Is it good to run on an empty stomach in the morning?

Generally speaking, running on an empty stomach in the morning is beneficial; however, excessively long running sessions may be detrimental. A detailed analysis follows:

When running in a fasted state, blood glucose levels are relatively low. To meet the energy demands of running, the body accelerates fat breakdown for fuel. This occurs because insulin secretion decreases during fasting, and insulin is a hormone that inhibits fat breakdown. From a fat-loss perspective, morning fasted running may enhance fat oxidation, thereby aiding individuals seeking weight loss to achieve their goals more efficiently. Additionally, morning running stimulates the release of neurotransmitters such as endorphins, which can improve mood, leave one feeling invigorated post-run, and boost daily work and study performance.

However, prolonged running while fasting poses risks. Due to insufficient carbohydrate availability, hypoglycemia may develop, leading to symptoms such as dizziness, fatigue, palpitations, and cold sweats—and, in severe cases, syncope. Furthermore, during fasting, the gastrointestinal (GI) tract is empty; running-induced physical motion—including jostling and vibration—can disrupt normal GI motility and potentially cause mechanical injury to the digestive system, such as gastric spasms.

Therefore, when engaging in morning fasted running, individuals should tailor their exercise plans according to their personal health status and avoid excessively long runs to safeguard overall health.