VO2 max is the optimum rate at which the oxygen is efficiently used by the body during exercise, When there are longer breaks between workouts, the body's VO2 max begins to drop considerably.
The more fit a person is, the more their body shows signs of de-training than someone who is irregular in working out.
A study shows that after three days of inactivity, the blood sugar levels remained elevated even in healthy, young individuals.
If your days off from the gym turn into a couple of weeks, enjoy it, because you'll be better off when you return mentally and physically.