Ultra Marathon Nutrition
& Fueling Strategy
Master your nutrition to conquer any distance — from training to race day.
Training, gear, and mental prep get all the attention — but nutrition is the fourth discipline of ultra running, and it's where most races are won or lost. You can train perfectly, have the best gear, and still DNF at mile 60 because your gut shut down.
Personalized Fueling Calculator
Enter your race details to get your per-hour targets for calories, carbs, fluids, and sodium.
Personalized Nutrition Calculator
Get your per-hour fueling targets based on your race profile.
Nutrition Fundamentals
The science behind what fuels your body through 100 miles.
Carbohydrates
Primary fuel source
- →Glycogen stores hold only ~2,000 calories — enough for ~2 hours at race pace
- →Target 30–90g of carbs per hour (train your gut to reach the higher end)
- →Use multiple carb types: maltodextrin + fructose absorbed via different pathways
- →Carb load 3–4 days before race: 8–10g per kg body weight per day
- →Start fueling within the first 30 minutes — not when you feel you need it
Hydration & Electrolytes
More critical than calories
- →Baseline: 16–24oz (500–750ml) per hour; increase in heat
- →Sodium: 300–700mg per hour — the most critical electrolyte
- →Hyponatremia (low sodium from over-hydration) is more dangerous than dehydration
- →Sweat rate test: weigh before and after a 1-hour run to calibrate
- →Urine should be pale yellow — not clear (over-hydrated) or dark (dehydrated)
Protein & Fat
Supporting roles
- →Fat is your aerobic engine for easy paces — but can't fuel high-intensity surges
- →Protein matters after mile 30+ in 100-milers: 10–20g/hour prevents muscle breakdown
- →BCAAs have limited evidence — whole protein sources are superior
- →Fat adaptation has merit in training but isn't a replacement for race-day carbs
- →Real food (potatoes, PB&J, broth) provides protein + fat naturally in later miles
Energy Gels
The backbone of ultra marathon fueling
Gels are the most reliable calorie delivery system in ultra running. Fast-absorbing, compact, and consistent — when your stomach gets finicky, gels often stay down when food won't.
Maurten
Gel 100
$3.00/gel
Best for
Pros
- +Hydrogel technology dramatically reduces GI distress
- +No fructose — easier on the gut than most gels
- +Thin, water-like texture goes down easily
Cons
- −Most expensive gel on the market
- −Neutral taste isn't for everyone
- −Lower calories than some alternatives
GU
Energy Gel
$1.30/gel
Best for
Pros
- +Most popular ultra gel for a reason — consistent and reliable
- +Huge flavor selection (30+ flavors)
- +Multiple caffeine levels to choose from
Cons
- −Higher osmolality can cause GI issues
- −Thicker texture is hard to take without water
- −Maltodextrin base isn't ideal for sensitive stomachs
Spring Energy
Energy Gels
$2.50/gel
Best for
Pros
- +Real whole food ingredients — oats, fruit, almond butter
- +Highest calories per gel in the category
- +Genuinely tastes like food, not a supplement
Cons
- −Thick consistency — needs practice
- −Refrigeration recommended for storage
- −Limited caffeine options
Huma
Chia Energy Gel
$2.20/gel
Best for
Pros
- +Real fruit + chia seeds — no artificial ingredients
- +Lower osmolality than most gels = gentler on stomach
- +Excellent flavor variety (all taste like real fruit)
Cons
- −Chia texture isn't for everyone
- −Lower calorie density requires more volume
- −Shorter shelf life than synthetic gels
Science in Sport
Beta Fuel Gel
$2.50/gel
Best for
Pros
- +40g carbs per gel — highest in class for serious fueling
- +2:1 maltodextrin:fructose ratio optimizes absorption
- +150 calories lets you fuel with fewer gels
Cons
- −High carb load can overwhelm untrained gut
- −Requires gut training to use effectively
- −Thick, dense texture
Energy Chews & Waffles
When gels get old, chewables keep you going
Chews and waffles provide the mental satisfaction of chewing — critical when gel fatigue sets in at mile 50. Many ultra runners use chews as their primary fuel for variety.
