100 Miles of Harmony W23: The Math Before the Menu
You don’t bonk at mile 70. You bonk somewhere around mile 30. You just don’t get the invoice until mile 70.
This is part of a series of posts regarding how we prepare, plan, and train to complete the 100-mile Ultramarathon Umstead 100. Our series for this event: 100 Miles of Harmony. For all the ultrarunning series, here, follow the link. Training for a 100. Alternatively, you can also follow last year’s series in our Podcast so you don’t miss the weekly summary post or our Album with a few songs with learning nuggets to prepare you for an ultra event.
That’s the thing nobody tells you about fueling an ultra. The failure is quiet and it’s early. By the time your legs go hollow and your brain starts negotiating with you about DNFs, the mistake is four hours old and there is no amount of Coke at the next aid station that undoes it. You cannot outrun an energy deficit. You can only refuse to build one.
So this week we’re not talking about what to eat. We’re talking about how much, and how often — because until you know the size of the hole, every food decision you make is a guess.
Two weeks from now we’ll build the menu: the tiered A / B / C / N system that tells you and your crew exactly what goes in your hand at any point in the race. But a menu without arithmetic is just a grocery list. The math comes first.
The Rule of Three
Everything in this block runs on three commitments. Keep them somewhere you’ll see them.
- Train the gut. Your stomach is trainable tissue. It adapts to volume and frequency exactly like your legs adapt to mileage — slowly, and only if you ask it to, repeatedly.
- Run the numbers. Know what a run costs you before you start it.
- Have a fallback. Every primary plan fails eventually. We build the fallback in Week 21.
This week is number two.
Assessment — What Does an Hour Actually Cost You?
Here’s the first thing to unlearn: you don’t burn calories per hour. You burn them per mile.
That distinction sounds academic until you look at what it does to your fueling plan. An hour is a unit of time. Your body doesn’t care about time — it cares about the work of moving your mass over ground. Cover more ground in that hour and you spend more, full stop. Two runners can go out for exactly sixty minutes and one of them comes back down 650 calories while the other is down 450. Same hour. Different bill.
Which means effort sets the burn rate, and the burn rate should set your eating schedule. Not the clock. Not your appetite.
Run your own number
The working estimate for running is roughly 0.63 calories per pound of bodyweight, per mile — that’s net, above and beyond what you’d burn sitting on the couch. If you want the gross figure, use 0.75.
Calories per mile ≈ your bodyweight (lb) × 0.63
Do it now, on paper:
| Bodyweight | ≈ Cal/mile (net) | ≈ Cal/mile (gross) |
|---|---|---|
| 140 lb | 88 | 105 |
| 160 lb | 101 | 120 |
| 180 lb | 113 | 135 |
| 200 lb | 126 | 150 |
Terrain adds to this. Umstead’s bridle trails are runnable, but they are not flat, and rolling climbs cost more than the table admits. Round up, not down.
Now watch what pace does to it
Take a 160-pound runner at ~100 calories per mile:
| Pace | Miles in one hour | Calories that hour |
|---|---|---|
| 9:00 / mile | 6.7 | ~670 |
| 11:00 / mile | 5.5 | ~550 |
| 13:00 / mile | 4.6 | ~460 |
Same sixty minutes. A 210-calorie spread between the top and the bottom. Over a four-hour long run, that gap is more than 800 calories — an entire meal you either accounted for or didn’t.
This is why “eat every 45 minutes” is not a plan. It’s a plan for one specific effort level, and the moment you go harder, it quietly becomes the wrong plan.
The ceiling nobody mentions
Here’s the second half of the equation, and it’s the humbling half.
A trained gut absorbs somewhere in the neighborhood of 60–90 grams of carbohydrate per hour — about 240 to 360 calories. An untrained gut manages roughly half that. Push past your ceiling and the surplus doesn’t become energy; it sits in your stomach, sloshes, and eventually comes back up.
Put the two numbers side by side and the whole sport comes into focus: burning ~600 an hour, absorbing ~250 an hour. You are running a deficit of roughly 350 calories every hour, no matter how well you eat.
You are not going to break even. Nobody does. The entire game is managing the size of the gap — taking in enough to stretch your stored fuel across the distance instead of spending it all in the first quarter. (How that stored fuel actually works, and what a hundred-mile budget looks like on paper, is Week 20’s job. Today we’re staying at long-run scale.)
Which brings us to the only lever you control mid-run: frequency.
Planning — The Four Phases
Fueling isn’t a moment. It’s four of them, and every long run between now and April should rehearse all four.
Phase 1 — The Pre-Long-Run Ritual (the day before)
Boring is the entire point. One meal, repeated, until it’s invisible. Something you’ve eaten before a hundred good runs and zero bad ones. Mine is pasta with red sauce and it has been for years — not because it’s optimal, but because it’s known. The day before a long run is not a place for a new restaurant.
Phase 2 — The Pre-Run Protocol (morning of)
Same principle, higher stakes. Fixed timing, fixed food, fixed quantity. Oatmeal, almond butter, coffee. Ninety minutes before the alarm-to-door window. Written down, not remembered. If you find yourself improvising at 4:30 a.m., you’ve already introduced a variable you can’t control for.
Phase 3 — During the Run (this is the one)
Three steps, in order, every long run.
Step 1: Price the run before you start it. Distance × your calories-per-mile. A 20-miler for our 160-pound runner is roughly 2,000 calories. Write the number at the top of your log. It reframes the run from “a thing I’m doing” to “a bill I’m paying.”
