I've had this problem for a long time, but now that I'm focusing on weight loss, it's a bigger deal than ever.
I feel like my body doesn't let me know that it needs food until too late. For instance, I wake up in the morning, workout, come back shower, etc, etc and my stomach doesn't growl and I don't feel hungry. Then as soon as I leave the house for school or work, I'm light-headed and angry, because I haven't eaten. Even then there is no feeling of hunger, just the effects of low-blood sugar. Usually I can only tell that I'm hungry when I feel faint/irritable or if I drink cold water and discover that my stomach is empty. On occasion my stomach will growl or my brain will say "Yo, eat some food, foolio!"
It's really annoying because I have to force myself to eat sometimes. Like now I'm forcing myself to eat some peanut butter and toast before my workout. Those of you who have struggled with food know that forcing yourself to eat is a terrible feeling. I'm also worried because eating greatly affects weightloss. Right now I'm eating way below (1400ish) my calorie recommendation (1700), which is already very low for my weight and activity. I know I should eat more, but what can I do if my brain doesn't let me know that my body needs food?
Anyone else have this problem? Any suggestions? I just got insurance this year (Thank you, Mr. President!), so if it doesn't get better in a few weeks, I'm going to see my doctor.

Now I can sense the hunger cues, and know when and what my body needs to eat.

Then there are days that I've eaten a plate full of food, and my stomach still doesn't feel full.