500 calories is never enough, even if you are trying to lose weight! You need at least 1200 calories a day when you're well so a bit more probably while you're recovering. You don't have to eat "heavy" foods or foods you don't like in order to be healthy.

Use this calculator http://www.caloriecontrol.org/calcalcs.html to see what is the appropriate number of calories to eat for you. If you put in the healthy goal you want to weigh when you have lost your excess weight, it will tell you how many calories are needed to "maintain" that weight. So, if you eat that many calories now, you'll gradually get down to that weight.