Should you weight train fasted?
For those who are interested in building muscle (it should be all of you), it’s best to avoid training completely fasted. Here’s why: Building muscle involves increasing protein synthesis while reducing protein breakdown. The mTOR signaling pathways, which promote muscle growth, compete with the AMPK pathways, which lead to protein breakdown. Cortisol, a hormone that supports AMPK, competes with mTOR by encouraging protein breakdown. Think of it as a tug of war between the two systems. Cortisol's primary role in a fight-or-flight response is to mobilise energy by breaking down glycogen and fat, which helps the body cope with stress, including a demanding workout. Training on an empty stomach can elevate cortisol levels much higher during intense exercise, leading to increased protein breakdown and decreased protein synthesis. To support muscle growth and preservation, consider consuming some carbohydrates, in the form of milk sugar if you’re carnivore or a tablespoon of honey, before your workout. This provides the energy needed and helps keep cortisol levels in check, promoting more protein synthesis. If the body has circulating sugar accessible, it will utilise that first—thus not raise cortisol as much as if it would on a completely empty stomach. You're welcome.