Lightheaded While Working Out

I've recently stepped up my workout routine and am doing an hour straight on the Elliptical machine at the Y,. I've been noticing lately that when the 45 minute mark starts approaching, I begin feeling incredibly exhausted. And not just my leg muscles, but my entire body feels so exhausted that I think I'm going to pass out. I've decreased calories as well, but not anything extreme; I'm still consuming about 1200 a day. I'm not an 'unfit' person and have been working out regularly for the past year, but ever since I've increased my activity level, the symptoms have started. Any ideas on how to make this go away, or why it's happening?

You didn't post your stats (height, weight, age), but 1200 calories is a very small number.Besides on such a smaal number of calories, you shouldn't decrease calories and intensify your workout at the same time.

If you want to exercise more, eat more (healthy foods). Eating 6-7 light meals a day will keep your metabolism up and your workout will be more effective.

I'm 5'3, 135 lbs...thanks for the reply; definitely a great suggestion.

Try a different machine halfway through your workout..  The elliptical makes my feet fall asleep, so I'm wondering if it's a circulation issue making you lightheaded.

I'll give it a shot - thanks!

How is your breathing & HR at that point?  Do you find it harder to breath when you get to that point or feel like your gasping for air?  Do you feel like your veins are going to pop out of your neck & your heart is going to explode out of your chest?  Ok, those are a little extreme, but you get the point.  The dizziness could be that you're simply working too hard for your body. 
-You may need to reduce your time and step it up slowly from 45 minutes to 50, then to 55, then to 60. 
-Or start out at a slower place or with a lower resistance or reduce the intensity/resistance once you get to the point you feel weird. 
- Or eat more... your body needs fuel to run.  1200 calories is low, but then subtract the 300ish calories your burning and you're only taking in 900 calories (or less depending on the calorie burn).

Even back when I used to run marathons this would happen to me.  I regularly ran 7-10 miles a day and there were days when I wouldn't be able to get past 3 or 4 because I was so tired.  In my case even though I was very very fit I wasn't eating nearly enough and my body just couldn't handle it.... I basically ran out of gas - no fuel, no energy.

Sounds to me like you need to make sure you have a shake or sports drink 1/2 hour before you hit the gym...the tank may be going empty on you.

I would say you probably aren't eating enough, as 1200 is a minimum and 45 minutes of cardio is going to be hard on minimum calories.  You may also be dehydrated if you aren't drinking in those 45 minutes.  Make sure you have some water on hand to sip!

my heart rate doesn't ususally go past 170 or 180, but stays level at 150 or 160; nothing out of the ordinary. I'll definitely try the sports drink thing and lower the time I'm working out for a while, just to see if it improves. Any tips on good sports drinks that aren't filled with sugar??

As a diabetic, I have to load sugar during my exercise sessions. Even if you are not diabetic, you are lowering your blood sugarto a point that may cause dizziness or light-headedness.

Proteine shakes are only 110 calories per scoop so Theres really not a lot of sugar to bother ur body. But on the good side it's loaded with great stuff for ur body.Feed those muscles