Some people are just sensitive to certain carbohydrate sources, myself included. I now only have fruit either immediately before or after training, as I typically keep carbohydrate content fairly low except on training days, and except near times I'll be lifting. I can't eat much for carbohydrate sources except when needed, otherwise, I'm bloated, sluggish, and feel less than good most days. Everyone is different, so it's always a personal issue to see how you fare, not everyone is going to respond to the same foods or macronutrient ratios the same way. There are people here who seem to thrive on fruit, some who can pound down plate after plate of pasta, etc., but some who are like myself who have to be VERY careful about carb sources and intake if we're out to try and reduce bodyfat.
So far, I've managed a slow-and-steady drop of about 15 lbs. of pure fat in the course of 4 months without any cardio (save for about 4 nice walks I've taken in the past month), gotten considerably stronger, and without any real restriction on calories, doing only weight training and eating plenty to never be hungry with 3 good-sized meals and 2-3 snacks over the course of the day. It took a lot of experimentation to find what has been working for me, but if you try all logical approaches at some point, you'll know just what's going to work.
If you're feeling headachey or cranky from lower carb intake, I'd suggest checking to see if you can locate any vegan glucose tablets at your local pharmacy. Some brands are vegan (though, most will have artificial colorings in them, they aren't totally natural), usually 1-2 tablets can help bring you back to life again without being carb-heavy to slow the fat loss effect of a lower carbohydrate diet. When I've done really low carb plans in the past (100g or less per day), I've relied on glucose tablets to get me through my workouts, usually taking 2 before training and sometimes 2 afterward along with a post-workout shake. That, or I'd make sure to eat a pear or banana before training if I was going to have a fruit-based carb source, that worked well for me, too, and helped keep me fueled and from crashing too quickly. Oatmeal worked well, too, for pre-workout energy without being too high in carbohydrates. It doesn't take a LOT of carbohydrates to stave off the bad feelings that come with reducing carbohydrates too far, and the first few days tend to be the toughest, but once you adapt, you may just feel better for it. I know now that I can't consume 50% or more of my calories from carbohydrates and feel remotely energetic or motivated (meals high in carbs just make me want to go to sleep many times), so I've learned to keep them at around 30-40% max for my intake and that seems to do fairly well on days that I'm training. I usually cut carbs considerably on my "off" days when I'm not at the gym, sometimes as low as 20-25% occasionally, it all depends on the day.
Lower carb dieting isn't for everyone, but some of us do respond better to it when our bodies have decided that carbohydrates aren't always our friend!
"A 'hardgainer' is merely someone who hasn't bothered to try enough different training methods to learn what is actually right for their own damned body." - anonymous