Thinking of running a marathon? Well, let me stop you right there. Don’t do it.

I’ve run 26 of these things myself (yes, 26!) so trust me — I get the appeal. I also understand, better than most, exactly what running 26.2 miles can do to you.

Here are 11 things the marathon has going against it.

Oh, finishing a marathon is on your bucket list? Guess who else’s bucket list includes that particular goal? Everyone’s. There are dozens of other and more original challenges out there. Find one.

As running author Jen Miller said last summer in The New York Times, “18 weeks of training and one marathon cost me more than $1,600.”

The cost adds up quicker than you’d think, starting with the entry fee, which can set you back $200 or more. Then there’s gear, nutrition, “training races,” travel costs, etc. For what you’ll spend on a marathon you could buy a pretty sweet road bike with enough left over for a helmet and a little bell for the handlebars.

No, really. I won’t get into the minutiae here, but running 26.2 miles truly does tear your body down. An older, wiser colleague — one who’s run tons of marathons and is quite medically literate — once confided in me that, from a health perspective, the ideal approach is to train for marathons, but never to actually race in one.

By which I mean they’ll look and feel as if you’ve rubbed them with fine-grit sandpaper. Same for other sensitive body parts, where 26 miles of steady friction takes a painful toll — notably on the thighs and, uh, “bathing suit area.”

Your feet never gave you trouble during training, so they’ll be fine during the marathon, right? Ha! Not true. No matter how fancy your “moisture wicking” socks or how cushy your shoes are, by the time you reach the final miles of a marathon you’ll probably be dealing with blisters the size of gumdrops.

Yes, “runner’s trots” is really a thing. And yes, it’s just as unpleasant as it sounds.

And in a race of 26.2 miles, hitting the wall isn’t a matter of if, but when. The human body can store only enough energy (in the form of glycogen) to fuel about two hours of hard running. After that you’re on empty and the journey to the finish line is less a race and more a slog. You’ll want to quit — and you just might.

The minute you tell someone you’re training for a marathon (and if you can’t tell people, what’s the point?), you’re bound to hear one or more of these comments, or some variation of them: “Ya know, the first guy to do that died!” (That’s a myth, by the way.)

“Wow, I get tired just driving 26 miles!”

“How far is your marathon?”

Once you commit to a marathon-training plan, you can pretty much kiss your weekends goodbye. Even if you do join friends on the occasional Saturday night, you’ll find yourself saying goodnight around 8:00 p.m. Don’t drink too much — you’ve got your long run in the morning!

Sounds counterintuitive, right? But it’s not unusual for folks to put on a few pounds while training for a marathon, often because runners use it as an excuse to scarf up every dessert in sight.

Post-marathon funk is a little-discussed but very real phenomenon. Many runners are surprised to learn that once the euphoria of the finish line fades they’re left feeling listless and blue.

Convinced yet? No? You’re stubborn. That’ll serve you well in the marathon. Good luck!

Mark Remy is a writer-at-large for Runner’s World, founder of the humor website, and a veteran of 26 marathons. He lives in Portland, Oregon.