What to Eat During a 50K Ultra: A Real-World Fueling Guide

A 50K is where a lot of runners find out their marathon fueling plan wasn't actually a fueling plan. It was just "take a gel once in a while and hope for the best."

That can work for 26.2. Sometimes. A 50K is usually long enough that you need a real system, but still short enough that you probably don't need to treat it like a 100-miler with a grocery store in your vest.

My boring answer for most runners is gels first.

I prefer gels personally, and I think they're still the best backbone for a lot of 50K plans because they're easy to carry, easy to count, and a lot easier to standardize than grabbing random snacks off an aid-station table. Real food still has a place. But for most first-time 50K runners, it should be support, not the whole strategy.

A 50K is long enough to need a plan

During prolonged exercise, carb intake improves performance and helps delay the point where your pace and brain both start falling apart (Jeukendrup; Temesi et al.). The broad endurance-sport guidance is familiar by now: around 30-60 g/h for events lasting 1-2.5 hours, and up to 90 g/h for longer events if you're using multiple transportable carbohydrates like glucose plus fructose (Burke et al.; Thomas, Erdman, and Burke).

A 50K usually sits in the middle of that. Not short. Not all-day.

So for a lot of runners, the practical target looks more like this:

Runner profile	Practical carb target
Newer runner, sensitive stomach, 6-8+ hour day	45-55 g/h
Most trained 50K runners	55-70 g/h
Experienced runner with a well-trained gut	70-80+ g/h

That table is an inference from the endurance-carb literature, not some official 50K-only rule. I think that's the honest way to use the evidence.

And if you're a smaller runner, or a female athlete with lower absolute glycogen storage, you may hit the point where fueling matters sooner, not later. The number on paper might be a bit lower in absolute grams per hour, but the need for a plan is not lower.

Gels should usually be the backbone

Here's where I think people overcomplicate this.

A lot of runners hear "ultra" and immediately start picturing quesadillas, pickle juice, boiled potatoes, Coke, broth, candy, and a handful of pretzels stuffed into a race vest pocket like rocket appliances. Then they spend half the race trying to remember what they've actually eaten.

You need carbs you can count.

And when the trail gets ugly, do you really want to be guessing?

That's why gels, chews, and drink mix are still the simplest base. A gel is usually 20-30 g of carbs. A bottle of sports drink might add another 20-40 g, depending on the mix. That lets you build an actual hourly target instead of doing trail math with orange slices and vibes.

Real food helps for three reasons:

1. Taste fatigue
2. Texture variety
3. Aid-station practicality on longer trail days

But "real food" only helps if it still does the main job, which is getting digestible carbs into you without trashing your stomach.

So if you want the short version, here it is: build the plan around gels or drink mix, then use real food as a supporting actor.

What real food actually works

The best real foods in a 50K are usually the least exciting ones.

Think simple, low-fiber, low-fat, easy-to-chew carbs:

• banana halves
• boiled salted potatoes
• applesauce pouches
• white rice balls
• white bread with jam or honey
• low-fiber bars you've already tested
• flat Coke later in the race if you tolerate it

And the foods that get people into trouble are usually obvious in hindsight: nut-heavy bars, high-fiber energy balls, jerky when you're already dehydrated, giant peanut butter sandwiches, or whatever mystery baked good looked amazing at mile 18 and horrible at mile 22.

A recent 56 km trail ultramarathon study found that total FODMAP intake was not clearly tied to GI symptoms, but runners with more severe symptoms tended to have higher caffeine, fat, and some polyol intake patterns around the event (Convit et al.). So the useful takeaway isn't "all GI problems are FODMAPs." It's that piling on gut irritants is a great way to make a bad day worse.

If you already know you're FODMAP-sensitive, that's different. A low-FODMAP approach can help some athletes with recurring GI problems (Lis et al.). But for most runners, the simpler rule is enough: boring carbs win.

Need exact carb, fluid, and sodium targets for your next ultra? Build your personalized plan in about 60 seconds: Use the free EnduranceOS calculator.

What one hour can actually look like

This is the part most posts skip, and it's the part people actually need.

Here are a few workable examples.

Gel-first plan: one gel every 25-30 minutes plus water, which gets you around 50-60 g/h depending on brand.

Gel plus sports drink plan: one gel per hour plus one bottle of sports drink, which often lands around 50-70 g/h.

Gel plus real-food plan: one gel, half a banana, and some sports drink, which can still get you into the 45-65 g/h range without feeling like pure sugar all day.

Aid-station-supported plan: carry enough gels to cover the race if aid-station options go sideways, then use bananas, potatoes, or Coke as bonus carbs when they actually look good.

A sample 6-hour menu

Let's make this less abstract. Say you're targeting about 55-60 g/h for a six-hour 50K and you prefer gels.