Step 2: Set your interval by effort, not by habit.
| Effort | Burn rate | Take fuel every |
|---|---|---|
| Easy / conversational long run | ~450–500 cal/hr | 45–60 minutes |
| Steady, marathon-effort, or hilly and honest | ~600+ cal/hr | 30–40 minutes |
Faster pace, rolling terrain, heat, wind — all of it pushes the spend rate up, and the interval has to tighten to match. This is the single most useful thing in this post: when the effort goes up, the gap between feedings comes down. Most runners do the opposite. They go harder, breathing gets heavier, eating gets less appealing, and they stretch the interval right when they should be shrinking it.
On race day at Umstead, default to the tighter end early. You will never regret calories you took in during the first loop.
Step 3: Stack the drink underneath. A gel is 100 calories. Chews run 90 to 180. That alone won’t reach 250 an hour at a 45-minute interval — the math doesn’t close. So it doesn’t have to close on solids alone:
- Drink calories, continuous: 100–200 cal/hour from a mix you sip on a schedule
- Solid or gel, on the interval: 100–150 calories each time the timer goes
Together: 200–350 calories an hour. That’s the target band. Below 200 you’re overdrawing. Above 350 you’re gambling with your stomach.
And set an actual timer/alarm based on the miles. Or if you are planning to hold a steady planned effort you can convert into a time range to use. Watch alert, on repeat, non-negotiable. Because the appetite signal is a lagging indicator — the first time you feel hungry on a long run, you are already thirty to forty minutes behind. You eat on the schedule whether you want to or not. Especially when you don’t want to.
One new item per run. Maximum. If you introduce three things and your gut turns, you’ve learned nothing — you now have three suspects and no verdict. One variable, logged, every time. Those logs are the raw material for Week 21’s lists.
Phase 4 — The Golden Hour (after)
The window in the first 30 to 60 minutes post-run is where the adaptation gets banked. Have the shake made, the meal ready, the whole thing decided before you left the house. If recovery requires a decision from a depleted brain, recovery doesn’t happen.
Your action items this week
- Calculate your calories-per-mile. One number. Write it on the first page of your training log.
- Price every long run before you run it — distance × cal/mile, logged in advance.
- Set the timer on your watch. Match the interval to the effort, not the habit.
- Hit 200–350 cal/hour, split between continuous drink and interval solids. Use your numbers.
- One new item per long run, and log what it did to you — good, bad, or neutral.
- Have the recovery meal made before you walk out the door.
Diabetes Learning Notes — Every Calorie Is Two Numbers
For those of us running with Type 1, this week’s math has a second column running alongside it, and it changes everything.
Every calorie is simultaneously an energy input and a glucose event. Non-diabetic runners get to think about one number. We think about two, at the same time, for eighteen straight hours. That’s not a burden — it’s the second discipline, and it’s a skill that compounds.
The per-mile insight cuts twice. If a faster hour burns 200 more calories, it’s also pulling glucose out of your bloodstream faster. The insulin sensitivity that made sense at conversational effort does not hold at marathon effort. The interval that keeps a non-diabetic runner fed is the same interval that keeps you out of a low — but your margin for error is thinner, and the correction has to come sooner.
Build the extra columns now. Every item you test in Phase 3 gets logged with three additional fields:
- Carb count (grams)
- Observed BG impact — how fast, how high, how long
- Insulin strategy — what you did, and whether it worked
Do that for the next twenty weeks and you won’t own a fueling plan. You’ll own a glycemic model of yourself.
Make the Pre-Run Protocol a mission checklist. Target BG before you start, basal adjustment and when you make it, breakfast-to-insulin timing. Same numbers, same sequence, every long run, until it runs without conscious thought.
Practice the branch, not just the plan. During the run, the schedule becomes conditional:
- BG 140 and stable → half a gel, hold the interval.
- BG 95 and trending down → full gel now, re-check in 15.
- BG climbing at hour three → hold the solid, take the drink only.
Rehearse those branches until they’re reflex, because you will be executing them at 2 a.m. with a brain that’s been awake for twenty hours.
And the Golden Hour is longer for us. Post-exercise insulin sensitivity can run for hours after you stop moving, which is exactly when it stops being top of mind. The run doesn’t end when you stop the watch. It ends when your glucose has been stable for hours.
The Live Lab — City of Oaks, Next Sunday
City of Oaks Marathon — Raleigh — Sunday, November 1. One week out.
If you’re on that start line, you’ve just been handed something a training run can’t give you: a real course, real aid stations, real race-day nerves, and a pace meaningfully faster than your long-run effort. Which makes it the perfect place to test the exact claim this post makes.
Price the marathon before you start it. Set your interval to the race effort — the tighter band, 30 to 40 minutes — and hold it even when the pace makes eating feel like a chore. Then log everything: what went in, when, and how your stomach answered. Twenty-six miles at race effort will teach you more about your fueling ceiling than a month of comfortable long runs. Come back with data. We’re going to use it.
Next week, Week 22: running in the dark. Umstead doesn’t end at sunset, and neither does your training. Then in two weeks, the menu — the A-List, B-List, C-List, and N-List that turn all of this math into something you and your crew can actually hand each other at mile 80.
Know the number. Set the timer. Eat before you’re hungry.
This Week’s Actual Numbers
| Week 23 | Mon | Tue | Wed | Thu | Fri | Sat | Sun | Total |
| Plan | Stretches & Rolling | 3 | 5 | 6 | Rest | 13 | 18 | 45 |
| Actual | Stretches | 4 | 8 | Rest | Rest | 20 | 10 | 42 |
Next Week Plan: City of Oaks Marathon
| Week 22 | Mon | Tue | Wed | Thu | Fri | Sat | Sun | Total |
| Plan | Stretches & Rolling | 3 | 5 | 6 | Rest | Rest | 26 | 40 |