One of the best ways to cut costs is to not cook for one, but to cook together with others. Then you can buy in bulk like the author suggested.
I live alone and I do cook for one. I probably spend more on food than most. However, I chose to live in a compact city with relatively low rents. This way I don’t need a car. I live in walking distance of supermarkets, health food stores, farmers markets and bakeries. I live 1 minute from a bus stop, 5 minutes from the main train station. What I spend more on groceries, I make up for in low rent and using public transport instead of owning a car.