Fatigue is an inevitable part of the latter stages of an endurance event. Whilst physical fatigue can usually be kept at bay - to some extent at least - by taking on carbohydrate or caffeine to boost your energy levels, what happens when ‘flavour fatigue’ strikes?

You may recognise the feeling of growing tired of the same energy products that you’ve been consuming for hours on end. They’ve started to taste different and the thought of eating any more makes you feel physically ill, although the alternative is to not eat anything and risk underfueling.

Dare we say it, but you may have even gotten a little fed up of our products if you’ve raced for long enough. 😱

We explore this unwanted phenomenon in a bid to help you keep flavour fatigue at bay during your next race…

What causes flavour fatigue?

It turns out there’s a fancier name for flavour (or taste) fatigue in the broader scientific literature: Sensory-Specific Satiety (SSS).

According to researchers, SSS is a “phenomenon that promotes the specific hedonic devaluation of the sensory properties of food.”

In human speak, that basically means that food starts to taste less appealing.

The sensory receptors on your tongue that detect flavour can become less responsive to the stimulus with repeated consumption, leading to a blunted sensitivity to the specific taste.

While it’s mainly tied to time and the particular food consumed, it can also apply to other foods with similar elements, such as texture. This might explain why switching gel flavours or brands isn’t always a solution when flavour fatigue strikes.

It’s been proposed that SSS is an adaptive mechanism that derives from animals’ need to eat a varied diet to obtain all of the nutrients for survival. If one food source is in abundance and easily accessible, it’d be practical to stick to eating just that. But, the theory of SSS prevents species from doing so, as they would still need other nutrients than those provided from the single source.

When does flavour fatigue occur?

In athletes, taste preferences have been observed to change over the course of exercise. A 2021 study found that…

  • In the first 60 minutes of exercise in hot conditions, cyclists demonstrated higher carbohydrate and sweeter taste preferences
  • After the 60-minute mark, the athletes preferred saltier tasting products

The authors recommend that you try to notice when personal changes in taste preferences occur during your training sessions, as they could be impacted by numerous factors, including hydration status, sodium losses, gastrointestinal distress, environment and personal preference.

With hydration in mind, some athletes’ voluntary fluid intake has been impaired because they report experiencing flavour fatigue with the electrolytes in their fluids.

If you’re relying on your fluids for both your electrolytes and your fuel, you’re at risk of a ‘double-whammy’ of dehydration and underfueling when flavour fatigue strikes. In these situations, it’s worth considering switching to more solid fuel sources, such as gels, chews and real foods, to ensure you’re not under-doing your carbohydrate intake because you’re drinking less.

Do certain types of foods make flavour fatigue better/worse?

A perfect example of flavour fatigue from our Athlete Case Studies database was when ultra runner Sophie Power experienced the phenomenon at the IAU 24-hour European Championships. She’d planned ahead to vary the taste and texture of her fuel sources, and this worked for nearly 20 hours. However, in the last four hours, she struggled to keep her carb intake high, as the flavour fatigue kicked in. She noted the only thing that sounded appetizing was custard!

We’ve also observed some athletes vary their intake more than usual during training to save their favourite flavours for race day. While it’s important to practise what you’ll be using ahead of time, allowing for variation (swapping a gel for a chew, or a mint for a lemon) in the weeks leading up to the big day isn’t a terrible idea.

It’s important to test different fueling formats in training to see which you prefer, as how much you like the fuel product can impact how much of it you’re able to consume. Common sense would lead us to believe that an item you deem more palatable in the first place would be less impacted by flavour fatigue. For example, a beverage with a higher palatability led to increased voluntary fluid intake over the course of three hours of exercise when compared to plain water.

A 2005 study suggests that ‘perceived pleasantness’ is related to physiological usefulness, although this doesn’t necessarily mean a pleasant food is immune to SSS. Sensory-related attributes, such as smell, taste, texture and sight or shape of foods, can play a part. So can other factors, such as cultural and social preferences.

Studies have also used "iso-caloric stimuli" (different stimuli but same total calories to eliminate confounding variables) that vary in sensory attributes, non-caloric stimuli (using calorie-free items) and even “sham feedings” where participants chew the food but do not swallow it. All of them still demonstrated SSS.

So, what does this all mean for you?

How to overcome flavour fatigue

Taking a mind over matter approach and trying to crack on with the same fuel when flavour fatigue hits may not be feasible, especially if your GI system is on the fritz and sucking down a gel leads you to feeling as though you want to vomit.

On the other hand, not taking fuel for an extended period of time could cause a host of other issues, ultimately leading to the dreaded DNF (Did Not Finish).

There isn’t always a straightforward, linear reason as to why one item feels inedible compared to another during an endurance event. The good thing is, SSS can dissipate over time, and your tastebuds can recover.

It’s unclear which variables impact the length of time it takes to experience flavour fatigue, but there are steps you can take to limit and overcome its effects…

  1. Anticipate it. If you know flavour fatigue is a possibility, you can make sure you have back-up fuel sources (e.g. chews, real foods like bananas) instead of being left to choose between bonking and force-feeding.
  2. Notice personal changes. Keep a log of when SSS happens to you during training, as you might be able to detect patterns. Note factors like weather, hydration status, exercise duration and intensity, as well as item texture and starting palatability.
  3. Get creative. Alter the other sensory elements of your source instead of just the general flavour. Play with texture, temperature, sight and smell to see if this makes a difference. For example, if you rely on your drinks for fuel, try gels (or vice versa).

Ultimately, the goal is to fuel. Endurance sports involve enough physical fatigue, so don’t let flavour fatigue be the one that takes you out of the game.

Further Reading