The BBC 2 Programme Trust Me, I'm a Doctor, looked at whether it is better to exercise before or after eating.
Turns out that it depends on whether you are male or female, because of the difference in male and female metabolism.
Women. Eat before exercising. Most of their fat burning occurs in the three hours after exercising. Eating up to one and a half hours after exercising can even stop fat burning.
Men. Eat after exercising. If men eat before exercising, they will use the carbohydrates in that meal first and may never switch to burning fat.
BBC 2 Programme Trust Me, I'm a Doctor, Series 4,
http://www.bbc.co.uk/programmes/articles/4glyLcrhgqQtPGQYM11l1YJ/the-big-experiment-how-can-i-get-my-body-to-burn-more-fat-without-doing-more-exercise
