It may also be caused by any number of physiological problems including but not limited to head trauma and/or medications you may be taking. I know that one of the side effects of the sleep drug Ambien is that it can deaden (while taking the drug) taste receptors.
I have the same problem. I am on medications and I have a problematic thyroid. There is a number of reasons that this could be, I would definitely mention it to my Dr.
Most people don't realize that the ability to "taste" is strongly related to your ability to smell; hence, when we have colds, the ability to taste food is diminished. You may be zinc-deficient; DON'T go "overloading" on zinc. Take the recommended amount listed on a bottle of zinc tablets. IF the zinc doesn't help, Get Thee To A Doctor!
Physically its usually due to having a cold. A blocked nose can completely kill your sense of taste and smell. If you have got a cold you should see your doctor to see if there's another cause
Same thing happens with me when there is something new to eat or drink. Few people take lot time to develop taste for different foods. It means that they don't like innovation in eating items. You might be undergoing same thing. But your case is different as you are saying that you can't able to taste any of your food. There is some psychological factor involved. You might feel that the food placed in front of you is not very good that is why you do so.