Yes you might have bene exposing yourself to metabolic damage only eating 500 calories a day, not least an increased risk of anaemia, bone thinning problems, repressed immune system, sleeplessness, lethargy etc.
You would have then potentially gained weight if you added significantly more calories back in as the body could see some of those as excess calories.
Also 1lb of added muscle burns an extra 45-50 calories per day, so losing muscle could create the opposite effect.
This is a plan I post sometimes for people, so it might help you
Breakfast
Option 1.
Bowl of Whole-grain Cereal and scrambled Eggs, (2 Egg Whites + Yolk)
Option 2.
1/2 Protein shake, small portion of Nuts, (excluding higher carb ones like Cashews, Chestnuts and Grapenuts), + Apple. Give the Apple 10-15 minutes to digest to improve digestion.
Snack
Option 1.
Portion of Turkey + Orange
Option 2.
Small Portion of Peanuts, some Chicken + Raw Carrott.
Lunch
Option 1.
Large Beef Sandwich with trimmings, I.E. Tomato, Lettuce, Cucumber etc.
Option 2.
Bowl of Chicken Soup, + Pot of yoghurt.
Snack
Option 1.
Turkey + Cashews
Option 2.
Ham + 2 large Tomatos
Dinner
Option 1.
Pork with mashed Potato.
Option 2.
Chicken and Rice
Option 3.
100g Halibut + Broccoli
Snack
Option 1.
Beans on Toast
Option 2.
Ham Sandwich, no trimmings.
Easy on the bread with both options.
You could add a few things to certain meals, like Sea Salt, Cracked Black Pepper. Parsley, Mustard, Herbs, Garlic.
