It's pretty specific to your circumstances. For example, the other day I only had one meal because I had indigestion and didn't even want food. That one day did not cause me to go on a ravenous binge.
In fact, some people do better with hunger control if they eat a few larger meals in a fixed period of time. Some people do not, however.
And even if one meal a day might be ok, just a sandwich sounds a little lacking in nutrients and protein. If you're going to that low calorie you have to be really careful or you're entering the malnutrition danger zone. It's the area where you should be talking to your doctor and recording exactly what you eat so you can figure out if you're missing something.