Don't necessarily do as I've done here--I'm just illustrating a point.
For my three fastest marathon times, I've eaten as the last meal before:
- 3:32 - cheap mediocre Mexican food.
- 3:39 - Mexican in Florence, KY on the way to Cincinnati and pub grub at Nicholson's in Cincinnati.
- 3:49 - pub food in Memphis. (I figured it was a better option than BBQ)
There are multiple reasons why I do this:
1) After running the 3:39, I've sort of become superstitious about what I eat the day before.
2) I've never had any decent luck getting near an Italian place while out of town, the night before a marathon.
3) I run long runs on Saturday, which means that fish frys and team lunches at the Mexican place down the road are pretty common day before meals. They haven't let me down.
Food before my worst marathon times:
1) 4:42 - don't recall, but was on the road, so we probably tried to find pasta, especially since my daughter will mostly only eat that.
2) 4:34 - first marathon, spaghetti
3) 4:31 - pasta (it was a hilly marathon and I was coming off of injury)
DNF - ate pasta due to having an iffy stomach all week. For me, apparently, iffy stomachs need a little bit of grease, not carbs.
I'm not saying the night meal before doesn't matter. However, what you eat the night before is more likely to harm your performance than help it if you haven't gotten your body used to it before then.
You presumably spent 12-18 weeks preparing for this marathon. The body changes didn't happen overnight. Why magically change your diet the night before?
- Eat what you know works for your long runs, even if it violates conventional running wisdom.
- Don't eat too much.
- Don't eat too little.
- Eat your last meal the same amount of time before your race as you do before your long runs.
- Hydrate adequately.