This Guardian article has some interesting information on the impact of convenience food. It follows a report on the carbon footprint of certain sandwich fillings. This connects with work that we do on Food Miles and the wider geographies of food.

There's a podcast that you can listen to here as well.

It reminds me of the nef research on fast food and its impacts from some years ago.
An Inconvenient Sandwich was the name of the report, and it focussed on the fast food sector in general. 
A reminder of the wider importance of our food choices, which we spend billions of pounds a year on.