Intermittent fasting for athletes: Does it affect performance?

Over recent years, intermittent fasting (IF) has gained popularity, being promoted by many as a superior diet for weight loss, reducing inflammation, and improving metabolism. Many of these claims are backed by anecdotal evidence and historical practices, however, amongst the recreational and elite athlete population, there is little evidence to support these claims being beneficial to performance. We know training fasted means you are utilizing fat as a source of energy, but this isn't necessarily leading to loss of body fat. So let's get to the bottom of this topic, starting with fasting itself.

What is Intermittent Fasting?

Just as the popularity of IF has increased, so has the range of different methods of intermittent fasting. These methods are each aimed at limiting food intake for a certain period of time, to reap the supposed benefits.

One of the many types of time-restricted fasting is the 16/8 method, which involves fasting daily for 16 hours with a restricted 8-hour window to eat. With this method, people typically won't eat after dinnertime, and their first meal of the day is usually around lunchtime. Another type of fasting which is just as common is whole-day fasting, which includes the 5:2 method. This method involves complete fasting (or consuming no more than 500kcal/day) for 2 days out of the week, which can be consecutive days or split over the week.

The bottom line is that IF is just another way to create a calorie deficit. For the purpose of weight loss, it is important to note that studies