I eat frequent, small meals, whenever hungry. The size of the meal = whatever alleviates that feeling of hunger--and not a bit more.
What to eat? Anything not processed. Basically as our ancestors did, when virtually all ethnic groups were fairly lean and strong.
Try to eat lean, but listen to your body.
If your energy is low, adjust your diet until you reach equilibrium.
I'm not a nutritionist, but this works for me.