middle-age spread vs spare tyre

middle-age spread

noun
  • Belly fat that develops in middle age. 

spare tyre

noun
  • A large paunch and rolls of fat around the waist. 

  • An extra tyre carried in case one of the vehicle's tyres is damaged or deflated. 

How often have the words middle-age spread and spare tyre occurred in a corpus of books? (source: Google Ngram Viewer )