When your digestive system is not so busy breaking down food, you get better results - but anything is better than not practicing at all. A lot of times when I come home late at night, I'm very hungry & I need to eat. So I still start practicing maybe 1 hr after eating. One other thing I do is sometimes I just practice one movement (like moving of yin/yang) for a while and end my exercise. You can also do one exercise for a while at different times of the day as you get smaller slots of free time.