CLIF
BLOKS Energy Chews
$2.40/pack
Best for
Pros
- +Electrolyte-loaded options (Mountain Berry has 3× sodium)
- +200 calories per pack is solid density
- +Satisfying chew texture — prevents gel fatigue
Cons
- −Sticky in warm weather — can be hard to handle
- −May be too sweet late in races
- −Difficult to eat while running at faster paces
Skratch Labs
Sport Chews
$2.50/pack
Best for
Pros
- +Real fruit ingredients — genuinely tastes like candy
- +Non-GMO, clean label
- +Lighter on the stomach than most chews
Cons
- −Lower calorie density requires more volume
- −No caffeine option
- −Higher price for fewer calories
Honey Stinger
Organic Chews
$2.00/pack
Best for
Pros
- +Honey-based energy is natural and effective
- +Certified organic ingredients
- +Most affordable chews in category
Cons
- −Honey can crystallize in cold weather
- −Lower sodium than some competitors
- −Some find them too sweet late in a race
Honey Stinger
Stroopwafel
$1.50/waffle
Best for
Pros
- +Warm-waffle texture is uniquely satisfying mid-race
- +Solid enough to eat without hands (tuck in bra/pocket briefly)
- +Much easier to stomach than gels after hour 4
Cons
- −Gets soggy if wet
- −Hard to eat at faster running paces
- −Not ideal for the first hours of racing (slower digestion)
Hydration & Drink Mixes
Your liquid calorie and electrolyte foundation
Drink mixes let you absorb calories and electrolytes simultaneously while hydrating. For sensitive stomachs, liquid nutrition often works when solids don't.
Tailwind
Endurance Fuel
$40 / 30 servings
Best for
Pros
- +All-in-one: calories + electrolytes + hydration in one product
- +Dissolves completely — no sediment or sludge
- +Among the gentlest on the GI system available
Cons
- −Sweet taste becomes difficult late in long races
- −200 cal/serving isn't enough alone for high-intensity efforts
- −Requires precise measurement for ideal concentration
Skratch Labs
Sport Hydration
$22 / 20 servings
Best for
Pros
- +Real fruit flavors — actually enjoyable to drink all day
- +Higher sodium than most drink mixes (380mg)
- +Lower sugar won't cause energy spikes
Cons
- −Lower calorie density requires pairing with other fuel
- −No caffeine option
- −More expensive per calorie than Tailwind
Maurten
Drink Mix 320
$45 / 14 servings
Best for
Pros
- +Hydrogel technology dramatically reduces GI distress at high carb intakes
- +320 calories per serving is the highest in category
- +Neutral flavor doesn't cause taste fatigue
Cons
- −Significant investment at $45 for 14 servings
- −High carb load requires extensive gut training
- −Requires precise water measurement
Nuun
Sport Tablets
$7 / 10 tablets
Best for
Pros
- +Ultra-portable — fits anywhere
- +Effervescent tablets are easy and fun
- +Excellent electrolyte profile at low calories
Cons
- −Not a calorie source — must pair with other fuel
- −Dissolves slowly in cold water
- −Carbonation can cause bloating
Electrolyte Supplements
Prevent cramps, hyponatremia, and performance decline
Electrolytes are the most underrated tool in ultra nutrition. Most DNFs involving cramping or stomach issues are electrolyte failures. Get this right before anything else.
