The good news is that there's no benefit to working out in the morning over the evening, or vice versa. Two things to keep in mind, though: Experts suggest not exercising too close to bedtime, since some believe the increase in body temperature and metabolism could interfere with sleep. Additionally, working out in the morning provides you with the benefits of increased blood flow throughout the day, which helps with mental and emotional capacity.

Source: http://www.webmd.com/diet/features/what-eat-before-during-after-exercise?page=3