Yep, don't forget, being a westerner, you probably tend to view the mind as separate from the body. It's not and never forget that. If you're staying up that late two things are happening.
1. You are staying up way past your meal limit. This isn't totally bad when you're more stable but can be disastrous when you're just starting. If you keep eating you should be okay, but it's best to avoid staying up past 12:30 at the latest and getting up around 8. You want at least 7 hours of sleep, 8 is best though.
2. The most important thing is that whatever you do mentally will and always drains sugar. When you workout, sure, you can see your body losing sugar that way. But few people realize or even believe when they first hear it that the brain uses exhorbitant amounts of sugar
whatever it may be doing. If you're reading, it uses a lot more than just laying and watching tv, but it's still using it, staying up that late used up a ton, I bet my sugar balance on it!