Your body can’t use protein as easily for energy so your probably experiencing low blood sugar, to avoid this you either need some low GI foods a while before you work out or a small amount of high GI foods right before you workout.
If you’re trying to loose weight then it’ll just be a side effect since you’re trying to keep your blood sugar low, if you’re just trying to stay fit or get stronger then don’t sweat the little extra food as working out will use it up.