You’ve probably heard the term ‘fasted cardio’ used when cardiovascular exercise takes place without consuming any food since the previous evening. The idea is to use the body’s fat stores for energy, but a study published in the American Journal of Physiology: Endocrinology and Metabolism suggests this might not be the best approach.
Researchers at the University of Bath tested the blood glucose and muscle glycogen levels of 12 healthy male subjects after an hour of cycling. On one occasion, they ate a bowl of oatmeal prepared with milk 2 hours before the workout. On another, they didn’t eat anything.
Eating breakfast increased the rate carbohydrates were burned during exercise. Not just the carbs consumed at breakfast, but also carbs stored in muscle as glycogen. Having breakfast before exercise also increases the rate food consumed after training is digested and metabolized.