you. It's not personal, just physics. For years my trainer, Bob Greene, tried to teach me this principle. I understood it intellectually, of course, having exercised (almost) regularly since I met him 14 years ago. I've been consistent over the years about hating every minute of it. I understood why I had to work out (to not have a fat tush), but I didn't "get it" until this past Christmas in Africa.
I'm building a leadership academy for girls near Johannesburg, and I had traveled there to choose a principal and to offer Christmas Kindness—a celebration complete with gifts for over a thousand orphans in Soweto.
I was jet-lagged when I arrived, so at 7 o'clock the next morning, I chose not to get up and work out. Instead, I stayed in bed an extra hour to catch up on rest. That was my excuse the first day. By the third day, it was about the treadmill. I didn't like it. Not enough cushion support for my knees.
After three days of not exercising, my resolve to stay fit dissipates. It's easier to lie to myself: I'm too tired, too busy, there's not enough time are part of the downward spiral. Unfortunately for me, the resolve to work out is directly tied to eating healthfully.
The food at the hotel was not to my liking, so I made a special request for something simple that anyone can make: mashed potatoes. The chefs had no problem. And so I ate mashed potatoes and bread every night for the duration of my stay, ten days.
Ten days of high-glycemic foods combined with no workout equals ten extra pounds for me. Even worse than the weight gain was the way I felt. Exhausted. Lethargic. I felt aches and strains I didn't know existed. I knew for sure that this is what aging feels like. Aha! I got it. Working out slows the aging process and makes you more vital. Aha! Aha! Aha!
This is what Bob meant all those years—and why Jack La Lanne is a fitness idol at 91. When you nurture and support your body, it reciprocates. The basis of that support is exercise, like it or not. The most essential benefit is more energy. The bonus is weight control. Taking care of your body, no matter what your age, is an investment. The return is priceless.