Ok, so ever since I was a kid I would experience these symptoms (I'm 31 now, 5'9 265 pounds). I've never really looked into it or went for testing about it. But here is what happens.
Sometimes when I eat a assload of sugar like a couple cans of dew and a bowl of cinnamon toast crunch, a 45 minutes to an hour later I guess I crash. I get very weak, and very shaky, sometimes I even feel sick to my stomach and if I don't eat something fast I would prolly pass out, although that has never happened. Once I eat something (has to be something like pizza, or pasta, a burger whatever) I immediately start to feel better. A sigh of relief.
Now this doesn't just happen when I eat a buttload of sugar, since I have been dieting more consciously to try and thin out this can occur if I say, a can of tuna, a salad with a tad of cheese, some fat free dressing and maybe some broccoli. So LOW carb. Then 30-45 minutes later same thing starts to happen, I get weak, shaky, sick etc.
So it happens either way, and some supplements I take like R ALA lower your blood sugar so I have to compensate with more carbs. And it just seems like I'm kinda stuck being 20-25 pounds over weight cuz I cant really cut my carbs without these symptoms affecting me. And its not that I want to cut my carbs out, but I am trying to lower them and take in more protein. I dunno, I will be scheduling a doctors appointment within the next week to see if I can shed some light on this and get some blood work done.