SaltStick
FastChews
$10 / 60 chews
Best for
Pros
- +Chewable format is easier than pills at mile 70
- +Balanced electrolyte profile (Na, K, Ca, Mg)
- +Fast-acting — dissolves quickly in mouth
Cons
- −Small individual dose requires multiple per hour
- −Tums-like texture isn't for everyone
- −Mild flavor may not appeal to all
SaltStick
Caps
$15 / 100 caps
Best for
Pros
- +Most comprehensive electrolyte capsule — all 5 electrolytes
- +215mg sodium per cap lets you precisely hit targets
- +Easy to carry — fits in any pocket
Cons
- −Harder to swallow while running than chews
- −Capsule breakdown can be inconsistent with some stomachs
LMNT
Electrolyte Drink Mix
$45 / 30 sticks
Best for
Pros
- +1000mg sodium per serving — designed for heavy sweaters
- +Zero sugar lets you pair with any calorie source
- +Excellent flavor despite high electrolyte content
Cons
- −Very high sodium isn't appropriate for everyone
- −Premium price
- −No calories means you still need calorie sources
Real Food Options
When gels fail, real food saves your race
After 10+ hours, synthetic products often become impossible to stomach. Real food — familiar, comforting, and varied — is what keeps many runners moving through the night.
Various
Medjool Dates
$0.25/date
Best for
Pros
- +Nature's gel — similar carb profile to energy gels
- +Rich in potassium (often depleted in long runs)
- +Incredibly affordable and available everywhere
Cons
- −Low sodium — combine with salt supplementation
- −Sticky in hot weather
- −Short shelf life once unpacked
Various
Baby Food Pouches
$1.00/pouch
Best for
Pros
- +Real fruit and vegetable ingredients
- +Same squeeze format as a gel — easy to use on the run
- +Gentler on the stomach than most synthetic products
Cons
- −Lower calorie density requires more volume
- −Limited flavors compared to sports products
- −Some runners find the idea off-putting
Justin's
Nut Butter Packets
$1.50/packet
Best for
Pros
- +High calorie density (190 cal in a small packet)
- +Fat + protein helps sustain energy in later miles
- +Savory profile is a welcome break from sweet
Cons
- −High fat slows digestion — not ideal early in race
- −Very thick — needs water to wash down
- −Minimal carbs for primary fueling
Aid Station Classic
Boiled Potatoes
Free (aid stations)
Best for
Pros
- +The most universally tolerated ultra fuel — available at most aid stations
- +Bland enough to eat when nothing else stays down
- +Warm salted potatoes provide sodium and comfort simultaneously
Cons
- −Low calorie density requires volume
- −Not available between aid stations
- −Can be hard to chew while running
Caffeine Products
Your night running secret weapon
Caffeine is the most evidence-based performance supplement in sports science. Properly timed, it reduces perceived effort, delays fatigue, and can turn a dying race around.
Generic
Caffeine Pills 200mg
$0.10/pill
Best for
Pros
- +Most affordable caffeine source by a large margin
- +Precise dosing — know exactly what you're taking
- +No stomach volume — adds no liquid or food bulk
Cons
- −No calories — purely caffeine, not fuel
- −Easy to accidentally overdose
- −Some runners dislike pills at night
Spring Energy
Canaberry (100mg caffeine)
$2.60/gel
Best for
Pros
- +Real coffee caffeine from Arabica beans
- +170 calories + 100mg caffeine in one product
- +Real food base means gentler on stomach than synthetic options
Cons
- −Most expensive caffeinated gel available
- −Thick consistency
- −Coffee flavor isn't for everyone
Tailwind
Rebuild Recovery
$35 / 15 servings
Best for
Pros
- +Complete protein + carbs in one product
- +Easy on the stomach when real food isn't appealing
- +Correct 3:1 carb:protein ratio for glycogen replenishment
Cons
- −Pricier than chocolate milk which achieves similar results
- −Some runners prefer whole food recovery
Fueling Strategy by Distance
Each distance requires a different approach. Here's what changes and why.
50K (31 miles)
200–300
Calories/hr
30–60g
Carbs/hr
16–24oz
Fluid/hr
300–500mg
Sodium/hr
Miles 0–10
Establish your fueling rhythm. 1 gel every 30–45 min. Don't wait until you're hungry.
