Nothing is forbidden in our home, except artificial food (sweeteners, fake fats). We cook mostly from scratch, and maintain a balanced diet of meat, veggies, fruit and some rice, potatoes or other starch to round it out. Fish is a favorite food, as is fresh fruit. Dessert is an occasional treat - not a staple of our diet. Bread is whole grain, and I'm a great fan of nuts and whole grain hot cereals. We've recently switched over to raw milk from a local farm to provide a more natural product for our sons. Every member of the family takes vitamins.
Unlike many folks, we've stayed with butter and full fat milk (in addition to olive oil). I put real cream and sugar in my coffee, and cook our eggs in farm fresh butter. It goes well with bacon, of course! There are good minerals in animal products, and fat soluble vitamins need some fat to be properly absorbed by our bodies. Since none of us are overweight, the whole family enjoys the flavor - in moderation of course. The boys are healthy rascals of 7 and 10, rarely get sick, and have plenty of energy to give us grey hair.
One other consideration is that low energy can be a sign of depression. If you address your poor diet, get more sunshine and exercise, I would expect your energy level to improve. If it doesn't, there may be other chemical imbalances at work.
A final thought, is to be careful of the food pyramid. As you do your research into balanced nutrition, you will encounter the famous food pyramid. Our kids come home with projects from school surrounding this pyramid. It recommends a pile of starches as the base of the pyramid. This is somewhat controversial now, and it has been suggested that the heavy reliance on starchy foods is making Americans fatter.
I will go to the Doctor and try to rule some things out, and see what might be discovered.