I categorize spending in Quicken, so I can tell you:
In the last 12 months, for one person, I spent $228/month average on "groceries," which includes non-food items bought at the supermarket and bulk food items bought at Sam's club. I also spend (guessing more here) roughly $12 for restaurant lunch 20 days a month, so $468 a month total food costs (and often, I eat half and bring half home for dinner). Prorating my grocery costs, and guessing that half my lunches get split into dinner, I should be able to make my own lunches and all dinners and bring my monthly total down to $342, or about $85 a week, without being any more careful of what I buy. But lunch out with coworkers is one of my favorite splurges while I am employed at a good job.
I should note that I buy little meat, mostly chicken in large packages that I break up and freeze, or the same for hamburg (spaghetti sauce) or stew meat; but I do regularly buy some more costly things like lunch meats, cheese, and prepared deli salads, dark chocolate, nuts. I also buy fresh salad makings, and some of that goes to waste because of being a single person and being unable to use it all up before it turns.
So, I would say my example could be considered towards the high end compared to what is possible if you are more careful.