I thought sugar was OK while you’re exercising
Depends.
When exercising intensely (ie short XC race), you are using your muscle glycogen stores, so when you eat sugar (or something else high GI) the insulin produced encourages your cells to take up glucose from the blood which is a good thing – getting energy back into your muscles quickly where it can be used.
However, insulin also inhibits the use of fat by your muscles, so if you are on a long endurance ride or even a long race you WANT to be burning fat, so sugar is to be avoided at first and then limited later. This is a vital piece of information I was previously missing.
My current approach is to not eat for several hours before a ride, so insulin levels are low, and then not within the first 45 mins so that you start off burning fat. I’ve found that after 45 mins I might have a gel but I seem to want to consume far less carbs than I would previously.
It also gets easier to go without, quite quickly. Yesterday i did a fairly stiff 2h15 ride at 7pm having only had a salad and a couple of coffees all day. Attempting Streatley hill in 39/25 did my legs in though!