Real Food vs Gels: Build an Ultra Fueling Plan That Works

Real food vs gels for ultra racing: gastric emptying, carb ceilings, and a fueling plan by race duration. Build a gut that holds up on trail race day.

The real food vs gels argument gets framed as a moral question, with gels cast as industrial and boiled potatoes as honest. That framing has cost a lot of runners a lot of finishes. Both work. Both fail. What decides it is not which one is purer, it is gastric emptying rate, carbohydrate density, how many hours you have been running, and whether you can still stand the taste of the thing you are holding. This guide gives you a fueling plan built around when each format actually works, rather than around which camp you belong to.

What the research says about carbohydrate, not format

Start with the number that matters. In single-stage ultra-trail races, higher carbohydrate intakes around 120 g per hour were associated with reduced exercise-induced muscle damage and better recovery of running capacity 24 hours later, though 65 to 82% of athletes across the reviewed studies reported gastrointestinal symptoms (Arribalzaga et al., 2021).

Two things follow from that. Carbohydrate quantity drives performance more than carbohydrate source does. And GI trouble in ultras is close to universal, so the goal is managing it rather than avoiding it.

Absorption is the ceiling. Glucose alone tops out near 60 g per hour because of transporter saturation, but combining glucose with fructose raises the ceiling to roughly 90 g per hour and beyond (Jeukendrup, 2014). That ratio matters far more than whether the carbohydrate arrives as maltodextrin or mashed potato.

Why GI distress happens

Running reduces blood flow to the gut, slows gastric emptying, and compromises intestinal barrier function, a set of effects grouped under exercise-induced gastrointestinal syndrome (Costa et al., 2017). Add mechanical jostling, dehydration, and heat, and the gut becomes the limiting organ.

Nothing you eat causes this on its own. What food choice changes is how much additional stress you add on top.

Real food vs gels: the honest comparison

Gels and drinks

  • Carbohydrate density: 20 to 30 g per gel, in about 30 to 40 ml
  • Gastric emptying: fast, with liquids clearing at roughly 1.0 to 1.2 litres per hour
  • Glucose to fructose ratios are engineered, typically 1:0.8 or 2:1
  • Best window: hours 1 to 6, high intensity, hot conditions
  • Failure mode: flavour fatigue, and an osmotic load that pulls water into the gut if you take them without enough fluid

Solid food

  • Carbohydrate density: lower per gram, and it comes with fat, fibre, and protein that slow emptying
  • Gastric emptying: slower, and solids need more blood flow to digest
  • Best window: hour 6 onward, lower intensity, cooler conditions, long climbs and hiking sections
  • Practical ceiling: roughly 60 to 80 g per hour, so it is hard to hit 90 g/hr on solids alone
  • Failure mode: sitting undigested in your stomach when you pick the pace up

One detail runners miss: carbohydrate bars are statistically more likely to trigger GI symptoms than gels or drinks delivering the same carbohydrate, largely because of fibre and fat content. Solid does not automatically mean gentle.

The comparison that actually decides it

Intensity is the variable nobody talks about. At 85% of max heart rate, gut blood flow is low enough that solids are a bad bet regardless of preference. On a long hike-heavy climb at 65%, your gut can handle a sandwich comfortably.

So the answer changes across a single race. This is why the format debate is unresolvable in the abstract.

Building a fueling plan by race duration

Under 3 hours

Liquid and gels only. Target 60 to 90 g of carbohydrate per hour, taken as a drink mix plus gels. You will not be out there long enough for flavour fatigue and you are running hard enough that solids are a liability.

3 to 6 hours

Mostly gels and drink, with one or two solid items as a mental break. Target 60 to 90 g/hr.

A workable pattern: drink mix delivering 30 g/hr in the flask, one gel every 30 minutes, and something savoury around hour four to reset your palate.

6 to 12 hours

Now the balance shifts. Target 60 to 90 g/hr but expect to fall short in the later hours.

  • Hours 1 to 4: gels and drink, 80 to 90 g/hr
  • Hours 4 to 8: alternate gels with real food at aid stations, 70 to 80 g/hr
  • Hours 8 plus: whatever goes down, 50 to 70 g/hr

Over 12 hours

Real food becomes structural rather than optional. Nobody takes 40 gels across a 100 miler and finishes well.

  • Base layer: liquid carbohydrate you sip continuously
  • Aid stations: broth, potatoes, rice, quesadillas, whatever the race provides
  • Gels held in reserve for climbs and low points
  • Accept 50 to 70 g/hr and prioritise consistency over peak numbers

Our guide on hourly calorie needs for ultra trail running covers how to set those targets against your body mass and pace.

Foods that hold up on trails

Reliable savoury options: boiled salted potatoes, white rice balls, cheese quesadillas, pretzels, broth, ramen, crisps, plain white bread with jam.

Reliable sweet options: banana, dates, rice cakes with syrup, sweetened condensed milk in a flask, boiled sweets, cola.

Things that betray people: anything with high fat and fibre, protein bars, nuts in quantity, cured meats in heat, dried fruit beyond small amounts.

The pattern is consistent. Low fat, low fibre, low protein, mostly simple carbohydrate, plus salt. Boring and effective.

Gut training is the part people skip

Your gut adapts to what you ask of it. Regularly consuming carbohydrate during training increases intestinal transporter density and improves tolerance, which is why elite ultra runners can hold 90 g/hr while a recreational runner throws up at 60.

