Running on empty in training can indeed be a useful way of keeping weight down if you need to, or staving off the wall in marathons and ultras. However, as you’ll discover, not having enough glycogen on hand can make the last third of a long run a challenge.
TR's expert Renee McGregor says: “Fasted training can be a useful method of utilising fat stores, but the common mistake many make is trying to do this session too fast. In order to mobilise your fat stores, you will need to run at no more than 60% of your maximum heart rate or a perceived exertion of 6/10.
“It is also important to build up to this slowly; start with 45 mins, building slowly up to 90 minutes to two hours. You should avoid doing more than three fasted runs a week, as this can depress your immune system.
“If you really struggle to run on empty then aim to consume a protein or fat-based breakfast prior to setting out. Some options include scrambled eggs with avocado, or even simply a handful of almonds. It is still essential to maintain the optimum pace to utilise fat stores.”