hi bridie as long as you have bolused correctly for the carbs you are eating with each meal you can eat whenever you want you dont have to stick to 3 meals a day as long as you inject for what you eat at the time
I try to have dinner at roughly the same time every day in order for my liver to kick in at roughly the same time every day, other than that I don't see the point in having a set number of injections per day or set times per day where you have to eat or inject.
I am a grazer - I eat when I want and this is often more than 3 times a day.
I am also slim so weight loss is not a problem - if anything I have the opposite problem and grazing seems to help.
When on MDI there is no restriction on when to eat. You can have 6 meals a day; you could have one meal a day.
As long as you can calculate how many carbohydrates there are in your food, you can eat what you want. You can have a roast with potatoes, parsnips, yorkshire pud, ... one day and a salad the next. Your insulin dose is likely to be different but you will learn how to calculate this.