Hi Michik, I am no specialist, but I have been exercising regularly since many years now. I stopped paying too much attention on eating around workout sessions. I eat 3 meals a day and try to make sure I don't eat too much just before exercise, which I often ignore as well
Since having diabetes I stopped 'feeding' myself all the time. In addition, I am not eating large amounts of protein, as my body would turn the excess into glucose. Hence, I ditch fancy protein drinks. In terms of energy, I expect my body to be able to handle exercise with and without food before and after. I suggest you try the gym and different diets, and, just with general diets, find out what works best for you.