I've read a lot of stories over the years, and Google is not being kind to my search terms (it probably flagged something with NSA or Homeland Security, too).
The book I'm thinking of is set in an alternate reality, in the future for when it was written but in what is now our past. Overpopulation is a concern with not much food available (compared to the population). The government takes volunteers who are offering to end their lives, and then those volunteers are converted into nutritional pills that are handed out to the rest of the population as food.
I was originally thinking it was 1984, but others have contested that.
I have not read Make Room! Make Room!, by Harry Harrison, from which the movie Soylent Green was adapted (I have not seen this movie either).
I would have read this book circa 2008-2010, but it was definitely an older book (pre-90s). If I remember correctly, this was during my "Top 100 books" phase, where I was catching up on the top-rated books. I'm assuming it may be on a list such as this, and I remember some of the other books were from Hemingway, The Catcher in the Rye, The Great Gatsby, etc.