Training on an empty stomach;

Running first thing after waking, before fussing with making food, or any other task on the to-do list, is a great mental trick to make sure that training happens. Some may call it “eating the frog”, or “putting first things first”. By training first thing, there’s less risk of interruption, of an infant requiring attention, or any number of derailing happenstances.

There are, however, considerations to training first thing. You won’t have a chance to prepare your body in the same way that you would training later in the day. The main considerations are hydration and nutrition. Hydration can be addressed by remaining hydrated throughout the day, as a habit, and having a small glass of water (8-12 oz) immediately when waking. Consuming water during exercise is an effective way to address dehydration, too.

But what of nutrition? When waking, your body is in a fasted state; overnight is typically the longest that many go without consuming food. Whereas through the day, we consume calories to fuel, overnight the body uses a handful of alternative metabolic pathways to keep up blood sugar. The predominant pathway is called gluconeogenesis, and it occurs in the liver. Liver cells essentially break up the energy larger molecules (including glycogen, pyruvate, glycerol, and lactate) into glucose. This glucose is returned to the blood, and is used by the rest of the cells in the body.

Critically, gluconeogenesis occurs much more slowly than the rate one can digest simple carbohydrates into glucose. Gluconeogenesis is modulated by hormones, and the rate of change in glucose production by the liver is small. Changes tend to be measurable in hours, not minutes. When you consume food in the morning, and break your overnight fast, gluconeogenesis is pretty quick to down-regulate, and will be slow to return.

Now, consider your workout. You’ve got two options for fueling:

1. Don’t eat at all. Maintain liver glucose production as high as it can, and know that if you want to engage in high intensity activity (anything beyond lactate threshold), you’ll likely need to consume the majority of carbohydrate your workout requires.
2. Consume a fast digesting meal, around the amount of carbohydrate required for your first hour or so of activity. Give your food time enough to digest and raise your blood sugar, before engaging in activity.

What you *do not* want to do, is consume just a small amount of calories, particularly just before exercising. If you consume food, your liver will reduce production of blood glucose, and when you exercise, you’ll find effort challenging. Food consumed has to be enough to sustain your activity level until you consume more. A mouthful of maple syrup may be enough to fuel for ten minutes, but after that, you’ll feel quite poor.

So, when it comes to training first thing, pick one. Go totally fasted, and keep your activity moderate. Or get sufficient calories in your body to fuel strenuous exercise. This sounds simple, but if you habituate to training fasted first thing in the morning, and you schedule a strenuous activity, it’s easy to feel that no other change is required. That’s a recipe for a tough workout.