I'll make this topic really simple. You need 7 - 9 hours of sleep each night in order for your body to run efficiently. Deprive your body of sleep and you'll have lousy fat loss. As a bonus, you also get muscle loss which lowers your metabolism. The reason for this is because without enough sleep the body stops producing anabolic hormones (Muscle Producing/Fat Burning Hormones; e.g. Testosterone and Growth hormone) and starts increasing the production of catabolic hormones (Muscle Destroying/Fat Depositing Hormones e.g. Cortisol). Also, you will lack the energy and focus to get through your workouts and it will also lead to overtraining as you won't be able to recover anymore. To top it off, there is research that indicates that a lack of sleep creates cravings and binges in addition to hardening of the arteries which leads to heart attacks. If you don't think that you have enough time to sleep, then turn off the TV and make the time!