Sebastian Sawe ripped open a carbohydrate gel sachet and slurped it five minutes before the start of the 2026 London Marathon. Sixty minutes later, he inhaled another one before smashing through the two-hour marathon barrier.

Sawe might have been the first sub-two-hour marathon runner, but he’s certainly not the first to be powered by an energy gel. It’s estimated that over 70% of marathon runners use gels.

Long before energy gels were a thing, endurance athletes used all sorts of foods to fuel their athletic feats – from sugar lumps and coffee, to chocolate, beer, wine and even egg whites and brandy.

But from the 1970s scientists caught up with athletic practice. Research demonstrated that carbohydrates were effective in fuelling prolonged endurance exercise, with foods containing glucose and fructose (forms of sugar) proving to be the most effective fuels.

Thanks to decades of research, athletes today can use energy gels to provide fuel. These are precise, scientifically-calibrated carbohydrates in the form of maltodextrin and fructose blends encapsulated in a hydrogel.

But while these modern gels promise fast energy and improved performance, not all scientists are convinced they live up to the hype – and for many athletes, they come with uncomfortable side-effects.

So are gels really worth it, or should athletes stick to simpler, if less glamorous, sources of fuel?

Fuelling with energy gels

When we eat a meal, our........

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