If you want to burn more fat during your morning workout, do it before your breakfast. Exercise physiologists wanted to see how a morning workout affected food intake and fat burning.
To evaluate, they had 12 fit males exercise on a treadmill at 10 AM either before or after eating breakfast. Following the exercise, all study subjects were given a chocolate shake recovery drink and, later in the day, they were served a pasta lunch and asked to eat until comfortably full. The researchers noted that morning exercise did not lead to an increase in appetite or food consumption later in the day. In addition, those who exercised before eating breakfast burned 20% more fat relative to those who had a pre-exercise morning meal.
This makes perfect sense given that body stores of glucose will be at the lowest after an overnight fast. If muscles run low on glucose, they will turn to fat for energy.
(British Journal of Nutrition January 24, 2013; 1 DOI: 10.1017/50007114512005582)
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