Food can be single items (chocolate, grapes, apples, bread) it applies to anything that you can eat. Meals are breakfast, lunch, dinner. If you were going to a restaurant you might say "Shall we go out tonight for a meal"

MEAL (BREAKFAST, LUNCH, DINNER, or SNACK) FOOD (FRIED CHICKEN, POPCORN, STRAWBERRY, ANYTHING THAT WE EAT)