Your body adapts to change fairly well, but your metabolism isn't going to change as fast. It takes several weeks/months of repetition to get measurable response from your body, but even then it's still far from turning itself around.
Get more sleep by getting to bed earlier, eat a small meal before your workout, try to get in a bit of protein just before your workout and something for energy that isn't loaded with sugar/caffeine or otherwise detrimental to your health. Do your workout, don't forget to eat healthy and often, make sure you don't get too few calories per day, and get plenty of rest. You'll notice a difference in no time.
"It is easier to build strong children than to repair broken men." ~ Frederick Douglass