What Happens When You Work Out On An Empty Stomach

When it comes to exercise, everyone has their own routines and preferences, including a favorite time of day to work out. Some like to exercise during their lunch break, while others prefer to wait until the end of the day to get their sweat on after work. And then there are those who exercise first thing in the morning, usually on an empty stomach. But what exactly happens when you work out on an empty stomach? And why do people do it?

As Alexandra Cook, of The Sports Dietitian, told Cosmopolitan, "There can be some benefits exercising on an empty stomach, but it is very individual and goal dependant." She continued, "As we sleep, our stored carbohydrate (glycogen) naturally depletes, a bit like a tank of petrol reducing. If you exercise as soon as you get up without eating, you would have to rely on fat stores a lot sooner than if you had readily available energy to use from breakfast." In other words, working out on an empty stomach can actually contribute to fat loss, which explains the reason so many people choose to do it!

But unsurprisingly, there are some downsides to exercising on an empty stomach. "You might feel tired or edgy, and you won't be able to work out as intensely as you would have if you had eaten something," Douglas Paddon-Jones, a muscle physiology researcher and a professor of aging and health at the University of Texas Medical Branch, told TIME. And as a result, you probably won't be able to reach your full potential if you don't eat at least a little something before working out. "A light amount of food will help you get through the workout session more comfortably and with more energy," he argued. 

As will water. "The body is usually not well hydrated when first getting up from a night's sleep," exercise physiologist John Ivy, Ph.D, told mbg. So if you're going to try out working out on an empty stomach, make sure you have at least had a glass of water before you get started.