Do energy gels actually work, or is it placebo?

They work, and the mechanism is not subtle. But almost everything that goes wrong with gels has nothing to do with whether the science holds up. It is timing, dose and what your stomach will tolerate at 30km. Here is the honest version.

What is actually happening when you take one

You store roughly 400 to 500g of carbohydrate as muscle and liver glycogen. At marathon effort that is around 90 to 120 minutes of fuel. Once it runs out, your pace drops whether you argue with it or not. That is the wall, and it is a supply problem, not a willpower problem.

A gel is a dense, pre-digested dose of carbohydrate designed to reach the bloodstream fast. It does not top up glycogen mid-race. It spares it: the sugar you take in gets burned instead of what is in your legs, so the tank drains slower.

The number that matters: 60g an hour

There is a ceiling on how fast your gut can absorb glucose, around 60g per hour for most people. Take more than that from a single sugar source and the excess sits in your stomach, pulls water in, and gives you the sloshing and cramping that gels get blamed for.

The workaround is using two sugars at once. Glucose and fructose use different transporters, so a blended source can push absorption toward 90g an hour in athletes who have trained their gut for it. That is a race-day number for long events, not a starting point.

The reason people give up on gels is texture

Ask anyone who has raced with gels what went wrong and it is almost never the nutrition. It is the thick, cloying mouthful you cannot swallow properly while breathing hard, that coats your throat, and that you end up carrying half-finished because the next drink station is another kilometre away.

That is a formulation problem, and it is worth solving before you decide gels are not for you. yohemite's gel is built runnier than honey for exactly this reason. It clears in one go, mid-effort, without water to chase it. Whatever brand you land on, test the consistency in training before you commit to it on race day.

• 27g of carbohydrate per sachet, half of it from real Quebec maple water rather than corn syrup
• 110 calories (460kJ), a useful dose rather than a token one
• No water needed, which matters more than it sounds when the drink station is behind you

What about caffeine?

Caffeine does something different from the carbohydrate, and the two are worth separating in your head. Endurance fails in two places at once: you run out of fuel, and you run out of willingness. Carbohydrate fixes the first. Caffeine works on the second. It lowers perceived effort, so the same pace costs you less mentally in the stretch where that is what is actually slowing you down.

The practical rule: save it for the back half. A caffeinated gel at 30km does more for you than one at the start line, and one per race is plenty for most people. If caffeine keeps you awake or makes you jittery in daily life, it will do the same at 25km.

The mistakes that make gels look useless

1. Starting too late. Waiting until you feel empty means racing the 20-minute absorption delay. Start at 45 to 60 minutes and keep the interval.
2. Taking three at once. Stacking gels to "catch up" exceeds your absorption ceiling and gives you stomach trouble instead of energy.
3. Never practising. Your gut is trainable and it is also the thing most likely to fail on race day. Use the exact gel you plan to race with, in your long runs, at race pace.
4. Chasing with a sports drink. A gel plus a carbohydrate drink can quietly double your intake past what you can absorb. Pick one to carry the carbs and use the other for fluid.

When you do not need one

Under about 60 minutes of steady effort, your own glycogen has it covered and a gel adds nothing but sugar. Gym sessions, parkrun, a 45-minute ride. Skip it. Gels earn their place in long efforts, and a gym bag is not one of them.