Exploring the best time to exercise for weight loss, examining fat burning in a fasted state vs. a fed state, the role of carbohydrate metabolism, and the impact of exercise timing on glycogen and insulin release. Analyzing the effects of pre-meal and post-meal exercise on weight loss, and discussing optimal timing for exercise and blood sugar control in individuals with diabetes.
Exercising before a meal leads to more fat being burned during the exercise compared to exercising after a meal.
Exercising before a meal may lead to sustained fat burning throughout the day, even with low to moderate intensity activity.
Deep dives
Exercising before a meal leads to more fat burn during exercise
Multiple experiments have consistently found that exercising on an empty stomach, before a meal, results in more fat being burned during the exercise compared to exercising after a meal. On average, low to moderate intensity activity before a meal burns about three grams more fat than the same exercise performed after a meal.
Timing of exercise affects 24-hour fat burning
Research suggests that exercising before a meal may lead to sustained fat burning throughout the day. In a study from Japan, participants who exercised before breakfast burned nearly 90% more fat over a 24-hour period compared to those who exercised after lunch. Timing matters even for walking; exercising before breakfast resulted in 717 calories of fat loss in a day, while exercising in the evening after dinner only resulted in burning off 446 calories of fat.
Pre-meal exercise and glycogen depletion promote fat loss
Exercising before a meal, when glycogen stores are lower, can lead to greater fat burning throughout the day. During fasted exercise, the body relies on breaking down glycogen and fat for energy, resulting in more fat loss. The depletion of glycogen stores acts as a trigger for increased breakdown of fat. Timing matters, with as little as six hours of fasting before exercise being sufficient to trigger this effect.