First off you are a male. It is very common to have a receding hair line as you age. It is possible that your nutritional deficiency may have had some influence.
If the hair loss is as a consequence of your poor diet, then it no doubted will grow back. If on the other hand it is due to genetics, then it won't. Time will only tell. To help stimulate the scalp to get the blood flowing that may help the hair growth - massage the scalp with your finger tips. Don't use any harsh shampoos.
Glad to hear that you are now on a healthy eating plan. If you do take any supplements, always follow the directions on the packet or as prescribed by your doctor. Some vitamins can cause damage if taken in excess - these are the fat soluble vitamins (these are Vitamin A and D as well iron, that I know about).
A lot of hair loss in men is down to genetics, so do take a look at your father and grandfather. It does not always follow, but in most cases it does.
My son was lucky that he got did not take after his father with think and thinning hair - he took after my dad that always had lots of thick hair, but receded in the front.
Personally, I wouldn't bother with the hair pieces. These days all sorts of hair styles are acceptable, but if you do feel so self conscious about it, wear a hat.