With what you had mentioned, I understand that you have been eating one meal a day and there is an inhibition of putting on weight. This may be your perception indeed. If you are not eating due to fear of putting on weight, do consider to change your approach. Eat balanced-diet and get into the habit of regular exercise of your choice. There will no guilt feeling of eating. But if you are not eating due to loss of appetite (anorexia) implies that hunger is absent. A brief period of anorexia usually accompanies almost all sudden illnesses. Long-lasting (chronic) anorexia usually occurs only in people with a serious underlying disorders. If this is the case, immediate go for medical intervention and get yourself diagnosed to rule out any complication