When you give a machine (like cars, computers, human bodies) no input, they will soon be operating at a deficit. It’s laughably obvious that they won’t function for very long or efficiently in a beneath-baseline state. The car engine stops working and you have to pull over, the computer turns off and you hope you’ve saved your work.

Bodies are more complicated. All the systems work together to try and keep on no matter how badly they’re treated. I’ve been running on some kind of deficit for at least thirty years either because I didn’t input anything or input too much of the wrong thing and then felt the urgent need to get rid of it.

I’m currently in training for an event that represents the longest and most difficult running I’ve ever done. Last year, I volunteered at a three-day, sixty-mile trail run last year and experienced such openness, warmth, and generosity that I wanted to be a participant. Getting ready has meant a lot of obvious “firsts” like distance, vertical gain, hours on the trail, days in a row. But it has also revealed an unknown depth to the fear I hold around eating and running.

In order to cover the distances and the elevation gain at the altitude we will be doing at the event, I have absolutely no choice but to eat and drink on the trail. This is brand new because I have never before fueled on runs. I have spent many years and miles trying to burn off what I had eaten, so why would I replace any of it?

Lack of input explains why a half marathon was my previous limit; two hours is when my glycogen stores run out. It also explains why a ten mile run would leave me pretty wrecked for the rest of the day. But for me, that depletion was saintly; it was the state that I craved because it quieted all the voices that said to get up, to do more. That too many drinks and too much food had to be compensated for.

But now, I had to eat before and during the run and drink liters of water while on the trail because I simply wouldn’t make it any other way. It was awkward and scary and I hated it because it meant that the state of nirvana - the used up, starving, depleted one - wasn’t going to be there at the end of the run. It meant there was no guarantee that I would feel I had done enough even when I was finished with the distance set for that day.

On the longest run I’ve ever done, a four hour trail around a beautiful canyon rim in the Utah wilderness, it became crystal clear that my self-imposed deficit ran deeper than sufficient food and water. I had spent so many days trying to run my way out of the canyon created by alcohol- or sugar-fueled hangovers. I had spent so much time clawing my way back to “better” - but actually, to a nebulous place of “not shameful.” I allowed all kinds of external sources to define what that was and it had often to do with the circumference of my thighs and the flatness of my belly. That possession of those things would mean an invitation to groups I wasn’t currently sufficient to occupy.

My mental landscape had been operating in whiteout conditions (and not the good, powder-day kind of way). So I ran to try and fix that. I kept performing the experiment despite the lack of results. I was a poor but persistent scientist. But running out of a canyon is the hardest possible way to exit. You have to go around, it’s longer, you’re more likely to get lost. It’s far easier to climb, and even better to not get stuck down there in the first place.

The change began with a few nuts. I chewed them into a paste that made me thirsty, which was a welcome change from the cringing, disgusted face I had previously made before drinking water while running. Two miles later it was a few bites of a Clif bar. Then a fruit leather. Then a liter and a half of water in tiny sips, and then two liters. I tried not to add up the calories.

At the end, I was sore and tired of course. But after getting back to camp and having something more substantial to eat, we went for a scenic drive. The boys and I did a bit of rock scrambling in the afternoon. I needed a nap but I didn’t feel like I was at the bottom of that canyon.

Because I ate and I walked and I ran slow, and because I stopped to take pictures when it was pretty, I made it without destroying the next few days.

It worked.

So did my body. It worked. It had enough juice to see clearly enough not to trip on the rocky trail. My body trusted me more because I was caring for it (even though I was treating it only slightly better than a pet). It got me through – sore and used – but I made it.

Now I know something I didn’t used to. Input is crucial to making a machine work, whether a car or a woodstove or a body. When our cars run out of gas, we go get more gas. We don’t get angry and scream at them for not functioning. There’s an assumption about proper input that we don’t give our human machines.

This body, the one I’ve hated and mistrusted and treated more poorly than anything else I’ve ever owned – it still worked, and it worked well. It did what I asked despite the deep muscle aches and overused tendons. It kept me upright on rocky, uneven terrain. It took me to the end.

If that isn’t unconditional love, I don’t know what is.

The race won’t happen for another few months but it’s purpose is, in many ways, already fulfilled. At the end of the canyon trail I made a promise: to remember that deficit is no longer a solid foundation. I can’t get out of the canyon by running, so I will work to keep myself from getting down there in the first place. I won’t always be able to fulfill it, but I will try.

I’ll try, body. Next time I’m in the shower I will thank you, dimply thighs, for what you did that day and all the others. You have the kind of strength that keeps going even after the deep hurt has set in.

So do I. It’s why I can carry the weight of all the aches and the terrible choices and the mistakes. And why I can recognize what it is to be forgiven (if only for a few hours) by such an important part of myself.