Time	Fuel	Approx carbs
Start to 1:00	2 gels + water	50 g
1:00 to 2:00	1 gel + sports drink	55-60 g
2:00 to 3:00	2 gels + water	50 g
3:00 to 4:00	1 gel + half banana + sports drink	55-65 g
4:00 to 5:00	2 gels + water, maybe Coke late	50-60 g
5:00 to finish	1 gel + sports drink or Coke, whatever still sounds edible	40-60 g

That's not the only way to do it. It's just a good example of what a mostly-gel plan looks like when you add a little variety before your mouth starts filing complaints with management.

That's the big point. Carry backup carbs.

In one small trail-running study, athletes averaged only about 14.9 g/h of carbs during a 30 km event, way below current recommendations (Jimenez-Alfageme et al.). Small sample, yes. But it matches what you see in real life. A lot of trail runners underfuel because aid-station eating feels casual until the wheels come off.

Running is harsher on your gut than cycling

Even if you've handled big carb numbers on the bike, do not assume the same number will feel identical on the run.

Running tends to be rougher on the gut than cycling because of the mechanical bounce, and carbohydrate oxidation from drinks is lower during running than cycling at the same intake in lab settings (Pfeiffer et al.). So if your long-ride number is 90 g/h, that doesn't automatically mean your 50K number should be.

This is also why gut training matters so much. Your intestine adapts. Transporters adapt. Tolerance improves when you practice feeding at effort instead of treating race day like the first live rehearsal (Jeukendrup and McLaughlin).

If you haven't been practicing, read the gut training post before you try to force-feed yourself 80 g/h on race day.

Bad trade.

The GI mistakes that wreck 50Ks

The mistakes are usually boring. They're just expensive on race day.

Going too hard on real food too early. A small piece of banana is one thing. A full peanut butter wrap at hour two is another.

Stacking sugar without enough water. Gel plus sports drink plus chews all at once can turn your stomach into a panic room. If you're taking a gel, wash it down with water. If your sports drink is your carb source, stop stacking extra sugar on top for no reason. The GI problems post gets into this in more detail.

Waiting until you're hungry. Hunger is not a great fueling clock in a 50K. By the time food sounds good, you're often already behind.

Using aid stations as your whole plan. Aid stations are helpful. They are not your primary strategy. Brands change. Food runs out. Something looked good in the race email and looks disgusting on the day. Carry enough of your own fuel that an ugly aid station doesn't derail the race.

Too much caffeine too soon. Some caffeine can help. Too much can blow up your gut or leave you jittery and weird by mid-race. The caffeine timing post is worth reading if that's part of your plan.

Fluid and sodium still matter

A 50K fueling plan is not just food.

Fluid needs depend on sweat rate, weather, body size, and how exposed the course is. Plenty of runners will land around 400-800 mL/h, but hot weather and heavy sweating can push that higher. If you haven't done a sweat test, start with the sweat rate guide because guessing here gets sloppy fast.

Same for sodium. Some runners do fine around 300-600 mg/h. Others, especially salty sweaters or runners in the heat, may need more. The sodium post covers the math.

And no, more water is not always safer. Overdrinking is still the main driver of exercise-associated hyponatremia, especially in longer events and smaller athletes (Hew-Butler et al.). So the goal is enough fluid to stay functional, not a personal side quest to empty every cup at every aid station.

Here's what I'd actually tell most first-time 50K runners

Start with gels.

Seriously. Make them the base.

If you love potatoes, bananas, or Coke later in the race, great. Use them. But your default should still be something you can count when your brain departments are getting sketchy after four hours on trail.

So my default advice for a first 50K looks like this:

• Aim for 50-60 g/h unless you've trained higher.
• Start eating in the first 30-40 minutes, not when you feel tired.
• Use one gel every 25-30 minutes, or one gel plus sports drink if that sits better.
• Carry enough fuel to cover the whole race even if you plan to use aid stations.
• Use real food for variety, not as an excuse to underfuel.
• Practice the exact products on long runs and steady weekday sessions too, not just once every other weekend.
• If it's hot, back off the macho carb target a little, drink sensibly, and adjust sodium upward.

That's the sort of plan most runners can actually follow with dirty hands, a bouncing vest, and a brain that's slowly turning into mashed potatoes.

A good 50K plan should be boring enough to repeat

That's really the standard.

You do not need a genius ultra menu. You need a plan simple enough that you can still follow it when the course gets steep, your stomach gets picky, and the aid station looks like a yard sale of half-open snacks.

For most runners, that means gels as the base, a few real-food options for backup, and enough practice that none of it feels new when the race starts asking real questions.

If you want a cleaner starting point than guessing, the EnduranceOS planner will map out the carb, fluid, and sodium side for you in about 60 seconds.