Most people treat energy gels like a fire extinguisher: kept sealed, saved for the emergency, cracked open only on race day.

It sounds sensible — even frugal.

It is also the single most common reason gels backfire when they finally matter.

Where the myth comes from

The logic is understandable. Gels cost money, they are associated with racing, and “saving them for when it counts” feels disciplined. Underneath sits an assumption: that your stomach will simply do on race day whatever you ask of it. But race-day fuelling is not ordinary eating. It is concentrated carbohydrate, taken at speed, under heat and intensity that your everyday meals never involved. Assuming your gut will handle that untested is the actual gamble.

Your gut learns like your muscles

This is the finding the myth ignores. The gastrointestinal tract responds to training the same way muscles do — it adapts to the demands you place on it regularly.^[1]

Increasing habitual carbohydrate intake raises the abundance and activity of the intestinal glucose transporter, SGLT1. One line of evidence suggests that shifting dietary carbohydrate from around 40% to 70% could roughly double SGLT1 transporter density over time.^[1] More transporters means more capacity to absorb carbohydrate during exercise.

It is not only absorption — it is comfort

In one study, trained runners repeatedly ingested a carbohydrate–electrolyte solution during 90-minute runs. Stomach comfort improved significantly across the trials — without a measurable change in how fast the stomach emptied.^[1] The gut had not sped up. It had learned to be comfortable.

This is why an athlete can tolerate on their tenth practised long run a fuelling load that made them miserable on the first. Nothing about the gel changed. The gut did.

How quickly does it work?

A controlled trial found that around two weeks of repeated carbohydrate gut-challenge reduced exercise-associated gastrointestinal symptoms and malabsorption in the participants studied.^[2] That was a small, non-athlete sample — treat the exact number as a signpost, not a guarantee.

The corollary is uncomfortable for the “save it for race day” crowd. If adaptation takes weeks of practice, then the athlete who opens their first gel at the start line has given their gut exactly zero of the preparation the evidence says it needs.

“Nothing new on race day” cuts both ways

Most endurance athletes have heard the rule: nothing new on race day. People apply it to shoes, breakfast, kit. The rule extends to your fuel. A gel you have never trained with is something new on race day, no matter how well-reviewed the product or how natural the ingredients. The only way a gel stops being “new” is repetition, in training, at the intensity you will race at.

What “using gels in training” actually means

It does not mean taking a gel on every easy run. On a short, low-intensity session your body does not need the carbohydrate, and forcing it in trains nothing useful. It means rehearsing your race fuelling on your race-simulation sessions — the long runs, the tempo blocks, the brick sessions that resemble what you will actually face. Same gel, same timing, same intensity, ideally the same time of day and heat.

Where honey gels fit

Honey delivers carbohydrate as naturally occurring glucose and fructose rather than a single sugar type.^[3] Because those two sugars use separate intestinal transport routes, a honey gel is already the kind of multiple-transportable-carbohydrate fuel the gut-training literature is built around.^[4] But composition is not a substitute for practice. The point of training with it is that your gut, specifically, needs reps with this fuel before race day asks it to perform.

What to do instead

Fold your race gel into your race-simulation training. Work out your hourly carbohydrate target with the Race-Day Fuelling Calculator, then rehearse that intake on the sessions that resemble your event, building up gradually. For the pre-start fuelling window — which also deserves rehearsal — see The Pre-Load Protocol.