A simple progression across eight weeks:

  1. Weeks 1 to 2: 40 g/hr on every run over 90 minutes
  2. Weeks 3 to 4: 60 g/hr, introducing race-specific products
  3. Weeks 5 to 6: 75 g/hr on long runs, plus solid food at the same points your race has aid stations
  4. Weeks 7 to 8: full race simulation at target intake, at race pace, in race conditions

Practise eating on climbs and while moving. Sitting in a chair at an aid station is a different physiological test than chewing a potato while power hiking at 12% gradient.

Trailia generates fueling plans segment by segment against your course profile, so the carbohydrate target changes with the climb you are on. You can sanity-check the whole build with the Race Readiness tool before you commit to it.

Key takeaways

  • Carbohydrate quantity matters more than format, with 60 to 90 g/hr the useful working range
  • Use liquids and gels in hours 1 to 6 and at higher intensities, when gut blood flow is lowest
  • Bring in real food from hour 6 onward, and accept a lower carbohydrate ceiling of 60 to 80 g/hr
  • Bars are more likely to cause GI symptoms than gels at equal carbohydrate, so solid does not mean gentle
  • Train your gut across eight weeks rather than testing new food on race day

Where to go from here

Stop asking which is better and start asking which is better right now, at this intensity, at this hour, in this heat. Write a plan that changes format as the race goes on, rehearse it on long runs that mirror the terrain, and carry one backup option you know you can stomach when everything else tastes wrong.

Trailia builds that plan against your actual course, matching carbohydrate targets and formats to each segment rather than handing you a single number for the whole day.

Citations

  • Arribalzaga, S., Viribay, A., Calleja-Gonzalez, J., Fernandez-Lazaro, D., Castaneda-Babarro, A., & Mielgo-Ayuso, J. (2021). Relationship of Carbohydrate Intake during a Single-Stage One-Day Ultra-Trail Race with Fatigue Outcomes and Gastrointestinal Problems: A Systematic Review. International Journal of Environmental Research and Public Health, 18(11), 5737.
  • Jeukendrup, A. E. (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Medicine, 44(Suppl 1), S25-S33.
  • Costa, R. J. S., Snipe, R. M. J., Kitic, C. M., & Gibson, P. R. (2017). Systematic review: exercise-induced gastrointestinal syndrome, implications for health and intestinal disease. Alimentary Pharmacology & Therapeutics, 46(3), 246-265.
  • Pfeiffer, B., Stellingwerff, T., Hodgson, A. B., et al. (2012). Nutritional intake and gastrointestinal problems during competitive endurance events. Medicine & Science in Sports & Exercise, 44(2), 344-351.
  • Podlogar, T., & Wallis, G. A. (2022). New Horizons in Carbohydrate Research and Application for Endurance Athletes. Sports Medicine, 52(Suppl 1), 5-23.

Frequently Asked Questions

Is real food or gels better for ultramarathons?

Neither wins outright, because the right choice changes across a race. Gels and drinks clear the stomach faster and suit the first six hours and higher intensities, while real food works better from hour six onward when the pace drops. Most successful ultra fueling plans use both in sequence.

How many carbs per hour should I eat in a trail race?

Between 60 and 90 grams per hour is the working range for most trail runners, with research linking intakes near 120 g/hr to less muscle damage in single-stage ultras. Very few recreational runners tolerate the top end without dedicated gut training. Start at 60 g/hr and build up in training.

Why do gels upset my stomach?

Usually because they are taken without enough fluid, which leaves a concentrated sugar load pulling water into the gut. Running also reduces blood flow to the digestive system and slows gastric emptying, so the same gel that is fine at rest becomes a problem at pace. Take gels with water rather than sports drink.

Can I fuel an entire ultra on real food?

You can, but the carbohydrate ceiling is lower, roughly 60 to 80 grams per hour, because fat, fibre, and protein slow gastric emptying. That is workable for long, low-intensity races where you are hiking climbs. For faster races under six hours it will leave you underfuelled.

Are energy bars gentler on the stomach than gels?

No, and this surprises people. Carbohydrate bars are statistically more likely to trigger GI symptoms than gels or drinks delivering the same carbohydrate, mainly due to their fibre and fat content. Solid does not automatically mean easier to digest.

What real foods work best during a trail race?

Low fat, low fibre, mostly simple carbohydrate options with salt: boiled potatoes, white rice, quesadillas, pretzels, broth, banana, dates, and crisps. Avoid nuts in quantity, protein bars, and anything heavy in fat. The reliable choices are almost always boring.

How do I train my gut to handle more carbohydrate?

Consume carbohydrate on every run over 90 minutes and increase the hourly amount gradually across about eight weeks. Start near 40 g/hr, build to 75 g/hr on long runs, then run a full race simulation at target intake. Regular carbohydrate intake during training increases intestinal transporter density and tolerance.

Does intensity change what I should eat?

Substantially. At high intensity, gut blood flow drops and solid food sits undigested, so liquids and gels are the safer choice. On long hiking climbs at lower intensity your stomach can handle real food comfortably. Match the format to the effort, not just to the clock.

Why does everything taste wrong late in an ultra?

Flavour fatigue is real and it hits sweet products hardest, which is why savoury options become valuable after hour six. Carrying one salty backup you know you can stomach is worth more than an extra gel. Broth and salted potatoes rescue a lot of races.

Should I use glucose and fructose mixes?

Yes, if you want to exceed roughly 60 grams per hour. Glucose alone saturates its intestinal transporter near that level, while adding fructose uses a separate pathway and raises the ceiling to around 90 g/hr. Most modern sports products are already formulated with this ratio.