This depends entirely on your meat source imo.
Vegetables don't really do shit and your body will process them lightening fast. But in most meals you're always going to have a protein source and thats what usually fucks with digestion.
If you eat fish it takes your body about 2 hours to digest.
If you eat chicken/turkey is generally takes 5-6 hours to digest.
If you eat red meat, hamburger, sirloin steak, london broil, it can take your body up to *24* hours to actually digest. A lot of people don't understand that.
Although you will get 90% of the other shit out of your stomach in a few hours, you still have a smaller amount being digested much much later in the day.
The key is to know really how long it takes your body to digest certain foods. If I eat a salad, thats 90% lettuce, and 10% red meat, 90% of that meal will be gone in like an hour.
If I eat a meal that is 10% lettuce, and 90% red meat, even 6 hours later you still have A LOT of undigested meat in your stomach.
Also, fats prob take longer than ANYTHING for your body to digest. This is why you can down a gallon of beer in 1 hour (body can process carbs somewhat fast - well only really if they're simple not complex carbs) but if you try to down a gallon of milk in 1 hour its NOT HAPPENING NO MATTER WHAT. You're likely to not even get a half a gallon in your stomach.
So foods that are hi in fat, or dense meats in general will fuck up an opiate high even hours and hours later in the day. But if you stick to fish and light carbs, in as little as 1-2 hours most of it will be gone.
I generally don't eat at all, and binge one massive meal later in the day far after I take my dose. Its the most terrible thing you can do. But I seem to care more about getting high then being healthy.