Miles 10–20
Maintain gel/chew rotation. Start adding chews for variety. Consistent hydration.
Miles 20–31
Add caffeine if needed around mile 22–25. Push through with gels and chews. Finish strong.
~1,200–2,500 total calories | 6–10 gels equivalent
50 Miles
250–350
Calories/hr
40–70g
Carbs/hr
18–28oz
Fluid/hr
400–600mg
Sodium/hr
Hours 1–3
Gels, chews, drink mix. Establish rhythm. Don't go out too fast and burn glycogen.
Hours 3–6
Transition to real food at aid stations. Waffles, PB&J. Variety prevents flavor fatigue.
Hours 6–9
Anything that stays down. Caffeine at hour 6–7 if racing. Listen to cravings — they signal deficiencies.
Hour 9–finish
Survival fueling. Whatever you can get in. Broth if available. Caffeine for final push.
~2,500–4,500 total calories | Pack sweet and savory options
100K (62 miles)
200–400
Calories/hr
50–90g
Carbs/hr
20–32oz
Fluid/hr
500–700mg
Sodium/hr
Miles 0–20
Liquid nutrition dominant (Tailwind, Maurten). Gels for quick boosts. Establish hydration.
Miles 20–40
Add solid foods. Real food becomes important. Protein starts here (cheese, PB, bars).
Miles 40–55
Whatever stays down. Night sections: warm food preference. Caffeine timing critical.
Miles 55–62
Force minimum nutrition. 200 cal/hr minimum. Caffeine if needed. Finish line is close.
~3,000–6,000 total calories | Add protein after mile 30
100 Miles
200–350
Calories/hr
50–90g
Carbs/hr
20–30oz
Fluid/hr
500–1000mg
Sodium/hr
Miles 0–30 (Day)
250–350 cal/hr. Gels, chews, drink mix. Build a nutrition bank early while appetite is good.
Miles 30–60 (Evening)
Transition to real food. 200–300 cal/hr. Protein begins. Appetite often drops — don't fight it, just eat less more often.
Miles 60–80 (Night)
Warm foods: broth, quesadillas, soup. 150–250 cal/hr minimum. Strategic caffeine every 3–4 hours. Comfort foods matter psychologically.
Miles 80–100 (Dawn)
Reset: fresh food, fresh mindset. Caffeine boost at mile 80–85. 200+ cal/hr for the final push. Whatever it takes.
~5,000–9,000 total calories | Night sections are the biggest nutrition challenge
Common Mistakes & How to Fix Them
Most nutrition failures follow predictable patterns. Know them before they ruin your race.
Bonking (Energy Crash)
Causes
- ×Insufficient calorie intake
- ×Started fueling too late
- ×Went out too fast
Prevention
- +Start fueling within first 30 minutes
- +Set a timer — every 20–25 minutes
- +Never skip an aid station
Mid-Race Fix
- →Immediate 200+ calorie boost (gel + drink)
- →Slow down significantly while refueling
- →Walk if needed — you can recover from a bonk
Nausea & GI Distress
Causes
- ×Too much too fast
- ×Dehydration or overheating
- ×Products not trained with
Prevention
- +Test ALL products in training
- +Small, frequent intake vs. large boluses
- +Dilute your drink mix more than you think
Mid-Race Fix
- →Switch to bland foods (pretzels, bread, potato)
- →Ginger (ale, tea, chews)
- →Coca-Cola often works miraculously — try it
Hyponatremia (Low Sodium)
Causes
- ×Drinking too much plain water
- ×Insufficient sodium intake
- ×Heavy sweater ignoring electrolytes
Prevention
- +Never drink just water for extended periods
- +300–700mg sodium per hour minimum
- +Weigh yourself before/after long training runs
Mid-Race Fix
- →Increase sodium immediately (broth, pretzels, SaltStick)
- →Temporarily reduce fluid intake
- →Seek medical attention if confused or severely swollen
Flavor Fatigue
Causes
- ×Too many sweet products
- ×Same flavor for hours
- ×Loss of appetite from fatigue
Prevention
- +Pack both sweet AND savory options
