Hard to say exactly w/out knowing more.
How much are you eating now? What are you eating? Are you eating before working out? How much water are you drinking?
All of those things could be a factor. I know that I *have* to have a snack before a really hard workout or I will get sick feeling. I can't eat a lot - a full stomach also makes me sick. But I need some carbs and some protein or I'll get woozy and nauseated.
I also get sick if I work too hard, no matter what I'm doing. I actually did it to myself tonight a little - I was doing HIIT on the elliptical and after round 5 I was really queasy. I didn't puke, but I felt like I might. So I toned down my 6th and final interval. I think it was a combination of too much exertion and too little water (I forgot my water bottle and so I didn't have any at the gym).
I do suspect that the hunger is from ramping up your workouts. Again, let us know what you're eating and we can maybe offer some suggestions.
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