Steak displaying that its about 50% effective because I ate it too much without trying other food (requires AppleSkin).
When hovering the lunch bag in the inventory you can see its contents and some info on the selected food item.
Using "/solstick stomach" will print your recently eaten foods and gives a summary on how that changes the effectiveness of your food.
The interface when holding right click while the lunch bag is in your hand and closed. You can select a different food while this is open by using the scroll wheel.
The crafting recipe for the lunch bag. Gotta get them cocoa beans first.