- +Rotate flavors — at least 4 different tastes
- +Include real food from mile 30+ onward
Mid-Race Fix
- →Switch immediately to savory: broth, pretzels, chips, pickle juice
- →Try water instead of sweet drink
- →Cold soda (Sprite, Coke) can reset your palate
Dehydration
Causes
- ×Insufficient fluid intake
- ×Ignoring heat and sweat rate
- ×Over-relying on thirst sensation
Prevention
- +Drink 16–24oz per hour minimum
- +Monitor urine color (pale yellow target)
- +Pre-hydrate the days before your race
Mid-Race Fix
- →Gradual rehydration with electrolytes — not just water
- →Ice chips if feeling nauseous
- →Slow down at aid station for a full refill
Cramping
Causes
- ×Electrolyte depletion (especially sodium)
- ×Dehydration
- ×Going out too hard, too early
Prevention
- +Consistent sodium intake throughout the race
- +Don't ignore cramp warnings (twitching)
- +Pickle juice works — pack it in a small flask
Mid-Race Fix
- →Immediate electrolyte boost (SaltStick, LMNT, pickle juice)
- →Slow pace — let blood flow restore
- →Stretch if stopped, but don't force a severe cramp
Race Week Nutrition
The week before your race is where you build the fuel tank. Don't waste it.
7 Days Out
- →Normal eating — don't change anything dramatic
- →Begin hydration focus (extra 16oz/day)
- →Cut alcohol completely
- →Reduce fiber slightly
- →Avoid new or exotic foods
5 Days Out
- →Carb loading begins: 70–80% of calories from carbs
- →Target 8–10g carbs per kg body weight
- →Reduce fat to make room for carbs
- →Focus: pasta, rice, bread, oatmeal, potatoes
- →Hydration with electrolytes
3 Days Out
- →Continue carb loading
- →Cut fiber foods: no beans, cruciferous vegetables
- →Simple, familiar foods only
- →Hydrate with electrolytes every meal
- →Avoid excessive fruit (fiber + fructose)
Day Before
- →Normal-sized meals — don't stuff yourself
- →Biggest meal at lunch, not dinner
- →Light, familiar dinner (pasta, rice)
- →Hydrate throughout the day
- →Early bedtime — sleep > perfect nutrition
Race Morning
- →3–4 hrs before: 400–800 cal (bagel + PB + banana)
- →Same breakfast you've practiced — NO experiments
- →Sip electrolyte drink up to start
- →Last gel: 15–30 min before gun
- →Stop large solids 2 hrs before start
Aid Station Strategy
Aid stations are opportunities — most runners waste them. Here's how to use them efficiently.
What Most Aid Stations Offer
Efficient Aid Station Protocol
Caffeine Strategy
The most evidence-based performance tool available. Used correctly, it can turn a dying race around.
The Science
- →Reduces perceived exertion — effort feels easier
- →Delays central fatigue — brain gives up later
- →Effective dose: 3–6mg per kg body weight
- →Onset: 30–60 minutes after intake
- →Duration: 4–6 hours per dose
Timing by Distance
Mile 20–25 only
100–200mg total
Mile 30–35, then 42–45
200–400mg total
Mile 25–30, before nightfall, late-night
300–600mg total
Evening (mi 45), every 3–4 hrs through night, dawn (mi 80)
500–1000mg total
Warning: Don't start too early — save it for when you need it. Test all caffeine products in training.
Frequently Asked Questions
How much should I eat during an ultra?▾
When should I start fueling?▾
Can I fuel entirely from aid stations?▾
What if I can't stomach gels?▾
Should I take salt tablets?▾
How do I train my gut for higher carb intake?▾
How do I carb load properly?▾
Is it normal to feel nauseous during a 100-miler?▾
Is expensive nutrition worth it?▾
What's the best post-race recovery nutrition?▾
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