I was planning on listing several references and then talking about each one. After selecting a mere 20 articles, I decided that wasn't the smartest thing to do. So go do the research yourself. You'll find plenty references to how sleep deprivation hinders weight loss, athletic performance, and general health through jacking up hormonal responses and metabolism. I automatically think of unhealthy levels of cortisol, but this wasn't the only hormone that was brought up in my research. If I could spell out, IL-6 and the others, I would...ok, I wouldn't, I'm lazy. Hormones drive many functions in your body. If you screw up your hormone levels, you affect those functions.
A friend was recently wondering why her running performance and fitness levels were not improving. She is not getting much sleep at all. I told her to fix the sleep problem or accept the consequences. It may seem harsh to say that, but it's true. Your ability to get sleep does not rely on your choice in the matter. You may have a job that keeps you from sleeping, but you love the job and refuse to quit. That's fine. I just ask you accept the consequences. Your body doesn't care how you explain, rationalize, or prioritize not sleeping. It only reacts to the action.
I admit that there are nights I don't get good sleep. I make a decision on whether or not I will get any benefit from working out or if I'd be better off sleeping more. There are also times I know my afternoon is booked, so I must workout in the morning. I either don't workout that day or I workout knowing that my performance will be far from stellar. Then I work like hell that day to make sure I get enough sleep. Put sleep high on your priority list. Be the guy/girl at work labeled as "selfish" because you leave on-time to make sure you get things done and can go to bed in a timely manner. When you go to work the next day and ask people why they look like crap, it just may make you feel better for being called selfish.