When sweet fuel stops working.

You’re halfway through a long run. Your watch says you should eat again. You reach into your vest, pull out another gel… and suddenly the thought of swallowing it makes you feel sick.

Not hungry. Not under-fueled. Just completely done with sweet sports nutrition.

If this sounds familiar, you’re not alone.

Many runners experience nausea, stomach discomfort, sweetness fatigue, or a total loss of appetite during long endurance efforts, especially during trail runs, marathons, ultras, long rides, or hot summer sessions. And while energy gels absolutely have their place, they can become surprisingly difficult to tolerate after several hours of exercise.

The problem is often not just energy itself. It’s the ability to continue eating.

And during endurance sports, that changes everything.

Why Do Energy Gels Make Some Runners Feel Sick?

Energy gels are designed to deliver fast carbohydrates in an efficient format. For shorter or high-intensity efforts, they can work extremely well.

But during longer runs, several things start happening at once:

• digestion slows down

• blood flow moves away from the digestive system

• dehydration increases

• sweetness becomes overwhelming

• appetite begins to disappear

Suddenly, the same gel that tasted fine at kilometre 10, feels impossible at kilometre 45.

For some runners, this shows up as:

• nausea

• bloating

• reflux

• dry mouth

• stomach cramps

• gagging when trying to eat

• feeling “disgusted” by sweet fuel

It’s one of the most common endurance fueling problems - especially in trail running and ultra-distance events where athletes are eating for hours, not minutes.

And importantly, this doesn’t mean gels are “bad.”

It simply means the body and brain can struggle with repeated sweetness, and a lack of texture over long durations.

What Happens to Digestion During Long Runs?

During endurance exercise, your body prioritises movement over digestion.

Blood gets redirected toward working muscles and away from the digestive system. At the same time:

• breathing rate increases

• stress hormones rise

• hydration levels fluctuate

• core temperature climbs

Your gut suddenly has a much harder job to do.

This is one reason endurance fueling can feel very different during a race compared to eating normally at home.

A gel that works perfectly during a short training session might feel unbearable six hours into an ultra.

Trail running adds another layer too:

• heat

• altitude

• downhill impact

• technical terrain

• accumulated fatigue

All of these can make digestion more fragile.

This is why experienced endurance athletes often spend just as much time training their stomachs as they do training their legs.

Why Sweetness Becomes Harder to Tolerate After Hours of Running

This is the part most sports nutrition brands don’t talk about enough.

Sweetness fatigue is real.

After consuming sugary drinks, gels, chews, and energy products hour after hour, the brain often reaches a point where it simply doesn’t want any more sweetness.

Even if the body still desperately needs carbohydrates.

You see this constantly in endurance events:

• runners craving salty broth at aid stations

• cyclists reaching for bread instead of candy

• athletes suddenly obsessed with crisps, potatoes, soup, or rice

• even salted watermelon becomes a food of dreams with a refreshing texture and taste

The issue becomes psychological as much as biological.

Because fueling long efforts isn’t just physical - it becomes emotional too.  

Many runners recognise the moment instantly:

“I can’t face another gel.”

That’s often when fueling starts to fall apart.

The Difference Between Energy Needs and Appetite

One of the biggest misconceptions in sports nutrition is assuming hunger and fueling are the same thing.

They’re not.

During long endurance efforts, athletes often still need energy even when they no longer feel like eating.

That’s where problems begin.

If you stop fueling entirely because everything feels sickly sweet, energy levels can crash very quickly:

• pace drops

• focus disappears

• mood changes

• stomach problems worsen

• recovery becomes harder

This is why maintaining the desire to eat matters so much during endurance sports.

Not just hitting carb targets on paper.

Why Ultra Runners Often Crave Savoury Foods

Watch any ultra-marathon aid station after several hours and you’ll notice something interesting.

Athletes start reaching for:

• soup

• potatoes

• bread

• noodles

• cheese

• salty snacks

Not because they suddenly stopped needing carbohydrates.

But because savoury foods can feel psychologically easier to tolerate after long periods of sweetness.

This is one of the reasons many endurance athletes now mix sweet and savoury fuel sources during longer efforts - especially during ultras, gravel races, mountain adventures, and long training days.

Not because gels are “wrong.”

But because variety helps people keep eating consistently.

And consistency is what endurance fueling is really about.

How to Fuel Long Runs Without Destroying Your Stomach

There’s no perfect fueling strategy for everyone, but experienced endurance athletes often follow a few common principles:

Start eating early

Don’t wait until you feel empty. Small, consistent fueling is usually easier on the stomach, and allows time you to digest what you eat, before it's too late.

Train your gut & metabolism

Your digestive system and metabolism adapts over time just like your legs do. It can learn to cope with and use different fuel sources if you train it.

Use multiple textures and flavours

Changing between drinks, gels, soft foods, and savoury options can reduce flavor fatigue.

Don’t rely only on sweetness

Many athletes prefer a mix of sweet and savoury foods better over long durations.

Hydrate properly

Dehydration often makes stomach issues worse.

Slow down temporarily if needed

Sometimes intensity itself is the problem. If your stomach completely shuts down, reducing pace for a few minutes can help digestion recover.

You can also explore our guide to:

• homemade isotonic drinks

• why digestion matters in endurance performance

• real food sports nutrition

Mixing Sweet and Savoury Fuel During Endurance Efforts

One of the most effective approaches for long endurance days is combining different types of fuel rather than relying entirely on one flavour profile.

Some athletes use:

• gels during climbs or hard efforts

• drinks for quick carbohydrates

• bananas or rice cakes at aid stations

• savoury foods later in races when sweetness becomes difficult

This is one of the reasons products like Yanaa’s savoury pouches exist: to provide variety, real ingredients, and something easier to keep eating when sweetness becomes overwhelming.

Yanaa was never designed to replace every gel.

It’s designed as a savoury layer within your fueling system - something that helps maintain appetite, comfort, and consistency during long outdoor efforts.  

Because sometimes the wall isn’t your legs.

It’s your appetite.

Well,

Energy gels can be incredibly useful tools for endurance sports. But if they start making you feel sick during long runs, you’re far from the only one.

The longer the effort becomes, the more fueling shifts from pure performance science toward something more human:

• appetite

• comfort

• texture

• emotion

• variety

• the simple ability to keep eating

And sometimes, the smartest fueling strategy isn’t adding more sweetness.

It’s adding balance.

 

Frequently Asked Questions

Are energy gels bad for your stomach?

Not necessarily. Many athletes tolerate them very well, especially during shorter efforts. Problems usually appear during longer endurance sessions where digestion, dehydration, and sweetness fatigue accumulate.

Why do I feel nauseous during long runs?

Nausea during endurance exercise can come from several factors:

• reduced digestion

• dehydration

• overheating

• intensity

• repeated sugary fuel intake

• underfueling or overfueling

Should I stop using energy gels?

Not automatically. Many athletes benefit from combining gels with other fuel sources rather than removing them completely.

What can I eat instead of gels while running?

Popular alternatives include:

• bananas

• rice cakes

• potatoes

• energy bars

• isotonic drinks

• savoury purées

• soft real-food options

Why do ultra runners eat salty foods?

After several hours of exercise, many runners experience sweetness fatigue and naturally crave savoury flavours, broth, potatoes, or salty snacks.

Can savoury foods help during endurance sports?

For many athletes, yes. Savoury foods can provide variety, reduce flavour fatigue, and help maintain the desire to keep eating during long efforts.