Energy Gels 101: how they work, why use them, and which are the best?

Recently I have been increasing the number of energy gels I consume as part of my weekly training regimen. I find that it really helps supplement my energy levels when I can´t find the time for more than three big meals per day, especially on my high volume training days. They are also invaluable on long training runs or rides, when you need to eat on the road to refuel your muscles and avoid the temptation to cut your training short.

How do energy gels work?

When you workout you are using either glycogen (carbohydrate) or fat for energy. Most of the time we are training at an intensity that will use up our carbohydrate stores, and because we can only store a limited amount of muscle glycogen (typically 90 minutes of muscle glycogen when running half marathon pace and two hours worth at marathon pace) , we tend to deplete those when endurance training. The energy gel was designed as a convenient way to supplement your glycogen stores, and replenish your energy levels.

Why use ENergy gels?

Although designed to replenish your muscle glycogen stores, in fact, the time from ingesting a gel until availability of glycogen is rather slow, with the glycogen needing to be digested, then absorbed through the intestinal wall before it can be absorbed and used by the muscles (tip: use them well before you feel like you "need" one).

Although this is the case, glucose is also stored in our blood, and when you eat a gel, you will often feel an effect fairly soon after. That is unrelated to the muscles, but is the effect you are feeling on your brain, which also relies on glucose to function properly. When you partake in endurance training your muscles absorb more blood glucose, resulting in a depletion in glucose for the brain. The gel may help your mind feel more energised, even if it doesn´t stop your legs from feeling like they have hit the wall.

Which energy gels are the best?

This is such a personal question, and one that is hotly debated online. There are literally hundreds of different gels on the market, and selecting one is usually a matter of trial and error.  For many people it is a matter of finding one that doesn´t upset your stomach. There are different types of gel contents, for example with and without salt or caffeine, and the flavours are almost endless. I recently discovered (via my Instagram post below) that there is even a beer-flavoured gel on the market! 

You can see below when I asked my Instagram followers which energy gel is the best, I got 38 comments, and a wide variety of answers. Again this shows how personal it is, and how important it is to try out different types to find out what works for you.

I have been working my way through the different types of gels, trying out different types and flavours. My favourites at the moment are SIS Blackcurrant and GU Salted Caramel, the latter of which has caffeine and is simply delicious. I have to stop myself eating them for dessert. 


Consuming gels (or carbohydrates in general) during long workouts and races improves performance, more through the effect on your blood glucose levels and the impact on your brain than anything else. The quantities you need are thought to be around 40 to 60 grams of carbohydrate per hour, with the gels I am using both containing 22 grams. Which gels are your favourites? Let me know in the comments below and I´ll try them out!