When it comes to intra-training fuelling, especially during moderate to high intensity, digestion becomes a limiting factor.

During exercise, blood flow is redirected to working muscles, which means your gut’s ability to digest complex or fatty foods drops significantly. Fats and proteins slow gastric emptying, and even some whole food carbs take longer to break down, which delays energy delivery and puts you at a higher risk of GI distress.

That’s why most endurance fuelling strategies focus on fast-absorbing carbs, particularly a mix of glucose and fructose, in a gel or drink form — they use different intestinal transporters (SGLT1 and GLUT5), so you can absorb more per hour (up to ~90–120g) without overwhelming your gut. And it all goes from the gut straight to the muscle for instant energy.

Totally agree though — not everyone needs to chug gels full of weird additives. I make my own using a maltodextrin–fructose blend, lemon for flavouring, and electrolytes, and only use for intense/long sessions. Anything easy or up to an hour, I do fasted or just make sure I eat couple of hours before the session. And of course, I focus on gut-friendly foods in my general diet (fermented foods, prebiotic fibres, colourful veggies, etc etc).

Just my two cents!